This section dives into the details of Spring Boot. Here you can learn about the key features that you may want to use and customize. If you have not already done so, you might want to read the "getting-started.html" and "using-spring-boot.html" sections, so that you have a good grounding of the basics.
1. SpringApplication
The SpringApplication
class provides a convenient way to bootstrap a Spring application that is started from a main()
method.
In many situations, you can delegate to the static SpringApplication.run
method, as shown in the following example:
public static void main(String[] args) {
SpringApplication.run(MySpringConfiguration.class, args);
}
When your application starts, you should see something similar to the following output:
. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: v2.3.0.M2 2019-04-31 13:09:54.117 INFO 56603 --- [ main] o.s.b.s.app.SampleApplication : Starting SampleApplication v0.1.0 on mycomputer with PID 56603 (/apps/myapp.jar started by pwebb) 2019-04-31 13:09:54.166 INFO 56603 --- [ main] ationConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@6e5a8246: startup date [Wed Jul 31 00:08:16 PDT 2013]; root of context hierarchy 2019-04-01 13:09:56.912 INFO 41370 --- [ main] .t.TomcatServletWebServerFactory : Server initialized with port: 8080 2019-04-01 13:09:57.501 INFO 41370 --- [ main] o.s.b.s.app.SampleApplication : Started SampleApplication in 2.992 seconds (JVM running for 3.658)
By default, INFO
logging messages are shown, including some relevant startup details, such as the user that launched the application.
If you need a log level other than INFO
, you can set it, as described in Log Levels.
The application version is determined using the implementation version from the main application class’s package.
Startup information logging can be turned off by setting spring.main.log-startup-info
to false
.
This will also turn off logging of the application’s active profiles.
To add additional logging during startup, you can override logStartupInfo(boolean) in a subclass of SpringApplication .
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1.1. Startup Failure
If your application fails to start, registered FailureAnalyzers
get a chance to provide a dedicated error message and a concrete action to fix the problem.
For instance, if you start a web application on port 8080
and that port is already in use, you should see something similar to the following message:
*************************** APPLICATION FAILED TO START *************************** Description: Embedded servlet container failed to start. Port 8080 was already in use. Action: Identify and stop the process that's listening on port 8080 or configure this application to listen on another port.
Spring Boot provides numerous FailureAnalyzer implementations, and you can add your own.
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If no failure analyzers are able to handle the exception, you can still display the full conditions report to better understand what went wrong.
To do so, you need to enable the debug
property or enable DEBUG
logging for org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener
.
For instance, if you are running your application by using java -jar
, you can enable the debug
property as follows:
$ java -jar myproject-0.0.1-SNAPSHOT.jar --debug
1.2. Lazy Initialization
SpringApplication
allows an application to be initialized lazily.
When lazy initialization is enabled, beans are created as they are needed rather than during application startup.
As a result, enabling lazy initialization can reduce the time that it takes your application to start.
In a web application, enabling lazy initialization will result in many web-related beans not being initialized until an HTTP request is received.
A downside of lazy initialization is that it can delay the discovery of a problem with the application. If a misconfigured bean is initialized lazily, a failure will no longer occur during startup and the problem will only become apparent when the bean is initialized. Care must also be taken to ensure that the JVM has sufficient memory to accommodate all of the application’s beans and not just those that are initialized during startup. For these reasons, lazy initialization is not enabled by default and it is recommended that fine-tuning of the JVM’s heap size is done before enabling lazy initialization.
Lazy initialization can be enabled programatically using the lazyInitialization
method on SpringApplicationBuilder
or the setLazyInitialization
method on SpringApplication
.
Alternatively, it can be enabled using the spring.main.lazy-initialization
property as shown in the following example:
spring.main.lazy-initialization=true
If you want to disable lazy initialization for certain beans while using lazy initialization for the rest of the application, you can explicitly set their lazy attribute to false using the @Lazy(false) annotation.
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1.3. Customizing the Banner
The banner that is printed on start up can be changed by adding a banner.txt
file to your classpath or by setting the spring.banner.location
property to the location of such a file.
If the file has an encoding other than UTF-8, you can set spring.banner.charset
.
In addition to a text file, you can also add a banner.gif
, banner.jpg
, or banner.png
image file to your classpath or set the spring.banner.image.location
property.
Images are converted into an ASCII art representation and printed above any text banner.
Inside your banner.txt
file, you can use any of the following placeholders:
Variable | Description |
---|---|
|
The version number of your application, as declared in |
|
The version number of your application, as declared in |
|
The Spring Boot version that you are using.
For example |
|
The Spring Boot version that you are using, formatted for display (surrounded with brackets and prefixed with |
|
Where |
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The title of your application, as declared in |
The SpringApplication.setBanner(…) method can be used if you want to generate a banner programmatically.
Use the org.springframework.boot.Banner interface and implement your own printBanner() method.
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You can also use the spring.main.banner-mode
property to determine if the banner has to be printed on System.out
(console
), sent to the configured logger (log
), or not produced at all (off
).
The printed banner is registered as a singleton bean under the following name: springBootBanner
.
1.4. Customizing SpringApplication
If the SpringApplication
defaults are not to your taste, you can instead create a local instance and customize it.
For example, to turn off the banner, you could write:
public static void main(String[] args) {
SpringApplication app = new SpringApplication(MySpringConfiguration.class);
app.setBannerMode(Banner.Mode.OFF);
app.run(args);
}
The constructor arguments passed to SpringApplication are configuration sources for Spring beans.
In most cases, these are references to @Configuration classes, but they could also be references to XML configuration or to packages that should be scanned.
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It is also possible to configure the SpringApplication
by using an application.properties
file.
See Externalized Configuration for details.
For a complete list of the configuration options, see the SpringApplication
Javadoc.
1.5. Fluent Builder API
If you need to build an ApplicationContext
hierarchy (multiple contexts with a parent/child relationship) or if you prefer using a “fluent” builder API, you can use the SpringApplicationBuilder
.
The SpringApplicationBuilder
lets you chain together multiple method calls and includes parent
and child
methods that let you create a hierarchy, as shown in the following example:
new SpringApplicationBuilder()
.sources(Parent.class)
.child(Application.class)
.bannerMode(Banner.Mode.OFF)
.run(args);
There are some restrictions when creating an ApplicationContext hierarchy.
For example, Web components must be contained within the child context, and the same Environment is used for both parent and child contexts.
See the SpringApplicationBuilder Javadoc for full details.
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1.6. Application Events and Listeners
In addition to the usual Spring Framework events, such as ContextRefreshedEvent
, a SpringApplication
sends some additional application events.
Some events are actually triggered before the If you want those listeners to be registered automatically, regardless of the way the application is created, you can add a org.springframework.context.ApplicationListener=com.example.project.MyListener |
Application events are sent in the following order, as your application runs:
-
An
ApplicationStartingEvent
is sent at the start of a run but before any processing, except for the registration of listeners and initializers. -
An
ApplicationEnvironmentPreparedEvent
is sent when theEnvironment
to be used in the context is known but before the context is created. -
An
ApplicationContextInitializedEvent
is sent when theApplicationContext
is prepared and ApplicationContextInitializers have been called but before any bean definitions are loaded. -
An
ApplicationPreparedEvent
is sent just before the refresh is started but after bean definitions have been loaded. -
An
ApplicationStartedEvent
is sent after the context has been refreshed but before any application and command-line runners have been called. -
An
ApplicationReadyEvent
is sent after any application and command-line runners have been called. It indicates that the application is ready to service requests. -
An
ApplicationFailedEvent
is sent if there is an exception on startup.
The above list only includes SpringApplicationEvent
s that are tied to a SpringApplication
.
In addition to these, the following events are also published after ApplicationPreparedEvent
and before ApplicationStartedEvent
:
-
A
ContextRefreshedEvent
is sent when anApplicationContext
is refreshed. -
A
WebServerInitializedEvent
is sent after theWebServer
is ready.ServletWebServerInitializedEvent
andReactiveWebServerInitializedEvent
are the servlet and reactive variants respectively.
You often need not use application events, but it can be handy to know that they exist. Internally, Spring Boot uses events to handle a variety of tasks. |
Application events are sent by using Spring Framework’s event publishing mechanism.
Part of this mechanism ensures that an event published to the listeners in a child context is also published to the listeners in any ancestor contexts.
As a result of this, if your application uses a hierarchy of SpringApplication
instances, a listener may receive multiple instances of the same type of application event.
To allow your listener to distinguish between an event for its context and an event for a descendant context, it should request that its application context is injected and then compare the injected context with the context of the event.
The context can be injected by implementing ApplicationContextAware
or, if the listener is a bean, by using @Autowired
.
1.7. Web Environment
A SpringApplication
attempts to create the right type of ApplicationContext
on your behalf.
The algorithm used to determine a WebApplicationType
is fairly simple:
-
If Spring MVC is present, an
AnnotationConfigServletWebServerApplicationContext
is used -
If Spring MVC is not present and Spring WebFlux is present, an
AnnotationConfigReactiveWebServerApplicationContext
is used -
Otherwise,
AnnotationConfigApplicationContext
is used
This means that if you are using Spring MVC and the new WebClient
from Spring WebFlux in the same application, Spring MVC will be used by default.
You can override that easily by calling setWebApplicationType(WebApplicationType)
.
It is also possible to take complete control of the ApplicationContext
type that is used by calling setApplicationContextClass(…)
.
It is often desirable to call setWebApplicationType(WebApplicationType.NONE) when using SpringApplication within a JUnit test.
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1.8. Accessing Application Arguments
If you need to access the application arguments that were passed to SpringApplication.run(…)
, you can inject a org.springframework.boot.ApplicationArguments
bean.
The ApplicationArguments
interface provides access to both the raw String[]
arguments as well as parsed option
and non-option
arguments, as shown in the following example:
import org.springframework.boot.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.stereotype.*;
@Component
public class MyBean {
@Autowired
public MyBean(ApplicationArguments args) {
boolean debug = args.containsOption("debug");
List<String> files = args.getNonOptionArgs();
// if run with "--debug logfile.txt" debug=true, files=["logfile.txt"]
}
}
Spring Boot also registers a CommandLinePropertySource with the Spring Environment .
This lets you also inject single application arguments by using the @Value annotation.
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1.9. Using the ApplicationRunner or CommandLineRunner
If you need to run some specific code once the SpringApplication
has started, you can implement the ApplicationRunner
or CommandLineRunner
interfaces.
Both interfaces work in the same way and offer a single run
method, which is called just before SpringApplication.run(…)
completes.
The CommandLineRunner
interfaces provides access to application arguments as a simple string array, whereas the ApplicationRunner
uses the ApplicationArguments
interface discussed earlier.
The following example shows a CommandLineRunner
with a run
method:
import org.springframework.boot.*;
import org.springframework.stereotype.*;
@Component
public class MyBean implements CommandLineRunner {
public void run(String... args) {
// Do something...
}
}
If several CommandLineRunner
or ApplicationRunner
beans are defined that must be called in a specific order, you can additionally implement the org.springframework.core.Ordered
interface or use the org.springframework.core.annotation.Order
annotation.
1.10. Application Exit
Each SpringApplication
registers a shutdown hook with the JVM to ensure that the ApplicationContext
closes gracefully on exit.
All the standard Spring lifecycle callbacks (such as the DisposableBean
interface or the @PreDestroy
annotation) can be used.
In addition, beans may implement the org.springframework.boot.ExitCodeGenerator
interface if they wish to return a specific exit code when SpringApplication.exit()
is called.
This exit code can then be passed to System.exit()
to return it as a status code, as shown in the following example:
@SpringBootApplication
public class ExitCodeApplication {
@Bean
public ExitCodeGenerator exitCodeGenerator() {
return () -> 42;
}
public static void main(String[] args) {
System.exit(SpringApplication.exit(SpringApplication.run(ExitCodeApplication.class, args)));
}
}
Also, the ExitCodeGenerator
interface may be implemented by exceptions.
When such an exception is encountered, Spring Boot returns the exit code provided by the implemented getExitCode()
method.
1.11. Admin Features
It is possible to enable admin-related features for the application by specifying the spring.application.admin.enabled
property.
This exposes the SpringApplicationAdminMXBean
on the platform MBeanServer
.
You could use this feature to administer your Spring Boot application remotely.
This feature could also be useful for any service wrapper implementation.
If you want to know on which HTTP port the application is running, get the property with a key of local.server.port .
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2. Externalized Configuration
Spring Boot lets you externalize your configuration so that you can work with the same application code in different environments.
You can use properties files, YAML files, environment variables, and command-line arguments to externalize configuration.
Property values can be injected directly into your beans by using the @Value
annotation, accessed through Spring’s Environment
abstraction, or be bound to structured objects through @ConfigurationProperties
.
Spring Boot uses a very particular PropertySource
order that is designed to allow sensible overriding of values.
Properties are considered in the following order:
-
Devtools global settings properties in the
$HOME/.config/spring-boot
folder when devtools is active. -
@TestPropertySource
annotations on your tests. -
properties
attribute on your tests. Available on@SpringBootTest
and the test annotations for testing a particular slice of your application. -
Command line arguments.
-
Properties from
SPRING_APPLICATION_JSON
(inline JSON embedded in an environment variable or system property). -
ServletConfig
init parameters. -
ServletContext
init parameters. -
JNDI attributes from
java:comp/env
. -
Java System properties (
System.getProperties()
). -
OS environment variables.
-
A
RandomValuePropertySource
that has properties only inrandom.*
. -
Profile-specific application properties outside of your packaged jar (
application-{profile}.properties
and YAML variants). -
Profile-specific application properties packaged inside your jar (
application-{profile}.properties
and YAML variants). -
Application properties outside of your packaged jar (
application.properties
and YAML variants). -
Application properties packaged inside your jar (
application.properties
and YAML variants). -
@PropertySource
annotations on your@Configuration
classes. Please note that such property sources are not added to theEnvironment
until the application context is being refreshed. This is too late to configure certain properties such aslogging.*
andspring.main.*
which are read before refresh begins. -
Default properties (specified by setting
SpringApplication.setDefaultProperties
).
To provide a concrete example, suppose you develop a @Component
that uses a name
property, as shown in the following example:
import org.springframework.stereotype.*;
import org.springframework.beans.factory.annotation.*;
@Component
public class MyBean {
@Value("${name}")
private String name;
// ...
}
On your application classpath (for example, inside your jar) you can have an application.properties
file that provides a sensible default property value for name
.
When running in a new environment, an application.properties
file can be provided outside of your jar that overrides the name
.
For one-off testing, you can launch with a specific command line switch (for example, java -jar app.jar --name="Spring"
).
Spring Boot also supports wildcard locations when loading configuration files.
By default, a wildcard location of config/*/
outside of your jar is supported.
Wildcard locations are also supported when specifying spring.config.additional-location
and spring.config.location
.
Wildcard locations are particularly useful in an environment such as Kubernetes when there are multiple sources of config properties.
For example, if you have some Redis configuration and some MySQL configuration, you might want to keep those two pieces of configuration separate, while requiring that both those are present in an application.properties
that the app can bind to.
This might result in two separate application.properties
files mounted at different locations such as /config/redis/application.properties
and /config/mysql/application.properties
.
In such a case, having a wildcard location of config/*/
, will result in both files being processed.
Locations with wildcards are not processed in a deterministic order and files that match the wildcard cannot be used to override keys in the other. |
The $ SPRING_APPLICATION_JSON='{"acme":{"name":"test"}}' java -jar myapp.jar In the preceding example, you end up with $ java -Dspring.application.json='{"name":"test"}' -jar myapp.jar You can also supply the JSON by using a command line argument, as shown in the following example: $ java -jar myapp.jar --spring.application.json='{"name":"test"}' You can also supply the JSON as a JNDI variable, as follows: |
2.1. Configuring Random Values
The RandomValuePropertySource
is useful for injecting random values (for example, into secrets or test cases).
It can produce integers, longs, uuids, or strings, as shown in the following example:
my.secret=${random.value}
my.number=${random.int}
my.bignumber=${random.long}
my.uuid=${random.uuid}
my.number.less.than.ten=${random.int(10)}
my.number.in.range=${random.int[1024,65536]}
The random.int*
syntax is OPEN value (,max) CLOSE
where the OPEN,CLOSE
are any character and value,max
are integers.
If max
is provided, then value
is the minimum value and max
is the maximum value (exclusive).
2.2. Accessing Command Line Properties
By default, SpringApplication
converts any command line option arguments (that is, arguments starting with --
, such as --server.port=9000
) to a property
and adds them to the Spring Environment
.
As mentioned previously, command line properties always take precedence over other property sources.
If you do not want command line properties to be added to the Environment
, you can disable them by using SpringApplication.setAddCommandLineProperties(false)
.
2.3. Application Property Files
SpringApplication
loads properties from application.properties
files in the following locations and adds them to the Spring Environment
:
-
A
/config
subdirectory of the current directory -
The current directory
-
A classpath
/config
package -
The classpath root
The list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations).
You can also use YAML ('.yml') files as an alternative to '.properties'. |
If you do not like application.properties
as the configuration file name, you can switch to another file name by specifying a spring.config.name
environment property.
You can also refer to an explicit location by using the spring.config.location
environment property (which is a comma-separated list of directory locations or file paths).
The following example shows how to specify a different file name:
$ java -jar myproject.jar --spring.config.name=myproject
The following example shows how to specify two locations:
$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties
spring.config.name and spring.config.location are used very early to determine which files have to be loaded.
They must be defined as an environment property (typically an OS environment variable, a system property, or a command-line argument).
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If spring.config.location
contains directories (as opposed to files), they should end in /
(and, at runtime, be appended with the names generated from spring.config.name
before being loaded, including profile-specific file names).
Files specified in spring.config.location
are used as-is, with no support for profile-specific variants, and are overridden by any profile-specific properties.
Config locations are searched in reverse order.
By default, the configured locations are classpath:/,classpath:/config/,file:./,file:./config/*/,file:./config/
.
The resulting search order is the following:
-
file:./config/
-
file:./config/*/
-
file:./
-
classpath:/config/
-
classpath:/
When custom config locations are configured by using spring.config.location
, they replace the default locations.
For example, if spring.config.location
is configured with the value classpath:/custom-config/,file:./custom-config/
, the search order becomes the following:
-
file:./custom-config/
-
classpath:custom-config/
Alternatively, when custom config locations are configured by using spring.config.additional-location
, they are used in addition to the default locations.
Additional locations are searched before the default locations.
For example, if additional locations of classpath:/custom-config/,file:./custom-config/
are configured, the search order becomes the following:
-
file:./custom-config/
-
classpath:custom-config/
-
file:./config/
-
file:./config/*/
-
file:./
-
classpath:/config/
-
classpath:/
This search ordering lets you specify default values in one configuration file and then selectively override those values in another.
You can provide default values for your application in application.properties
(or whatever other basename you choose with spring.config.name
) in one of the default locations.
These default values can then be overridden at runtime with a different file located in one of the custom locations.
If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (for example, spring.config.name instead of spring.config.name ).
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If your application runs in a container, then JNDI properties (in java:comp/env ) or servlet context initialization parameters can be used instead of, or as well as, environment variables or system properties.
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2.4. Profile-specific Properties
In addition to application.properties
files, profile-specific properties can also be defined by using the following naming convention: application-{profile}.properties
.
The Environment
has a set of default profiles (by default, [default]
) that are used if no active profiles are set.
In other words, if no profiles are explicitly activated, then properties from application-default.properties
are loaded.
Profile-specific properties are loaded from the same locations as standard application.properties
, with profile-specific files always overriding the non-specific ones, whether or not the profile-specific files are inside or outside your packaged jar.
If several profiles are specified, a last-wins strategy applies.
For example, profiles specified by the spring.profiles.active
property are added after those configured through the SpringApplication
API and therefore take precedence.
If you have specified any files in spring.config.location , profile-specific variants of those files are not considered.
Use directories in spring.config.location if you want to also use profile-specific properties.
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2.5. Placeholders in Properties
The values in application.properties
are filtered through the existing Environment
when they are used, so you can refer back to previously defined values (for example, from System properties).
app.name=MyApp
app.description=${app.name} is a Spring Boot application
You can also use this technique to create “short” variants of existing Spring Boot properties. See the howto.html how-to for details. |
2.6. Encrypting Properties
Spring Boot does not provide any built in support for encrypting property values, however, it does provide the hook points necessary to modify values contained in the Spring Environment
.
The EnvironmentPostProcessor
interface allows you to manipulate the Environment
before the application starts.
See howto.html for details.
If you’re looking for a secure way to store credentials and passwords, the Spring Cloud Vault project provides support for storing externalized configuration in HashiCorp Vault.
2.7. Using YAML Instead of Properties
YAML is a superset of JSON and, as such, is a convenient format for specifying hierarchical configuration data.
The SpringApplication
class automatically supports YAML as an alternative to properties whenever you have the SnakeYAML library on your classpath.
If you use “Starters”, SnakeYAML is automatically provided by spring-boot-starter .
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2.7.1. Loading YAML
Spring Framework provides two convenient classes that can be used to load YAML documents.
The YamlPropertiesFactoryBean
loads YAML as Properties
and the YamlMapFactoryBean
loads YAML as a Map
.
For example, consider the following YAML document:
environments:
dev:
url: https://dev.example.com
name: Developer Setup
prod:
url: https://another.example.com
name: My Cool App
The preceding example would be transformed into the following properties:
environments.dev.url=https://dev.example.com
environments.dev.name=Developer Setup
environments.prod.url=https://another.example.com
environments.prod.name=My Cool App
YAML lists are represented as property keys with [index]
dereferencers.
For example, consider the following YAML:
my:
servers:
- dev.example.com
- another.example.com
The preceding example would be transformed into these properties:
my.servers[0]=dev.example.com
my.servers[1]=another.example.com
To bind to properties like that by using Spring Boot’s Binder
utilities (which is what @ConfigurationProperties
does), you need to have a property in the target bean of type java.util.List
(or Set
) and you either need to provide a setter or initialize it with a mutable value.
For example, the following example binds to the properties shown previously:
@ConfigurationProperties(prefix="my")
public class Config {
private List<String> servers = new ArrayList<String>();
public List<String> getServers() {
return this.servers;
}
}
2.7.2. Exposing YAML as Properties in the Spring Environment
The YamlPropertySourceLoader
class can be used to expose YAML as a PropertySource
in the Spring Environment
.
Doing so lets you use the @Value
annotation with placeholders syntax to access YAML properties.
2.7.3. Multi-profile YAML Documents
You can specify multiple profile-specific YAML documents in a single file by using a spring.profiles
key to indicate when the document applies, as shown in the following example:
server:
address: 192.168.1.100
---
spring:
profiles: development
server:
address: 127.0.0.1
---
spring:
profiles: production & eu-central
server:
address: 192.168.1.120
In the preceding example, if the development
profile is active, the server.address
property is 127.0.0.1
.
Similarly, if the production
and eu-central
profiles are active, the server.address
property is 192.168.1.120
.
If the development
, production
and eu-central
profiles are not enabled, then the value for the property is 192.168.1.100
.
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If none are explicitly active when the application context starts, the default profiles are activated.
So, in the following YAML, we set a value for spring.security.user.password
that is available only in the "default" profile:
server:
port: 8000
---
spring:
profiles: default
security:
user:
password: weak
Whereas, in the following example, the password is always set because it is not attached to any profile, and it would have to be explicitly reset in all other profiles as necessary:
server:
port: 8000
spring:
security:
user:
password: weak
Spring profiles designated by using the spring.profiles
element may optionally be negated by using the !
character.
If both negated and non-negated profiles are specified for a single document, at least one non-negated profile must match, and no negated profiles may match.
2.7.4. YAML Shortcomings
YAML files cannot be loaded by using the @PropertySource
annotation.
So, in the case that you need to load values that way, you need to use a properties file.
Using the multi YAML document syntax in profile-specific YAML files can lead to unexpected behavior. For example, consider the following config in a file:
server:
port: 8000
---
spring:
profiles: "!test"
security:
user:
password: "secret"
If you run the application with the argument --spring.profiles.active=dev
you might expect security.user.password
to be set to “secret”, but this is not the case.
The nested document will be filtered because the main file is named application-dev.yml
.
It is already considered to be profile-specific, and nested documents will be ignored.
We recommend that you don’t mix profile-specific YAML files and multiple YAML documents. Stick to using only one of them. |
2.8. Type-safe Configuration Properties
Using the @Value("${property}")
annotation to inject configuration properties can sometimes be cumbersome, especially if you are working with multiple properties or your data is hierarchical in nature.
Spring Boot provides an alternative method of working with properties that lets strongly typed beans govern and validate the configuration of your application.
2.8.1. JavaBean properties binding
It is possible to bind a bean declaring standard JavaBean properties as shown in the following example:
package com.example;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("acme")
public class AcmeProperties {
private boolean enabled;
private InetAddress remoteAddress;
private final Security security = new Security();
public boolean isEnabled() { ... }
public void setEnabled(boolean enabled) { ... }
public InetAddress getRemoteAddress() { ... }
public void setRemoteAddress(InetAddress remoteAddress) { ... }
public Security getSecurity() { ... }
public static class Security {
private String username;
private String password;
private List<String> roles = new ArrayList<>(Collections.singleton("USER"));
public String getUsername() { ... }
public void setUsername(String username) { ... }
public String getPassword() { ... }
public void setPassword(String password) { ... }
public List<String> getRoles() { ... }
public void setRoles(List<String> roles) { ... }
}
}
The preceding POJO defines the following properties:
-
acme.enabled
, with a value offalse
by default. -
acme.remote-address
, with a type that can be coerced fromString
. -
acme.security.username
, with a nested "security" object whose name is determined by the name of the property. In particular, the return type is not used at all there and could have beenSecurityProperties
. -
acme.security.password
. -
acme.security.roles
, with a collection ofString
that defaults toUSER
.
The properties that map to @ConfigurationProperties classes available in Spring Boot, which are configured via properties files, YAML files, environment variables etc., are public API but the accessors (getters/setters) of the class itself are not meant to be used directly.
|
Such arrangement relies on a default empty constructor and getters and setters are usually mandatory, since binding is through standard Java Beans property descriptors, just like in Spring MVC. A setter may be omitted in the following cases:
Some people use Project Lombok to add getters and setters automatically. Make sure that Lombok does not generate any particular constructor for such a type, as it is used automatically by the container to instantiate the object. Finally, only standard Java Bean properties are considered and binding on static properties is not supported. |
2.8.2. Constructor binding
The example in the previous section can be rewritten in an immutable fashion as shown in the following example:
package com.example;
import java.net.InetAddress;
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.ConstructorBinding;
import org.springframework.boot.context.properties.DefaultValue;
@ConstructorBinding
@ConfigurationProperties("acme")
public class AcmeProperties {
private final boolean enabled;
private final InetAddress remoteAddress;
private final Security security;
public AcmeProperties(boolean enabled, InetAddress remoteAddress, Security security) {
this.enabled = enabled;
this.remoteAddress = remoteAddress;
this.security = security;
}
public boolean isEnabled() { ... }
public InetAddress getRemoteAddress() { ... }
public Security getSecurity() { ... }
public static class Security {
private final String username;
private final String password;
private final List<String> roles;
public Security(String username, String password,
@DefaultValue("USER") List<String> roles) {
this.username = username;
this.password = password;
this.roles = roles;
}
public String getUsername() { ... }
public String getPassword() { ... }
public List<String> getRoles() { ... }
}
}
In this setup, the @ConstructorBinding
annotation is used to indicate that constructor binding should be used.
This means that the binder will expect to find a constructor with the parameters that you wish to have bound.
Nested members of a @ConstructorBinding
class (such as Security
in the example above) will also be bound via their constructor.
Default values can be specified using @DefaultValue
and the same conversion service will be applied to coerce the String
value to the target type of a missing property.
To use constructor binding the class must be enabled using @EnableConfigurationProperties or configuration property scanning.
You cannot use constructor binding with beans that are created by the regular Spring mechanisms (e.g. @Component beans, beans created via @Bean methods or beans loaded using @Import )
|
If you have more than one constructor for your class you can also use @ConstructorBinding directly on the constructor that should be bound.
|
2.8.3. Enabling @ConfigurationProperties
-annotated types
Spring Boot provides infrastructure to bind @ConfigurationProperties
types and register them as beans.
You can either enable configuration properties on a class-by-class basis or enable configuration property scanning that works in a similar manner to component scanning.
Sometimes, classes annotated with @ConfigurationProperties
might not be suitable for scanning, for example, if you’re developing your own auto-configuration or you want to enable them conditionally.
In these cases, specify the list of types to process using the @EnableConfigurationProperties
annotation.
This can be done on any @Configuration
class, as shown in the following example:
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(AcmeProperties.class)
public class MyConfiguration {
}
To use configuration property scanning, add the @ConfigurationPropertiesScan
annotation to your application.
Typically, it is added to the main application class that is annotated with @SpringBootApplication
but it can be added to any @Configuration
class.
By default, scanning will occur from the package of the class that declares the annotation.
If you want to define specific packages to scan, you can do so as shown in the following example:
@SpringBootApplication
@ConfigurationPropertiesScan({ "com.example.app", "org.acme.another" })
public class MyApplication {
}
When the The bean name in the example above is |
We recommend that @ConfigurationProperties
only deal with the environment and, in particular, does not inject other beans from the context.
For corner cases, setter injection can be used or any of the *Aware
interfaces provided by the framework (such as EnvironmentAware
if you need access to the Environment
).
If you still want to inject other beans using the constructor, the configuration properties bean must be annotated with @Component
and use JavaBean-based property binding.
2.8.4. Using @ConfigurationProperties
-annotated types
This style of configuration works particularly well with the SpringApplication
external YAML configuration, as shown in the following example:
# application.yml
acme:
remote-address: 192.168.1.1
security:
username: admin
roles:
- USER
- ADMIN
# additional configuration as required
To work with @ConfigurationProperties
beans, you can inject them in the same way as any other bean, as shown in the following example:
@Service
public class MyService {
private final AcmeProperties properties;
@Autowired
public MyService(AcmeProperties properties) {
this.properties = properties;
}
//...
@PostConstruct
public void openConnection() {
Server server = new Server(this.properties.getRemoteAddress());
// ...
}
}
Using @ConfigurationProperties also lets you generate metadata files that can be used by IDEs to offer auto-completion for your own keys.
See the appendix for details.
|
2.8.5. Third-party Configuration
As well as using @ConfigurationProperties
to annotate a class, you can also use it on public @Bean
methods.
Doing so can be particularly useful when you want to bind properties to third-party components that are outside of your control.
To configure a bean from the Environment
properties, add @ConfigurationProperties
to its bean registration, as shown in the following example:
@ConfigurationProperties(prefix = "another")
@Bean
public AnotherComponent anotherComponent() {
...
}
Any JavaBean property defined with the another
prefix is mapped onto that AnotherComponent
bean in manner similar to the preceding AcmeProperties
example.
2.8.6. Relaxed Binding
Spring Boot uses some relaxed rules for binding Environment
properties to @ConfigurationProperties
beans, so there does not need to be an exact match between the Environment
property name and the bean property name.
Common examples where this is useful include dash-separated environment properties (for example, context-path
binds to contextPath
), and capitalized environment properties (for example, PORT
binds to port
).
As an example, consider the following @ConfigurationProperties
class:
@ConfigurationProperties(prefix="acme.my-project.person")
public class OwnerProperties {
private String firstName;
public String getFirstName() {
return this.firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
}
With the preceding code, the following properties names can all be used:
Property | Note |
---|---|
|
Kebab case, which is recommended for use in |
|
Standard camel case syntax. |
|
Underscore notation, which is an alternative format for use in |
|
Upper case format, which is recommended when using system environment variables. |
The prefix value for the annotation must be in kebab case (lowercase and separated by - , such as acme.my-project.person ).
|
Property Source | Simple | List |
---|---|---|
Properties Files |
Camel case, kebab case, or underscore notation |
Standard list syntax using |
YAML Files |
Camel case, kebab case, or underscore notation |
Standard YAML list syntax or comma-separated values |
Environment Variables |
Upper case format with underscore as the delimiter.
|
Numeric values surrounded by underscores, such as |
System properties |
Camel case, kebab case, or underscore notation |
Standard list syntax using |
We recommend that, when possible, properties are stored in lower-case kebab format, such as my.property-name=acme .
|
When binding to Map
properties, if the key
contains anything other than lowercase alpha-numeric characters or -
, you need to use the bracket notation so that the original value is preserved.
If the key is not surrounded by []
, any characters that are not alpha-numeric or -
are removed.
For example, consider binding the following properties to a Map
:
acme:
map:
"[/key1]": value1
"[/key2]": value2
/key3: value3
The properties above will bind to a Map
with /key1
, /key2
and key3
as the keys in the map.
For YAML files, the brackets need to be surrounded by quotes for the keys to be parsed properly. |
2.8.7. Merging Complex Types
When lists are configured in more than one place, overriding works by replacing the entire list.
For example, assume a MyPojo
object with name
and description
attributes that are null
by default.
The following example exposes a list of MyPojo
objects from AcmeProperties
:
@ConfigurationProperties("acme")
public class AcmeProperties {
private final List<MyPojo> list = new ArrayList<>();
public List<MyPojo> getList() {
return this.list;
}
}
Consider the following configuration:
acme:
list:
- name: my name
description: my description
---
spring:
profiles: dev
acme:
list:
- name: my another name
If the dev
profile is not active, AcmeProperties.list
contains one MyPojo
entry, as previously defined.
If the dev
profile is enabled, however, the list
still contains only one entry (with a name of my another name
and a description of null
).
This configuration does not add a second MyPojo
instance to the list, and it does not merge the items.
When a List
is specified in multiple profiles, the one with the highest priority (and only that one) is used.
Consider the following example:
acme:
list:
- name: my name
description: my description
- name: another name
description: another description
---
spring:
profiles: dev
acme:
list:
- name: my another name
In the preceding example, if the dev
profile is active, AcmeProperties.list
contains one MyPojo
entry (with a name of my another name
and a description of null
).
For YAML, both comma-separated lists and YAML lists can be used for completely overriding the contents of the list.
For Map
properties, you can bind with property values drawn from multiple sources.
However, for the same property in multiple sources, the one with the highest priority is used.
The following example exposes a Map<String, MyPojo>
from AcmeProperties
:
@ConfigurationProperties("acme")
public class AcmeProperties {
private final Map<String, MyPojo> map = new HashMap<>();
public Map<String, MyPojo> getMap() {
return this.map;
}
}
Consider the following configuration:
acme:
map:
key1:
name: my name 1
description: my description 1
---
spring:
profiles: dev
acme:
map:
key1:
name: dev name 1
key2:
name: dev name 2
description: dev description 2
If the dev
profile is not active, AcmeProperties.map
contains one entry with key key1
(with a name of my name 1
and a description of my description 1
).
If the dev
profile is enabled, however, map
contains two entries with keys key1
(with a name of dev name 1
and a description of my description 1
) and key2
(with a name of dev name 2
and a description of dev description 2
).
The preceding merging rules apply to properties from all property sources and not just YAML files. |
2.8.8. Properties Conversion
Spring Boot attempts to coerce the external application properties to the right type when it binds to the @ConfigurationProperties
beans.
If you need custom type conversion, you can provide a ConversionService
bean (with a bean named conversionService
) or custom property editors (through a CustomEditorConfigurer
bean) or custom Converters
(with bean definitions annotated as @ConfigurationPropertiesBinding
).
As this bean is requested very early during the application lifecycle, make sure to limit the dependencies that your ConversionService is using.
Typically, any dependency that you require may not be fully initialized at creation time.
You may want to rename your custom ConversionService if it is not required for configuration keys coercion and only rely on custom converters qualified with @ConfigurationPropertiesBinding .
|
Converting durations
Spring Boot has dedicated support for expressing durations.
If you expose a java.time.Duration
property, the following formats in application properties are available:
-
A regular
long
representation (using milliseconds as the default unit unless a@DurationUnit
has been specified) -
The standard ISO-8601 format used by
java.time.Duration
-
A more readable format where the value and the unit are coupled (e.g.
10s
means 10 seconds)
Consider the following example:
@ConfigurationProperties("app.system")
public class AppSystemProperties {
@DurationUnit(ChronoUnit.SECONDS)
private Duration sessionTimeout = Duration.ofSeconds(30);
private Duration readTimeout = Duration.ofMillis(1000);
public Duration getSessionTimeout() {
return this.sessionTimeout;
}
public void setSessionTimeout(Duration sessionTimeout) {
this.sessionTimeout = sessionTimeout;
}
public Duration getReadTimeout() {
return this.readTimeout;
}
public void setReadTimeout(Duration readTimeout) {
this.readTimeout = readTimeout;
}
}
To specify a session timeout of 30 seconds, 30
, PT30S
and 30s
are all equivalent.
A read timeout of 500ms can be specified in any of the following form: 500
, PT0.5S
and 500ms
.
You can also use any of the supported units. These are:
-
ns
for nanoseconds -
us
for microseconds -
ms
for milliseconds -
s
for seconds -
m
for minutes -
h
for hours -
d
for days
The default unit is milliseconds and can be overridden using @DurationUnit
as illustrated in the sample above.
If you are upgrading from a previous version that is simply using Long to express the duration, make sure to define the unit (using @DurationUnit ) if it isn’t milliseconds alongside the switch to Duration .
Doing so gives a transparent upgrade path while supporting a much richer format.
|
Converting Data Sizes
Spring Framework has a DataSize
value type that expresses a size in bytes.
If you expose a DataSize
property, the following formats in application properties are available:
-
A regular
long
representation (using bytes as the default unit unless a@DataSizeUnit
has been specified) -
A more readable format where the value and the unit are coupled (e.g.
10MB
means 10 megabytes)
Consider the following example:
@ConfigurationProperties("app.io")
public class AppIoProperties {
@DataSizeUnit(DataUnit.MEGABYTES)
private DataSize bufferSize = DataSize.ofMegabytes(2);
private DataSize sizeThreshold = DataSize.ofBytes(512);
public DataSize getBufferSize() {
return this.bufferSize;
}
public void setBufferSize(DataSize bufferSize) {
this.bufferSize = bufferSize;
}
public DataSize getSizeThreshold() {
return this.sizeThreshold;
}
public void setSizeThreshold(DataSize sizeThreshold) {
this.sizeThreshold = sizeThreshold;
}
}
To specify a buffer size of 10 megabytes, 10
and 10MB
are equivalent.
A size threshold of 256 bytes can be specified as 256
or 256B
.
You can also use any of the supported units. These are:
-
B
for bytes -
KB
for kilobytes -
MB
for megabytes -
GB
for gigabytes -
TB
for terabytes
The default unit is bytes and can be overridden using @DataSizeUnit
as illustrated in the sample above.
If you are upgrading from a previous version that is simply using Long to express the size, make sure to define the unit (using @DataSizeUnit ) if it isn’t bytes alongsidethe switch to DataSize .
Doing so gives a transparent upgrade path while supporting a much richer format.
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2.8.9. @ConfigurationProperties Validation
Spring Boot attempts to validate @ConfigurationProperties
classes whenever they are annotated with Spring’s @Validated
annotation.
You can use JSR-303 javax.validation
constraint annotations directly on your configuration class.
To do so, ensure that a compliant JSR-303 implementation is on your classpath and then add constraint annotations to your fields, as shown in the following example:
@ConfigurationProperties(prefix="acme")
@Validated
public class AcmeProperties {
@NotNull
private InetAddress remoteAddress;
// ... getters and setters
}
You can also trigger validation by annotating the @Bean method that creates the configuration properties with @Validated .
|
To ensure that validation is always triggered for nested properties, even when no properties are found, the associated field must be annotated with @Valid
.
The following example builds on the preceding AcmeProperties
example:
@ConfigurationProperties(prefix="acme")
@Validated
public class AcmeProperties {
@NotNull
private InetAddress remoteAddress;
@Valid
private final Security security = new Security();
// ... getters and setters
public static class Security {
@NotEmpty
public String username;
// ... getters and setters
}
}
You can also add a custom Spring Validator
by creating a bean definition called configurationPropertiesValidator
.
The @Bean
method should be declared static
.
The configuration properties validator is created very early in the application’s lifecycle, and declaring the @Bean
method as static lets the bean be created without having to instantiate the @Configuration
class.
Doing so avoids any problems that may be caused by early instantiation.
The spring-boot-actuator module includes an endpoint that exposes all @ConfigurationProperties beans.
Point your web browser to /actuator/configprops or use the equivalent JMX endpoint.
See the "Production ready features" section for details.
|
2.8.10. @ConfigurationProperties vs. @Value
The @Value
annotation is a core container feature, and it does not provide the same features as type-safe configuration properties.
The following table summarizes the features that are supported by @ConfigurationProperties
and @Value
:
Feature | @ConfigurationProperties |
@Value |
---|---|---|
Yes |
No |
|
Yes |
No |
|
|
No |
Yes |
If you define a set of configuration keys for your own components, we recommend you group them in a POJO annotated with @ConfigurationProperties
.
You should also be aware that, since @Value
does not support relaxed binding, it is not a good candidate if you need to provide the value by using environment variables.
Finally, while you can write a SpEL
expression in @Value
, such expressions are not processed from application property files.
3. Profiles
Spring Profiles provide a way to segregate parts of your application configuration and make it be available only in certain environments.
Any @Component
, @Configuration
or @ConfigurationProperties
can be marked with @Profile
to limit when it is loaded, as shown in the following example:
@Configuration(proxyBeanMethods = false)
@Profile("production")
public class ProductionConfiguration {
// ...
}
If @ConfigurationProperties beans are registered via @EnableConfigurationProperties instead of automatic scanning, the @Profile annotation needs to be specified on the @Configuration class that has the @EnableConfigurationProperties annotation.
In the case where @ConfigurationProperties are scanned, @Profile can be specified on the @ConfigurationProperties class itself.
|
You can use a spring.profiles.active
Environment
property to specify which profiles are active.
You can specify the property in any of the ways described earlier in this chapter.
For example, you could include it in your application.properties
, as shown in the following example:
spring.profiles.active=dev,hsqldb
You could also specify it on the command line by using the following switch: --spring.profiles.active=dev,hsqldb
.
3.1. Adding Active Profiles
The spring.profiles.active
property follows the same ordering rules as other properties: The highest PropertySource
wins.
This means that you can specify active profiles in application.properties
and then replace them by using the command line switch.
Sometimes, it is useful to have profil-specific properties that add to the active profiles rather than replace them.
The spring.profiles.include
property can be used to unconditionally add active profiles.
The SpringApplication
entry point also has a Java API for setting additional profiles (that is, on top of those activated by the spring.profiles.active
property).
See the setAdditionalProfiles()
method in SpringApplication.
For example, when an application with the following properties is run by using the switch, --spring.profiles.active=prod
, the proddb
and prodmq
profiles are also activated:
---
my.property: fromyamlfile
---
spring.profiles: prod
spring.profiles.include:
- proddb
- prodmq
Remember that the spring.profiles property can be defined in a YAML document to determine when this particular document is included in the configuration.
See howto.html for more details.
|
3.2. Programmatically Setting Profiles
You can programmatically set active profiles by calling SpringApplication.setAdditionalProfiles(…)
before your application runs.
It is also possible to activate profiles by using Spring’s ConfigurableEnvironment
interface.
3.3. Profile-specific Configuration Files
Profile-specific variants of both application.properties
(or application.yml
) and files referenced through @ConfigurationProperties
are considered as files and loaded.
See "Profile-specific Properties" for details.
4. Logging
Spring Boot uses Commons Logging for all internal logging but leaves the underlying log implementation open. Default configurations are provided for Java Util Logging, Log4J2, and Logback. In each case, loggers are pre-configured to use console output with optional file output also available.
By default, if you use the “Starters”, Logback is used for logging. Appropriate Logback routing is also included to ensure that dependent libraries that use Java Util Logging, Commons Logging, Log4J, or SLF4J all work correctly.
There are a lot of logging frameworks available for Java. Do not worry if the above list seems confusing. Generally, you do not need to change your logging dependencies and the Spring Boot defaults work just fine. |
When you deploy your application to a servlet container or application server, logging performed via the Java Util Logging API is not routed into your application’s logs. This prevents logging performed by the container or other applications that have been deployed to it from appearing in your application’s logs. |
4.1. Log Format
The default log output from Spring Boot resembles the following example:
2019-03-05 10:57:51.112 INFO 45469 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/7.0.52 2019-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2019-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1358 ms 2019-03-05 10:57:51.698 INFO 45469 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/] 2019-03-05 10:57:51.702 INFO 45469 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
The following items are output:
-
Date and Time: Millisecond precision and easily sortable.
-
Log Level:
ERROR
,WARN
,INFO
,DEBUG
, orTRACE
. -
Process ID.
-
A
---
separator to distinguish the start of actual log messages. -
Thread name: Enclosed in square brackets (may be truncated for console output).
-
Logger name: This is usually the source class name (often abbreviated).
-
The log message.
Logback does not have a FATAL level.
It is mapped to ERROR .
|
4.2. Console Output
The default log configuration echoes messages to the console as they are written.
By default, ERROR
-level, WARN
-level, and INFO
-level messages are logged.
You can also enable a “debug” mode by starting your application with a --debug
flag.
$ java -jar myapp.jar --debug
You can also specify debug=true in your application.properties .
|
When the debug mode is enabled, a selection of core loggers (embedded container, Hibernate, and Spring Boot) are configured to output more information.
Enabling the debug mode does not configure your application to log all messages with DEBUG
level.
Alternatively, you can enable a “trace” mode by starting your application with a --trace
flag (or trace=true
in your application.properties
).
Doing so enables trace logging for a selection of core loggers (embedded container, Hibernate schema generation, and the whole Spring portfolio).
4.2.1. Color-coded Output
If your terminal supports ANSI, color output is used to aid readability.
You can set spring.output.ansi.enabled
to a supported value to override the auto-detection.
Color coding is configured by using the %clr
conversion word.
In its simplest form, the converter colors the output according to the log level, as shown in the following example:
%clr(%5p)
The following table describes the mapping of log levels to colors:
Level | Color |
---|---|
|
Red |
|
Red |
|
Yellow |
|
Green |
|
Green |
|
Green |
Alternatively, you can specify the color or style that should be used by providing it as an option to the conversion. For example, to make the text yellow, use the following setting:
%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){yellow}
The following colors and styles are supported:
-
blue
-
cyan
-
faint
-
green
-
magenta
-
red
-
yellow
4.3. File Output
By default, Spring Boot logs only to the console and does not write log files.
If you want to write log files in addition to the console output, you need to set a logging.file.name
or logging.file.path
property (for example, in your application.properties
).
The following table shows how the logging.*
properties can be used together:
logging.file.name |
logging.file.path |
Example | Description |
---|---|---|---|
(none) |
(none) |
Console only logging. |
|
Specific file |
(none) |
|
Writes to the specified log file. Names can be an exact location or relative to the current directory. |
(none) |
Specific directory |
|
Writes |
Log files rotate when they reach 10 MB and, as with console output, ERROR
-level, WARN
-level, and INFO
-level messages are logged by default.
Size limits can be changed using the logging.file.max-size
property.
Rotated log files of the last 7 days are kept by default unless the logging.file.max-history
property has been set.
The total size of log archives can be capped using logging.file.total-size-cap
.
When the total size of log archives exceeds that threshold, backups will be deleted.
To force log archive cleanup on application startup, use the logging.file.clean-history-on-start
property.
Logging properties are independent of the actual logging infrastructure.
As a result, specific configuration keys (such as logback.configurationFile for Logback) are not managed by spring Boot.
|
4.4. Log Levels
All the supported logging systems can have the logger levels set in the Spring Environment
(for example, in application.properties
) by using logging.level.<logger-name>=<level>
where level
is one of TRACE, DEBUG, INFO, WARN, ERROR, FATAL, or OFF.
The root
logger can be configured by using logging.level.root
.
The following example shows potential logging settings in application.properties
:
logging.level.root=warn
logging.level.org.springframework.web=debug
logging.level.org.hibernate=error
It’s also possible to set logging levels using environment variables.
For example, LOGGING_LEVEL_ORG_SPRINGFRAMEWORK_WEB=DEBUG
will set org.springframework.web
to DEBUG
.
The above approach will only work for package level logging.
Since relaxed binding always converts environment variables to lowercase, it’s not possible to configure logging for an individual class in this way.
If you need to configure logging for a class, you can use the SPRING_APPLICATION_JSON variable.
|
4.5. Log Groups
It’s often useful to be able to group related loggers together so that they can all be configured at the same time. For example, you might commonly change the logging levels for all Tomcat related loggers, but you can’t easily remember top level packages.
To help with this, Spring Boot allows you to define logging groups in your Spring Environment
.
For example, here’s how you could define a “tomcat” group by adding it to your application.properties
:
logging.group.tomcat=org.apache.catalina, org.apache.coyote, org.apache.tomcat
Once defined, you can change the level for all the loggers in the group with a single line:
logging.level.tomcat=TRACE
Spring Boot includes the following pre-defined logging groups that can be used out-of-the-box:
Name | Loggers |
---|---|
web |
|
sql |
|
4.6. Custom Log Configuration
The various logging systems can be activated by including the appropriate libraries on the classpath and can be further customized by providing a suitable configuration file in the root of the classpath or in a location specified by the following Spring Environment
property: logging.config
.
You can force Spring Boot to use a particular logging system by using the org.springframework.boot.logging.LoggingSystem
system property.
The value should be the fully qualified class name of a LoggingSystem
implementation.
You can also disable Spring Boot’s logging configuration entirely by using a value of none
.
Since logging is initialized before the ApplicationContext is created, it is not possible to control logging from @PropertySources in Spring @Configuration files.
The only way to change the logging system or disable it entirely is via System properties.
|
Depending on your logging system, the following files are loaded:
Logging System | Customization |
---|---|
Logback |
|
Log4j2 |
|
JDK (Java Util Logging) |
|
When possible, we recommend that you use the -spring variants for your logging configuration (for example, logback-spring.xml rather than logback.xml ).
If you use standard configuration locations, Spring cannot completely control log initialization.
|
There are known classloading issues with Java Util Logging that cause problems when running from an 'executable jar'. We recommend that you avoid it when running from an 'executable jar' if at all possible. |
To help with the customization, some other properties are transferred from the Spring Environment
to System properties, as described in the following table:
Spring Environment | System Property | Comments |
---|---|---|
|
|
The conversion word used when logging exceptions. |
|
|
Whether to clean the archive log files on startup (if LOG_FILE enabled). (Only supported with the default Logback setup.) |
|
|
If defined, it is used in the default log configuration. |
|
|
Maximum log file size (if LOG_FILE enabled). (Only supported with the default Logback setup.) |
|
|
Maximum number of archive log files to keep (if LOG_FILE enabled). (Only supported with the default Logback setup.) |
|
|
If defined, it is used in the default log configuration. |
|
|
Total size of log backups to be kept (if LOG_FILE enabled). (Only supported with the default Logback setup.) |
|
|
The log pattern to use on the console (stdout). (Only supported with the default Logback setup.) |
|
|
Appender pattern for log date format. (Only supported with the default Logback setup.) |
|
|
The log pattern to use in a file (if |
|
|
The format to use when rendering the log level (default |
|
|
Pattern for rolled-over log file names (default |
|
|
The current process ID (discovered if possible and when not already defined as an OS environment variable). |
All the supported logging systems can consult System properties when parsing their configuration files.
See the default configurations in spring-boot.jar
for examples:
If you want to use a placeholder in a logging property, you should use Spring Boot’s syntax and not the syntax of the underlying framework.
Notably, if you use Logback, you should use |
You can add MDC and other ad-hoc content to log lines by overriding only the 2019-08-30 12:30:04.031 user:someone INFO 22174 --- [ nio-8080-exec-0] demo.Controller Handling authenticated request |
4.7. Logback Extensions
Spring Boot includes a number of extensions to Logback that can help with advanced configuration.
You can use these extensions in your logback-spring.xml
configuration file.
Because the standard logback.xml configuration file is loaded too early, you cannot use extensions in it.
You need to either use logback-spring.xml or define a logging.config property.
|
The extensions cannot be used with Logback’s configuration scanning. If you attempt to do so, making changes to the configuration file results in an error similar to one of the following being logged: |
ERROR in ch.qos.logback.core.joran.spi.Interpreter@4:71 - no applicable action for [springProperty], current ElementPath is [[configuration][springProperty]] ERROR in ch.qos.logback.core.joran.spi.Interpreter@4:71 - no applicable action for [springProfile], current ElementPath is [[configuration][springProfile]]
4.7.1. Profile-specific Configuration
The <springProfile>
tag lets you optionally include or exclude sections of configuration based on the active Spring profiles.
Profile sections are supported anywhere within the <configuration>
element.
Use the name
attribute to specify which profile accepts the configuration.
The <springProfile>
tag can contain a simple profile name (for example staging
) or a profile expression.
A profile expression allows for more complicated profile logic to be expressed, for example production & (eu-central | eu-west)
.
Check the reference guide for more details.
The following listing shows three sample profiles:
<springProfile name="staging">
<!-- configuration to be enabled when the "staging" profile is active -->
</springProfile>
<springProfile name="dev | staging">
<!-- configuration to be enabled when the "dev" or "staging" profiles are active -->
</springProfile>
<springProfile name="!production">
<!-- configuration to be enabled when the "production" profile is not active -->
</springProfile>
4.7.2. Environment Properties
The <springProperty>
tag lets you expose properties from the Spring Environment
for use within Logback.
Doing so can be useful if you want to access values from your application.properties
file in your Logback configuration.
The tag works in a similar way to Logback’s standard <property>
tag.
However, rather than specifying a direct value
, you specify the source
of the property (from the Environment
).
If you need to store the property somewhere other than in local
scope, you can use the scope
attribute.
If you need a fallback value (in case the property is not set in the Environment
), you can use the defaultValue
attribute.
The following example shows how to expose properties for use within Logback:
<springProperty scope="context" name="fluentHost" source="myapp.fluentd.host"
defaultValue="localhost"/>
<appender name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender">
<remoteHost>${fluentHost}</remoteHost>
...
</appender>
The source must be specified in kebab case (such as my.property-name ).
However, properties can be added to the Environment by using the relaxed rules.
|
5. Internationalization
Spring Boot supports localized messages so that your application can cater to users of different language preferences.
By default, Spring Boot looks for the presence of a messages
resource bundle at the root of the classpath.
The auto-configuration applies when the default properties file for the configured resource bundle is available (i.e. messages.properties by default).
If your resource bundle contains only language-specific properties files, you are required to add the default.
If no properties file is found that matches any of the configured base names, there will be no auto-configured MessageSource .
|
The basename of the resource bundle as well as several other attributes can be configured using the spring.messages
namespace, as shown in the following example:
spring.messages.basename=messages,config.i18n.messages
spring.messages.fallback-to-system-locale=false
spring.messages.basename supports comma-separated list of locations, either a package qualifier or a resource resolved from the classpath root.
|
See MessageSourceProperties
for more supported options.
6. JSON
Spring Boot provides integration with three JSON mapping libraries:
-
Gson
-
Jackson
-
JSON-B
Jackson is the preferred and default library.
6.1. Jackson
Auto-configuration for Jackson is provided and Jackson is part of spring-boot-starter-json
.
When Jackson is on the classpath an ObjectMapper
bean is automatically configured.
Several configuration properties are provided for customizing the configuration of the ObjectMapper
.
7. Developing Web Applications
Spring Boot is well suited for web application development.
You can create a self-contained HTTP server by using embedded Tomcat, Jetty, Undertow, or Netty.
Most web applications use the spring-boot-starter-web
module to get up and running quickly.
You can also choose to build reactive web applications by using the spring-boot-starter-webflux
module.
If you have not yet developed a Spring Boot web application, you can follow the "Hello World!" example in the Getting started section.
7.1. The “Spring Web MVC Framework”
The Spring Web MVC framework (often referred to as simply “Spring MVC”) is a rich “model view controller” web framework.
Spring MVC lets you create special @Controller
or @RestController
beans to handle incoming HTTP requests.
Methods in your controller are mapped to HTTP by using @RequestMapping
annotations.
The following code shows a typical @RestController
that serves JSON data:
@RestController
@RequestMapping(value="/users")
public class MyRestController {
@RequestMapping(value="/{user}", method=RequestMethod.GET)
public User getUser(@PathVariable Long user) {
// ...
}
@RequestMapping(value="/{user}/customers", method=RequestMethod.GET)
List<Customer> getUserCustomers(@PathVariable Long user) {
// ...
}
@RequestMapping(value="/{user}", method=RequestMethod.DELETE)
public User deleteUser(@PathVariable Long user) {
// ...
}
}
Spring MVC is part of the core Spring Framework, and detailed information is available in the reference documentation. There are also several guides that cover Spring MVC available at spring.io/guides.
7.1.1. Spring MVC Auto-configuration
Spring Boot provides auto-configuration for Spring MVC that works well with most applications.
The auto-configuration adds the following features on top of Spring’s defaults:
-
Inclusion of
ContentNegotiatingViewResolver
andBeanNameViewResolver
beans. -
Support for serving static resources, including support for WebJars (covered later in this document)).
-
Automatic registration of
Converter
,GenericConverter
, andFormatter
beans. -
Support for
HttpMessageConverters
(covered later in this document). -
Automatic registration of
MessageCodesResolver
(covered later in this document). -
Static
index.html
support. -
Custom
Favicon
support (covered later in this document). -
Automatic use of a
ConfigurableWebBindingInitializer
bean (covered later in this document).
If you want to keep those Spring Boot MVC customizations and make more MVC customizations (interceptors, formatters, view controllers, and other features), you can add your own @Configuration
class of type WebMvcConfigurer
but without @EnableWebMvc
.
If you want to provide custom instances of RequestMappingHandlerMapping
, RequestMappingHandlerAdapter
, or ExceptionHandlerExceptionResolver
, and still keep the Spring Boot MVC customizations, you can declare a bean of type WebMvcRegistrations
and use it to provide custom instances of those components.
If you want to take complete control of Spring MVC, you can add your own @Configuration
annotated with @EnableWebMvc
, or alternatively add your own @Configuration
-annotated DelegatingWebMvcConfiguration
as described in the Javadoc of @EnableWebMvc
.
7.1.2. HttpMessageConverters
Spring MVC uses the HttpMessageConverter
interface to convert HTTP requests and responses.
Sensible defaults are included out of the box.
For example, objects can be automatically converted to JSON (by using the Jackson library) or XML (by using the Jackson XML extension, if available, or by using JAXB if the Jackson XML extension is not available).
By default, strings are encoded in UTF-8
.
If you need to add or customize converters, you can use Spring Boot’s HttpMessageConverters
class, as shown in the following listing:
import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
import org.springframework.context.annotation.*;
import org.springframework.http.converter.*;
@Configuration(proxyBeanMethods = false)
public class MyConfiguration {
@Bean
public HttpMessageConverters customConverters() {
HttpMessageConverter<?> additional = ...
HttpMessageConverter<?> another = ...
return new HttpMessageConverters(additional, another);
}
}
Any HttpMessageConverter
bean that is present in the context is added to the list of converters.
You can also override default converters in the same way.
7.1.3. Custom JSON Serializers and Deserializers
If you use Jackson to serialize and deserialize JSON data, you might want to write your own JsonSerializer
and JsonDeserializer
classes.
Custom serializers are usually registered with Jackson through a module, but Spring Boot provides an alternative @JsonComponent
annotation that makes it easier to directly register Spring Beans.
You can use the @JsonComponent
annotation directly on JsonSerializer
, JsonDeserializer
or KeyDeserializer
implementations.
You can also use it on classes that contain serializers/deserializers as inner classes, as shown in the following example:
import java.io.*;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;
import org.springframework.boot.jackson.*;
@JsonComponent
public class Example {
public static class Serializer extends JsonSerializer<SomeObject> {
// ...
}
public static class Deserializer extends JsonDeserializer<SomeObject> {
// ...
}
}
All @JsonComponent
beans in the ApplicationContext
are automatically registered with Jackson.
Because @JsonComponent
is meta-annotated with @Component
, the usual component-scanning rules apply.
Spring Boot also provides JsonObjectSerializer
and JsonObjectDeserializer
base classes that provide useful alternatives to the standard Jackson versions when serializing objects.
See JsonObjectSerializer
and JsonObjectDeserializer
in the Javadoc for details.
7.1.4. MessageCodesResolver
Spring MVC has a strategy for generating error codes for rendering error messages from binding errors: MessageCodesResolver
.
If you set the spring.mvc.message-codes-resolver-format
property PREFIX_ERROR_CODE
or POSTFIX_ERROR_CODE
, Spring Boot creates one for you (see the enumeration in DefaultMessageCodesResolver.Format
).
7.1.5. Static Content
By default, Spring Boot serves static content from a directory called /static
(or /public
or /resources
or /META-INF/resources
) in the classpath or from the root of the ServletContext
.
It uses the ResourceHttpRequestHandler
from Spring MVC so that you can modify that behavior by adding your own WebMvcConfigurer
and overriding the addResourceHandlers
method.
In a stand-alone web application, the default servlet from the container is also enabled and acts as a fallback, serving content from the root of the ServletContext
if Spring decides not to handle it.
Most of the time, this does not happen (unless you modify the default MVC configuration), because Spring can always handle requests through the DispatcherServlet
.
By default, resources are mapped on /**
, but you can tune that with the spring.mvc.static-path-pattern
property.
For instance, relocating all resources to /resources/**
can be achieved as follows:
spring.mvc.static-path-pattern=/resources/**
You can also customize the static resource locations by using the spring.resources.static-locations
property (replacing the default values with a list of directory locations).
The root Servlet context path, "/"
, is automatically added as a location as well.
In addition to the “standard” static resource locations mentioned earlier, a special case is made for Webjars content.
Any resources with a path in /webjars/**
are served from jar files if they are packaged in the Webjars format.
Do not use the src/main/webapp directory if your application is packaged as a jar.
Although this directory is a common standard, it works only with war packaging, and it is silently ignored by most build tools if you generate a jar.
|
Spring Boot also supports the advanced resource handling features provided by Spring MVC, allowing use cases such as cache-busting static resources or using version agnostic URLs for Webjars.
To use version agnostic URLs for Webjars, add the webjars-locator-core
dependency.
Then declare your Webjar.
Using jQuery as an example, adding "/webjars/jquery/jquery.min.js"
results in "/webjars/jquery/x.y.z/jquery.min.js"
where x.y.z
is the Webjar version.
If you use JBoss, you need to declare the webjars-locator-jboss-vfs dependency instead of the webjars-locator-core .
Otherwise, all Webjars resolve as a 404 .
|
To use cache busting, the following configuration configures a cache busting solution for all static resources, effectively adding a content hash, such as <link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/>
, in URLs:
spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**
Links to resources are rewritten in templates at runtime, thanks to a ResourceUrlEncodingFilter that is auto-configured for Thymeleaf and FreeMarker.
You should manually declare this filter when using JSPs.
Other template engines are currently not automatically supported but can be with custom template macros/helpers and the use of the ResourceUrlProvider .
|
When loading resources dynamically with, for example, a JavaScript module loader, renaming files is not an option. That is why other strategies are also supported and can be combined. A "fixed" strategy adds a static version string in the URL without changing the file name, as shown in the following example:
spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**
spring.resources.chain.strategy.fixed.enabled=true
spring.resources.chain.strategy.fixed.paths=/js/lib/
spring.resources.chain.strategy.fixed.version=v12
With this configuration, JavaScript modules located under "/js/lib/"
use a fixed versioning strategy ("/v12/js/lib/mymodule.js"
), while other resources still use the content one (<link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/>
).
See ResourceProperties
for more supported options.
This feature has been thoroughly described in a dedicated blog post and in Spring Framework’s reference documentation. |
7.1.6. Welcome Page
Spring Boot supports both static and templated welcome pages.
It first looks for an index.html
file in the configured static content locations.
If one is not found, it then looks for an index
template.
If either is found, it is automatically used as the welcome page of the application.
7.1.7. Custom Favicon
As with other static resources, Spring Boot looks for a favicon.ico
in the configured static content locations.
If such a file is present, it is automatically used as the favicon of the application.
7.1.8. Path Matching and Content Negotiation
Spring MVC can map incoming HTTP requests to handlers by looking at the request path and matching it to the mappings defined in your application (for example, @GetMapping
annotations on Controller methods).
Spring Boot chooses to disable suffix pattern matching by default, which means that requests like "GET /projects/spring-boot.json"
won’t be matched to @GetMapping("/projects/spring-boot")
mappings.
This is considered as a best practice for Spring MVC applications.
This feature was mainly useful in the past for HTTP clients which did not send proper "Accept" request headers; we needed to make sure to send the correct Content Type to the client.
Nowadays, Content Negotiation is much more reliable.
There are other ways to deal with HTTP clients that don’t consistently send proper "Accept" request headers.
Instead of using suffix matching, we can use a query parameter to ensure that requests like "GET /projects/spring-boot?format=json"
will be mapped to @GetMapping("/projects/spring-boot")
:
spring.mvc.contentnegotiation.favor-parameter=true
# We can change the parameter name, which is "format" by default:
# spring.mvc.contentnegotiation.parameter-name=myparam
# We can also register additional file extensions/media types with:
spring.mvc.contentnegotiation.media-types.markdown=text/markdown
If you understand the caveats and would still like your application to use suffix pattern matching, the following configuration is required:
spring.mvc.contentnegotiation.favor-path-extension=true
spring.mvc.pathmatch.use-suffix-pattern=true
Alternatively, rather than open all suffix patterns, it’s more secure to just support registered suffix patterns:
spring.mvc.contentnegotiation.favor-path-extension=true
spring.mvc.pathmatch.use-registered-suffix-pattern=true
# You can also register additional file extensions/media types with:
# spring.mvc.contentnegotiation.media-types.adoc=text/asciidoc
7.1.9. ConfigurableWebBindingInitializer
Spring MVC uses a WebBindingInitializer
to initialize a WebDataBinder
for a particular request.
If you create your own ConfigurableWebBindingInitializer
@Bean
, Spring Boot automatically configures Spring MVC to use it.
7.1.10. Template Engines
As well as REST web services, you can also use Spring MVC to serve dynamic HTML content. Spring MVC supports a variety of templating technologies, including Thymeleaf, FreeMarker, and JSPs. Also, many other templating engines include their own Spring MVC integrations.
Spring Boot includes auto-configuration support for the following templating engines:
If possible, JSPs should be avoided. There are several known limitations when using them with embedded servlet containers. |
When you use one of these templating engines with the default configuration, your templates are picked up automatically from src/main/resources/templates
.
Depending on how you run your application, IntelliJ IDEA orders the classpath differently.
Running your application in the IDE from its main method results in a different ordering than when you run your application by using Maven or Gradle or from its packaged jar.
This can cause Spring Boot to fail to find the templates on the classpath.
If you have this problem, you can reorder the classpath in the IDE to place the module’s classes and resources first.
Alternatively, you can configure the template prefix to search every templates directory on the classpath, as follows: classpath*:/templates/ .
|
7.1.11. Error Handling
By default, Spring Boot provides an /error
mapping that handles all errors in a sensible way, and it is registered as a “global” error page in the servlet container.
For machine clients, it produces a JSON response with details of the error, the HTTP status, and the exception message.
For browser clients, there is a “whitelabel” error view that renders the same data in HTML format (to customize it, add a View
that resolves to error
).
To replace the default behavior completely, you can implement ErrorController
and register a bean definition of that type or add a bean of type ErrorAttributes
to use the existing mechanism but replace the contents.
The BasicErrorController can be used as a base class for a custom ErrorController .
This is particularly useful if you want to add a handler for a new content type (the default is to handle text/html specifically and provide a fallback for everything else).
To do so, extend BasicErrorController , add a public method with a @RequestMapping that has a produces attribute, and create a bean of your new type.
|
You can also define a class annotated with @ControllerAdvice
to customize the JSON document to return for a particular controller and/or exception type, as shown in the following example:
@ControllerAdvice(basePackageClasses = AcmeController.class)
public class AcmeControllerAdvice extends ResponseEntityExceptionHandler {
@ExceptionHandler(YourException.class)
@ResponseBody
ResponseEntity<?> handleControllerException(HttpServletRequest request, Throwable ex) {
HttpStatus status = getStatus(request);
return new ResponseEntity<>(new CustomErrorType(status.value(), ex.getMessage()), status);
}
private HttpStatus getStatus(HttpServletRequest request) {
Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
if (statusCode == null) {
return HttpStatus.INTERNAL_SERVER_ERROR;
}
return HttpStatus.valueOf(statusCode);
}
}
In the preceding example, if YourException
is thrown by a controller defined in the same package as AcmeController
, a JSON representation of the CustomErrorType
POJO is used instead of the ErrorAttributes
representation.
Custom Error Pages
If you want to display a custom HTML error page for a given status code, you can add a file to an /error
folder.
Error pages can either be static HTML (that is, added under any of the static resource folders) or be built by using templates.
The name of the file should be the exact status code or a series mask.
For example, to map 404
to a static HTML file, your folder structure would be as follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- public/
+- error/
| +- 404.html
+- <other public assets>
To map all 5xx
errors by using a FreeMarker template, your folder structure would be as follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- templates/
+- error/
| +- 5xx.ftlh
+- <other templates>
For more complex mappings, you can also add beans that implement the ErrorViewResolver
interface, as shown in the following example:
public class MyErrorViewResolver implements ErrorViewResolver {
@Override
public ModelAndView resolveErrorView(HttpServletRequest request,
HttpStatus status, Map<String, Object> model) {
// Use the request or status to optionally return a ModelAndView
return ...
}
}
You can also use regular Spring MVC features such as @ExceptionHandler
methods and @ControllerAdvice
.
The ErrorController
then picks up any unhandled exceptions.
Mapping Error Pages outside of Spring MVC
For applications that do not use Spring MVC, you can use the ErrorPageRegistrar
interface to directly register ErrorPages
.
This abstraction works directly with the underlying embedded servlet container and works even if you do not have a Spring MVC DispatcherServlet
.
@Bean
public ErrorPageRegistrar errorPageRegistrar(){
return new MyErrorPageRegistrar();
}
// ...
private static class MyErrorPageRegistrar implements ErrorPageRegistrar {
@Override
public void registerErrorPages(ErrorPageRegistry registry) {
registry.addErrorPages(new ErrorPage(HttpStatus.BAD_REQUEST, "/400"));
}
}
If you register an ErrorPage with a path that ends up being handled by a Filter (as is common with some non-Spring web frameworks, like Jersey and Wicket), then the Filter has to be explicitly registered as an ERROR dispatcher, as shown in the following example:
|
@Bean
public FilterRegistrationBean myFilter() {
FilterRegistrationBean registration = new FilterRegistrationBean();
registration.setFilter(new MyFilter());
...
registration.setDispatcherTypes(EnumSet.allOf(DispatcherType.class));
return registration;
}
Note that the default FilterRegistrationBean
does not include the ERROR
dispatcher type.
CAUTION:When deployed to a servlet container, Spring Boot uses its error page filter to forward a request with an error status to the appropriate error page.
The request can only be forwarded to the correct error page if the response has not already been committed.
By default, WebSphere Application Server 8.0 and later commits the response upon successful completion of a servlet’s service method.
You should disable this behavior by setting com.ibm.ws.webcontainer.invokeFlushAfterService
to false
.
7.1.12. Spring HATEOAS
If you develop a RESTful API that makes use of hypermedia, Spring Boot provides auto-configuration for Spring HATEOAS that works well with most applications.
The auto-configuration replaces the need to use @EnableHypermediaSupport
and registers a number of beans to ease building hypermedia-based applications, including a LinkDiscoverers
(for client side support) and an ObjectMapper
configured to correctly marshal responses into the desired representation.
The ObjectMapper
is customized by setting the various spring.jackson.*
properties or, if one exists, by a Jackson2ObjectMapperBuilder
bean.
You can take control of Spring HATEOAS’s configuration by using @EnableHypermediaSupport
.
Note that doing so disables the ObjectMapper
customization described earlier.
7.1.13. CORS Support
Cross-origin resource sharing (CORS) is a W3C specification implemented by most browsers that lets you specify in a flexible way what kind of cross-domain requests are authorized., instead of using some less secure and less powerful approaches such as IFRAME or JSONP.
As of version 4.2, Spring MVC supports CORS.
Using controller method CORS configuration with @CrossOrigin
annotations in your Spring Boot application does not require any specific configuration.
Global CORS configuration can be defined by registering a WebMvcConfigurer
bean with a customized addCorsMappings(CorsRegistry)
method, as shown in the following example:
@Configuration(proxyBeanMethods = false)
public class MyConfiguration {
@Bean
public WebMvcConfigurer corsConfigurer() {
return new WebMvcConfigurer() {
@Override
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/api/**");
}
};
}
}
7.2. The “Spring WebFlux Framework”
Spring WebFlux is the new reactive web framework introduced in Spring Framework 5.0. Unlike Spring MVC, it does not require the Servlet API, is fully asynchronous and non-blocking, and implements the Reactive Streams specification through the Reactor project.
Spring WebFlux comes in two flavors: functional and annotation-based. The annotation-based one is quite close to the Spring MVC model, as shown in the following example:
@RestController
@RequestMapping("/users")
public class MyRestController {
@GetMapping("/{user}")
public Mono<User> getUser(@PathVariable Long user) {
// ...
}
@GetMapping("/{user}/customers")
public Flux<Customer> getUserCustomers(@PathVariable Long user) {
// ...
}
@DeleteMapping("/{user}")
public Mono<User> deleteUser(@PathVariable Long user) {
// ...
}
}
“WebFlux.fn”, the functional variant, separates the routing configuration from the actual handling of the requests, as shown in the following example:
@Configuration(proxyBeanMethods = false)
public class RoutingConfiguration {
@Bean
public RouterFunction<ServerResponse> monoRouterFunction(UserHandler userHandler) {
return route(GET("/{user}").and(accept(APPLICATION_JSON)), userHandler::getUser)
.andRoute(GET("/{user}/customers").and(accept(APPLICATION_JSON)), userHandler::getUserCustomers)
.andRoute(DELETE("/{user}").and(accept(APPLICATION_JSON)), userHandler::deleteUser);
}
}
@Component
public class UserHandler {
public Mono<ServerResponse> getUser(ServerRequest request) {
// ...
}
public Mono<ServerResponse> getUserCustomers(ServerRequest request) {
// ...
}
public Mono<ServerResponse> deleteUser(ServerRequest request) {
// ...
}
}
WebFlux is part of the Spring Framework and detailed information is available in its reference documentation.
You can define as many RouterFunction beans as you like to modularize the definition of the router.
Beans can be ordered if you need to apply a precedence.
|
To get started, add the spring-boot-starter-webflux
module to your application.
Adding both spring-boot-starter-web and spring-boot-starter-webflux modules in your application results in Spring Boot auto-configuring Spring MVC, not WebFlux.
This behavior has been chosen because many Spring developers add spring-boot-starter-webflux to their Spring MVC application to use the reactive WebClient .
You can still enforce your choice by setting the chosen application type to SpringApplication.setWebApplicationType(WebApplicationType.REACTIVE) .
|
7.2.1. Spring WebFlux Auto-configuration
Spring Boot provides auto-configuration for Spring WebFlux that works well with most applications.
The auto-configuration adds the following features on top of Spring’s defaults:
-
Configuring codecs for
HttpMessageReader
andHttpMessageWriter
instances (described later in this document). -
Support for serving static resources, including support for WebJars (described later in this document).
If you want to keep Spring Boot WebFlux features and you want to add additional WebFlux configuration, you can add your own @Configuration
class of type WebFluxConfigurer
but without @EnableWebFlux
.
If you want to take complete control of Spring WebFlux, you can add your own @Configuration
annotated with @EnableWebFlux
.
7.2.2. HTTP Codecs with HttpMessageReaders and HttpMessageWriters
Spring WebFlux uses the HttpMessageReader
and HttpMessageWriter
interfaces to convert HTTP requests and responses.
They are configured with CodecConfigurer
to have sensible defaults by looking at the libraries available in your classpath.
Spring Boot provides dedicated configuration properties for codecs, spring.codec.*
.
It also applies further customization by using CodecCustomizer
instances.
For example, spring.jackson.*
configuration keys are applied to the Jackson codec.
If you need to add or customize codecs, you can create a custom CodecCustomizer
component, as shown in the following example:
import org.springframework.boot.web.codec.CodecCustomizer;
@Configuration(proxyBeanMethods = false)
public class MyConfiguration {
@Bean
public CodecCustomizer myCodecCustomizer() {
return codecConfigurer -> {
// ...
};
}
}
You can also leverage Boot’s custom JSON serializers and deserializers.
7.2.3. Static Content
By default, Spring Boot serves static content from a directory called /static
(or /public
or /resources
or /META-INF/resources
) in the classpath.
It uses the ResourceWebHandler
from Spring WebFlux so that you can modify that behavior by adding your own WebFluxConfigurer
and overriding the addResourceHandlers
method.
By default, resources are mapped on /**
, but you can tune that by setting the spring.webflux.static-path-pattern
property.
For instance, relocating all resources to /resources/**
can be achieved as follows:
spring.webflux.static-path-pattern=/resources/**
You can also customize the static resource locations by using spring.resources.static-locations
.
Doing so replaces the default values with a list of directory locations.
If you do so, the default welcome page detection switches to your custom locations.
So, if there is an index.html
in any of your locations on startup, it is the home page of the application.
In addition to the “standard” static resource locations listed earlier, a special case is made for Webjars content.
Any resources with a path in /webjars/**
are served from jar files if they are packaged in the Webjars format.
Spring WebFlux applications do not strictly depend on the Servlet API, so they cannot be deployed as war files and do not use the src/main/webapp directory.
|
7.2.4. Template Engines
As well as REST web services, you can also use Spring WebFlux to serve dynamic HTML content. Spring WebFlux supports a variety of templating technologies, including Thymeleaf, FreeMarker, and Mustache.
Spring Boot includes auto-configuration support for the following templating engines:
When you use one of these templating engines with the default configuration, your templates are picked up automatically from src/main/resources/templates
.
7.2.5. Error Handling
Spring Boot provides a WebExceptionHandler
that handles all errors in a sensible way.
Its position in the processing order is immediately before the handlers provided by WebFlux, which are considered last.
For machine clients, it produces a JSON response with details of the error, the HTTP status, and the exception message.
For browser clients, there is a “whitelabel” error handler that renders the same data in HTML format.
You can also provide your own HTML templates to display errors (see the next section).
The first step to customizing this feature often involves using the existing mechanism but replacing or augmenting the error contents.
For that, you can add a bean of type ErrorAttributes
.
To change the error handling behavior, you can implement ErrorWebExceptionHandler
and register a bean definition of that type.
Because a WebExceptionHandler
is quite low-level, Spring Boot also provides a convenient AbstractErrorWebExceptionHandler
to let you handle errors in a WebFlux functional way, as shown in the following example:
public class CustomErrorWebExceptionHandler extends AbstractErrorWebExceptionHandler {
// Define constructor here
@Override
protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) {
return RouterFunctions
.route(aPredicate, aHandler)
.andRoute(anotherPredicate, anotherHandler);
}
}
For a more complete picture, you can also subclass DefaultErrorWebExceptionHandler
directly and override specific methods.
Custom Error Pages
If you want to display a custom HTML error page for a given status code, you can add a file to an /error
folder.
Error pages can either be static HTML (that is, added under any of the static resource folders) or built with templates.
The name of the file should be the exact status code or a series mask.
For example, to map 404
to a static HTML file, your folder structure would be as follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- public/
+- error/
| +- 404.html
+- <other public assets>
To map all 5xx
errors by using a Mustache template, your folder structure would be as follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- templates/
+- error/
| +- 5xx.mustache
+- <other templates>
7.2.6. Web Filters
Spring WebFlux provides a WebFilter
interface that can be implemented to filter HTTP request-response exchanges.
WebFilter
beans found in the application context will be automatically used to filter each exchange.
Where the order of the filters is important they can implement Ordered
or be annotated with @Order
.
Spring Boot auto-configuration may configure web filters for you.
When it does so, the orders shown in the following table will be used:
Web Filter | Order |
---|---|
|
|
|
|
|
|
7.3. JAX-RS and Jersey
If you prefer the JAX-RS programming model for REST endpoints, you can use one of the available implementations instead of Spring MVC.
Jersey and Apache CXF work quite well out of the box.
CXF requires you to register its Servlet
or Filter
as a @Bean
in your application context.
Jersey has some native Spring support, so we also provide auto-configuration support for it in Spring Boot, together with a starter.
To get started with Jersey, include the spring-boot-starter-jersey
as a dependency and then you need one @Bean
of type ResourceConfig
in which you register all the endpoints, as shown in the following example:
@Component
public class JerseyConfig extends ResourceConfig {
public JerseyConfig() {
register(Endpoint.class);
}
}
Jersey’s support for scanning executable archives is rather limited.
For example, it cannot scan for endpoints in a package found in a fully executable jar file or in WEB-INF/classes when running an executable war file.
To avoid this limitation, the packages method should not be used, and endpoints should be registered individually by using the register method, as shown in the preceding example.
|
For more advanced customizations, you can also register an arbitrary number of beans that implement ResourceConfigCustomizer
.
All the registered endpoints should be @Components
with HTTP resource annotations (@GET
and others), as shown in the following example:
@Component
@Path("/hello")
public class Endpoint {
@GET
public String message() {
return "Hello";
}
}
Since the Endpoint
is a Spring @Component
, its lifecycle is managed by Spring and you can use the @Autowired
annotation to inject dependencies and use the @Value
annotation to inject external configuration.
By default, the Jersey servlet is registered and mapped to /*
.
You can change the mapping by adding @ApplicationPath
to your ResourceConfig
.
By default, Jersey is set up as a Servlet in a @Bean
of type ServletRegistrationBean
named jerseyServletRegistration
.
By default, the servlet is initialized lazily, but you can customize that behavior by setting spring.jersey.servlet.load-on-startup
.
You can disable or override that bean by creating one of your own with the same name.
You can also use a filter instead of a servlet by setting spring.jersey.type=filter
(in which case, the @Bean
to replace or override is jerseyFilterRegistration
).
The filter has an @Order
, which you can set with spring.jersey.filter.order
.
Both the servlet and the filter registrations can be given init parameters by using spring.jersey.init.*
to specify a map of properties.
7.4. Embedded Servlet Container Support
Spring Boot includes support for embedded Tomcat, Jetty, and Undertow servers.
Most developers use the appropriate “Starter” to obtain a fully configured instance.
By default, the embedded server listens for HTTP requests on port 8080
.
7.4.1. Servlets, Filters, and listeners
When using an embedded servlet container, you can register servlets, filters, and all the listeners (such as HttpSessionListener
) from the Servlet spec, either by using Spring beans or by scanning for Servlet components.
Registering Servlets, Filters, and Listeners as Spring Beans
Any Servlet
, Filter
, or servlet *Listener
instance that is a Spring bean is registered with the embedded container.
This can be particularly convenient if you want to refer to a value from your application.properties
during configuration.
By default, if the context contains only a single Servlet, it is mapped to /
.
In the case of multiple servlet beans, the bean name is used as a path prefix.
Filters map to /*
.
If convention-based mapping is not flexible enough, you can use the ServletRegistrationBean
, FilterRegistrationBean
, and ServletListenerRegistrationBean
classes for complete control.
It is usually safe to leave Filter beans unordered.
If a specific order is required, you should annotate the Filter
with @Order
or make it implement Ordered
.
You cannot configure the order of a Filter
by annotating its bean method with @Order
.
If you cannot change the Filter
class to add @Order
or implement Ordered
, you must define a FilterRegistrationBean
for the Filter
and set the registration bean’s order using the setOrder(int)
method.
Avoid configuring a Filter that reads the request body at Ordered.HIGHEST_PRECEDENCE
, since it might go against the character encoding configuration of your application.
If a Servlet filter wraps the request, it should be configured with an order that is less than or equal to OrderedFilter.REQUEST_WRAPPER_FILTER_MAX_ORDER
.
To see the order of every Filter in your application, enable debug level logging for the web logging group (logging.level.web=debug ).
Details of the registered filters, including their order and URL patterns, will then be logged at startup.
|
Take care when registering Filter beans since they are initialized very early in the application lifectyle.
If you need to register a Filter that interacts with other beans, consider using a DelegatingFilterProxyRegistrationBean instead.
|
7.4.2. Servlet Context Initialization
Embedded servlet containers do not directly execute the Servlet 3.0+ javax.servlet.ServletContainerInitializer
interface or Spring’s org.springframework.web.WebApplicationInitializer
interface.
This is an intentional design decision intended to reduce the risk that third party libraries designed to run inside a war may break Spring Boot applications.
If you need to perform servlet context initialization in a Spring Boot application, you should register a bean that implements the org.springframework.boot.web.servlet.ServletContextInitializer
interface.
The single onStartup
method provides access to the ServletContext
and, if necessary, can easily be used as an adapter to an existing WebApplicationInitializer
.
Scanning for Servlets, Filters, and listeners
When using an embedded container, automatic registration of classes annotated with @WebServlet
, @WebFilter
, and @WebListener
can be enabled by using @ServletComponentScan
.
@ServletComponentScan has no effect in a standalone container, where the container’s built-in discovery mechanisms are used instead.
|
7.4.3. The ServletWebServerApplicationContext
Under the hood, Spring Boot uses a different type of ApplicationContext
for embedded servlet container support.
The ServletWebServerApplicationContext
is a special type of WebApplicationContext
that bootstraps itself by searching for a single ServletWebServerFactory
bean.
Usually a TomcatServletWebServerFactory
, JettyServletWebServerFactory
, or UndertowServletWebServerFactory
has been auto-configured.
You usually do not need to be aware of these implementation classes.
Most applications are auto-configured, and the appropriate ApplicationContext and ServletWebServerFactory are created on your behalf.
|
7.4.4. Customizing Embedded Servlet Containers
Common servlet container settings can be configured by using Spring Environment
properties.
Usually, you would define the properties in your application.properties
file.
Common server settings include:
-
Network settings: Listen port for incoming HTTP requests (
server.port
), interface address to bind toserver.address
, and so on. -
Session settings: Whether the session is persistent (
server.servlet.session.persistent
), session timeout (server.servlet.session.timeout
), location of session data (server.servlet.session.store-dir
), and session-cookie configuration (server.servlet.session.cookie.*
). -
Error management: Location of the error page (
server.error.path
) and so on.
Spring Boot tries as much as possible to expose common settings, but this is not always possible.
For those cases, dedicated namespaces offer server-specific customizations (see server.tomcat
and server.undertow
).
For instance, access logs can be configured with specific features of the embedded servlet container.
See the ServerProperties class for a complete list.
|
Programmatic Customization
If you need to programmatically configure your embedded servlet container, you can register a Spring bean that implements the WebServerFactoryCustomizer
interface.
WebServerFactoryCustomizer
provides access to the ConfigurableServletWebServerFactory
, which includes numerous customization setter methods.
The following example shows programmatically setting the port:
import org.springframework.boot.web.server.WebServerFactoryCustomizer;
import org.springframework.boot.web.servlet.server.ConfigurableServletWebServerFactory;
import org.springframework.stereotype.Component;
@Component
public class CustomizationBean implements WebServerFactoryCustomizer<ConfigurableServletWebServerFactory> {
@Override
public void customize(ConfigurableServletWebServerFactory server) {
server.setPort(9000);
}
}
TomcatServletWebServerFactory , JettyServletWebServerFactory and UndertowServletWebServerFactory are dedicated variants of ConfigurableServletWebServerFactory that have additional customization setter methods for Tomcat, Jetty and Undertow respectively.
|
Customizing ConfigurableServletWebServerFactory Directly
If the preceding customization techniques are too limited, you can register the TomcatServletWebServerFactory
, JettyServletWebServerFactory
, or UndertowServletWebServerFactory
bean yourself.
@Bean
public ConfigurableServletWebServerFactory webServerFactory() {
TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
factory.setPort(9000);
factory.setSessionTimeout(10, TimeUnit.MINUTES);
factory.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/notfound.html"));
return factory;
}
Setters are provided for many configuration options. Several protected method “hooks” are also provided should you need to do something more exotic. See the source code documentation for details.
7.4.5. JSP Limitations
When running a Spring Boot application that uses an embedded servlet container (and is packaged as an executable archive), there are some limitations in the JSP support.
-
With Jetty and Tomcat, it should work if you use war packaging. An executable war will work when launched with
java -jar
, and will also be deployable to any standard container. JSPs are not supported when using an executable jar. -
Undertow does not support JSPs.
-
Creating a custom
error.jsp
page does not override the default view for error handling. Custom error pages should be used instead.
7.5. Embedded Reactive Server Support
Spring Boot includes support for the following embedded reactive web servers: Reactor Netty, Tomcat, Jetty, and Undertow. Most developers use the appropriate “Starter” to obtain a fully configured instance. By default, the embedded server listens for HTTP requests on port 8080.
7.6. Reactive Server Resources Configuration
When auto-configuring a Reactor Netty or Jetty server, Spring Boot will create specific beans that will provide HTTP resources to the server instance: ReactorResourceFactory
or JettyResourceFactory
.
By default, those resources will be also shared with the Reactor Netty and Jetty clients for optimal performances, given:
-
the same technology is used for server and client
-
the client instance is built using the
WebClient.Builder
bean auto-configured by Spring Boot
Developers can override the resource configuration for Jetty and Reactor Netty by providing a custom ReactorResourceFactory
or JettyResourceFactory
bean - this will be applied to both clients and servers.
You can learn more about the resource configuration on the client side in the WebClient Runtime section.
8. RSocket
RSocket is a binary protocol for use on byte stream transports. It enables symmetric interaction models via async message passing over a single connection.
The spring-messaging
module of the Spring Framework provides support for RSocket requesters and responders, both on the client and on the server side.
See the RSocket section of the Spring Framework reference for more details, including an overview of the RSocket protocol.
8.1. RSocket Strategies Auto-configuration
Spring Boot auto-configures an RSocketStrategies
bean that provides all the required infrastructure for encoding and decoding RSocket payloads.
By default, the auto-configuration will try to configure the following (in order):
-
CBOR codecs with Jackson
-
JSON codecs with Jackson
The spring-boot-starter-rsocket
starter provides both dependencies.
Check out the Jackson support section to know more about customization possibilities.
Developers can customize the RSocketStrategies
component by creating beans that implement the RSocketStrategiesCustomizer
interface.
Note that their @Order
is important, as it determines the order of codecs.
8.2. RSocket server Auto-configuration
Spring Boot provides RSocket server auto-configuration.
The required dependencies are provided by the spring-boot-starter-rsocket
.
Spring Boot allows exposing RSocket over WebSocket from a WebFlux server, or standing up an independent RSocket server. This depends on the type of application and its configuration.
For WebFlux application (i.e. of type WebApplicationType.REACTIVE
), the RSocket server will be plugged into the Web Server only if the following properties match:
spring.rsocket.server.mapping-path=/rsocket # a mapping path is defined
spring.rsocket.server.transport=websocket # websocket is chosen as a transport
#spring.rsocket.server.port= # no port is defined
Plugging RSocket into a web server is only supported with Reactor Netty, as RSocket itself is built with that library. |
Alternatively, an RSocket TCP or websocket server is started as an independent, embedded server. Besides the dependency requirements, the only required configuration is to define a port for that server:
spring.rsocket.server.port=9898 # the only required configuration
spring.rsocket.server.transport=tcp # you're free to configure other properties
8.3. Spring Messaging RSocket support
Spring Boot will auto-configure the Spring Messaging infrastructure for RSocket.
This means that Spring Boot will create a RSocketMessageHandler
bean that will handle RSocket requests to your application.
8.4. Calling RSocket Services with RSocketRequester
Once the RSocket
channel is established between server and client, any party can send or receive requests to the other.
As a server, you can get injected with an RSocketRequester
instance on any handler method of an RSocket @Controller
.
As a client, you need to configure and establish an RSocket connection first.
Spring Boot auto-configures an RSocketRequester.Builder
for such cases with the expected codecs.
The RSocketRequester.Builder
instance is a prototype bean, meaning each injection point will provide you with a new instance .
This is done on purpose since this builder is stateful and you shouldn’t create requesters with different setups using the same instance.
The following code shows a typical example:
@Service
public class MyService {
private final Mono<RSocketRequester> rsocketRequester;
public MyService(RSocketRequester.Builder rsocketRequesterBuilder) {
this.rsocketRequester = rsocketRequesterBuilder
.connectTcp("example.org", 9898).cache();
}
public Mono<User> someRSocketCall(String name) {
return this.rsocketRequester.flatMap(req ->
req.route("user").data(name).retrieveMono(User.class));
}
}
9. Security
If Spring Security is on the classpath, then web applications are secured by default.
Spring Boot relies on Spring Security’s content-negotiation strategy to determine whether to use httpBasic
or formLogin
.
To add method-level security to a web application, you can also add @EnableGlobalMethodSecurity
with your desired settings.
Additional information can be found in the Spring Security Reference Guide.
The default UserDetailsService
has a single user.
The user name is user
, and the password is random and is printed at INFO level when the application starts, as shown in the following example:
Using generated security password: 78fa095d-3f4c-48b1-ad50-e24c31d5cf35
If you fine-tune your logging configuration, ensure that the org.springframework.boot.autoconfigure.security category is set to log INFO -level messages.
Otherwise, the default password is not printed.
|
You can change the username and password by providing a spring.security.user.name
and spring.security.user.password
.
The basic features you get by default in a web application are:
-
A
UserDetailsService
(orReactiveUserDetailsService
in case of a WebFlux application) bean with in-memory store and a single user with a generated password (seeSecurityProperties.User
for the properties of the user). -
Form-based login or HTTP Basic security (depending on the
Accept
header in the request) for the entire application (including actuator endpoints if actuator is on the classpath). -
A
DefaultAuthenticationEventPublisher
for publishing authentication events.
You can provide a different AuthenticationEventPublisher
by adding a bean for it.
9.1. MVC Security
The default security configuration is implemented in SecurityAutoConfiguration
and UserDetailsServiceAutoConfiguration
.
SecurityAutoConfiguration
imports SpringBootWebSecurityConfiguration
for web security and UserDetailsServiceAutoConfiguration
configures authentication, which is also relevant in non-web applications.
To switch off the default web application security configuration completely or to combine multiple Spring Security components such as OAuth 2 Client and Resource Server, add a bean of type WebSecurityConfigurerAdapter
(doing so does not disable the UserDetailsService
configuration or Actuator’s security).
To also switch off the UserDetailsService
configuration, you can add a bean of type UserDetailsService
, AuthenticationProvider
, or AuthenticationManager
.
Access rules can be overridden by adding a custom WebSecurityConfigurerAdapter
.
Spring Boot provides convenience methods that can be used to override access rules for actuator endpoints and static resources.
EndpointRequest
can be used to create a RequestMatcher
that is based on the management.endpoints.web.base-path
property.
PathRequest
can be used to create a RequestMatcher
for resources in commonly used locations.
9.2. WebFlux Security
Similar to Spring MVC applications, you can secure your WebFlux applications by adding the spring-boot-starter-security
dependency.
The default security configuration is implemented in ReactiveSecurityAutoConfiguration
and UserDetailsServiceAutoConfiguration
.
ReactiveSecurityAutoConfiguration
imports WebFluxSecurityConfiguration
for web security and UserDetailsServiceAutoConfiguration
configures authentication, which is also relevant in non-web applications.
To switch off the default web application security configuration completely, you can add a bean of type WebFilterChainProxy
(doing so does not disable the UserDetailsService
configuration or Actuator’s security).
To also switch off the UserDetailsService
configuration, you can add a bean of type ReactiveUserDetailsService
or ReactiveAuthenticationManager
.
Access rules and the use of multiple Spring Security components such as OAuth 2 Client and Resource Server can be configured by adding a custom SecurityWebFilterChain
bean.
Spring Boot provides convenience methods that can be used to override access rules for actuator endpoints and static resources.
EndpointRequest
can be used to create a ServerWebExchangeMatcher
that is based on the management.endpoints.web.base-path
property.
PathRequest
can be used to create a ServerWebExchangeMatcher
for resources in commonly used locations.
For example, you can customize your security configuration by adding something like:
@Bean
public SecurityWebFilterChain springSecurityFilterChain(ServerHttpSecurity http) {
return http
.authorizeExchange()
.matchers(PathRequest.toStaticResources().atCommonLocations()).permitAll()
.pathMatchers("/foo", "/bar")
.authenticated().and()
.formLogin().and()
.build();
}
9.3. OAuth2
OAuth2 is a widely used authorization framework that is supported by Spring.
9.3.1. Client
If you have spring-security-oauth2-client
on your classpath, you can take advantage of some auto-configuration to make it easy to set up an OAuth2/Open ID Connect clients.
This configuration makes use of the properties under OAuth2ClientProperties
.
The same properties are applicable to both servlet and reactive applications.
You can register multiple OAuth2 clients and providers under the spring.security.oauth2.client
prefix, as shown in the following example:
spring.security.oauth2.client.registration.my-client-1.client-id=abcd
spring.security.oauth2.client.registration.my-client-1.client-secret=password
spring.security.oauth2.client.registration.my-client-1.client-name=Client for user scope
spring.security.oauth2.client.registration.my-client-1.provider=my-oauth-provider
spring.security.oauth2.client.registration.my-client-1.scope=user
spring.security.oauth2.client.registration.my-client-1.redirect-uri=https://my-redirect-uri.com
spring.security.oauth2.client.registration.my-client-1.client-authentication-method=basic
spring.security.oauth2.client.registration.my-client-1.authorization-grant-type=authorization_code
spring.security.oauth2.client.registration.my-client-2.client-id=abcd
spring.security.oauth2.client.registration.my-client-2.client-secret=password
spring.security.oauth2.client.registration.my-client-2.client-name=Client for email scope
spring.security.oauth2.client.registration.my-client-2.provider=my-oauth-provider
spring.security.oauth2.client.registration.my-client-2.scope=email
spring.security.oauth2.client.registration.my-client-2.redirect-uri=https://my-redirect-uri.com
spring.security.oauth2.client.registration.my-client-2.client-authentication-method=basic
spring.security.oauth2.client.registration.my-client-2.authorization-grant-type=authorization_code
spring.security.oauth2.client.provider.my-oauth-provider.authorization-uri=https://my-auth-server/oauth/authorize
spring.security.oauth2.client.provider.my-oauth-provider.token-uri=https://my-auth-server/oauth/token
spring.security.oauth2.client.provider.my-oauth-provider.user-info-uri=https://my-auth-server/userinfo
spring.security.oauth2.client.provider.my-oauth-provider.user-info-authentication-method=header
spring.security.oauth2.client.provider.my-oauth-provider.jwk-set-uri=https://my-auth-server/token_keys
spring.security.oauth2.client.provider.my-oauth-provider.user-name-attribute=name
For OpenID Connect providers that support OpenID Connect discovery, the configuration can be further simplified.
The provider needs to be configured with an issuer-uri
which is the URI that the it asserts as its Issuer Identifier.
For example, if the issuer-uri
provided is "https://example.com", then an OpenID Provider Configuration Request
will be made to "https://example.com/.well-known/openid-configuration".
The result is expected to be an OpenID Provider Configuration Response
.
The following example shows how an OpenID Connect Provider can be configured with the issuer-uri
:
spring.security.oauth2.client.provider.oidc-provider.issuer-uri=https://dev-123456.oktapreview.com/oauth2/default/
By default, Spring Security’s OAuth2LoginAuthenticationFilter
only processes URLs matching /login/oauth2/code/*
.
If you want to customize the redirect-uri
to use a different pattern, you need to provide configuration to process that custom pattern.
For example, for servlet applications, you can add your own WebSecurityConfigurerAdapter
that resembles the following:
public class OAuth2LoginSecurityConfig extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http
.authorizeRequests()
.anyRequest().authenticated()
.and()
.oauth2Login()
.redirectionEndpoint()
.baseUri("/custom-callback");
}
}
OAuth2 client registration for common providers
For common OAuth2 and OpenID providers, including Google, Github, Facebook, and Okta, we provide a set of provider defaults (google
, github
, facebook
, and okta
, respectively).
If you do not need to customize these providers, you can set the provider
attribute to the one for which you need to infer defaults.
Also, if the key for the client registration matches a default supported provider, Spring Boot infers that as well.
In other words, the two configurations in the following example use the Google provider:
spring.security.oauth2.client.registration.my-client.client-id=abcd
spring.security.oauth2.client.registration.my-client.client-secret=password
spring.security.oauth2.client.registration.my-client.provider=google
spring.security.oauth2.client.registration.google.client-id=abcd
spring.security.oauth2.client.registration.google.client-secret=password
9.3.2. Resource Server
If you have spring-security-oauth2-resource-server
on your classpath, Spring Boot can set up an OAuth2 Resource Server.
For JWT configuration, a JWK Set URI or OIDC Issuer URI needs to be specified, as shown in the following examples:
spring.security.oauth2.resourceserver.jwt.jwk-set-uri=https://example.com/oauth2/default/v1/keys
spring.security.oauth2.resourceserver.jwt.issuer-uri=https://dev-123456.oktapreview.com/oauth2/default/
If the authorization server does not support a JWK Set URI, you can configure the resource server with the Public Key used for verifying the signature of the JWT.
This can be done using the spring.security.oauth2.resourceserver.jwt.public-key-location property, where the value needs to point to a file containing the public key in the PEM-encoded x509 format.
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The same properties are applicable for both servlet and reactive applications.
Alternatively, you can define your own JwtDecoder
bean for servlet applications or a ReactiveJwtDecoder
for reactive applications.
In cases where opaque tokens are used instead of JWTs, you can configure the following properties to validate tokens via introspection:
spring.security.oauth2.resourceserver.opaquetoken.introspection-uri=https://example.com/check-token
spring.security.oauth2.resourceserver.opaquetoken.client-id=my-client-id
spring.security.oauth2.resourceserver.opaquetoken.client-secret=my-client-secret
Again, the same properties are applicable for both servlet and reactive applications.
Alternatively, you can define your own OpaqueTokenIntrospector
bean for servlet applications or a ReactiveOpaqueTokenIntrospector
for reactive applications.
9.3.3. Authorization Server
Currently, Spring Security does not provide support for implementing an OAuth 2.0 Authorization Server.
However, this functionality is available from the Spring Security OAuth project, which will eventually be superseded by Spring Security completely.
Until then, you can use the spring-security-oauth2-autoconfigure
module to easily set up an OAuth 2.0 authorization server; see its documentation for instructions.
9.4. SAML 2.0
9.4.1. Relying Party
If you have spring-security-saml2-service-provider
on your classpath, you can take advantage of some auto-configuration to make it easy to set up a SAML 2.0 Relying Party.
This configuration makes use of the properties under Saml2RelyingPartyProperties
.
A relying party registration represents a paired configuration between an Identity Provider, IDP, and a Service Provider, SP.
You can register multiple relying parties under the spring.security.saml2.relyingparty
prefix, as shown in the following example:
spring.security.saml2.relyingparty.registration.my-relying-party1.signing.credentials[0].private-key-location=path-to-private-key
spring.security.saml2.relyingparty.registration.my-relying-party1.signing.credentials[0].certificate-location=path-to-certificate
spring.security.saml2.relyingparty.registration.my-relying-party1.identityprovider.verification.credentials[0].certificate-location=path-to-verification-cert
spring.security.saml2.relyingparty.registration.my-relying-party1.identityprovider.entity-id=remote-idp-entity-id1
spring.security.saml2.relyingparty.registration.my-relying-party1.identityprovider.sso-url=https://remoteidp1.sso.url
spring.security.saml2.relyingparty.registration.my-relying-party2.signing.credentials[0].private-key-location=path-to-private-key
spring.security.saml2.relyingparty.registration.my-relying-party2.signing.credentials[0].certificate-location=path-to-certificate
spring.security.saml2.relyingparty.registration.my-relying-party2.identityprovider.verification.credentials[0].certificate-location=path-to-other-verification-cert
spring.security.saml2.relyingparty.registration.my-relying-party2.identityprovider.entity-id=remote-idp-entity-id2
spring.security.saml2.relyingparty.registration.my-relying-party2.identityprovider.sso-url=https://remoteidp2.sso.url
9.5. Actuator Security
For security purposes, all actuators other than /health
and /info
are disabled by default.
The management.endpoints.web.exposure.include
property can be used to enable the actuators.
If Spring Security is on the classpath and no other WebSecurityConfigurerAdapter is present, all actuators other than /health
and /info
are secured by Spring Boot auto-configuration.
If you define a custom WebSecurityConfigurerAdapter
, Spring Boot auto-configuration will back off and you will be in full control of actuator access rules.
Before setting the management.endpoints.web.exposure.include , ensure that the exposed actuators do not contain sensitive information and/or are secured by placing them behind a firewall or by something like Spring Security.
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9.5.1. Cross Site Request Forgery Protection
Since Spring Boot relies on Spring Security’s defaults, CSRF protection is turned on by default.
This means that the actuator endpoints that require a POST
(shutdown and loggers endpoints), PUT
or DELETE
will get a 403 forbidden error when the default security configuration is in use.
We recommend disabling CSRF protection completely only if you are creating a service that is used by non-browser clients. |
Additional information about CSRF protection can be found in the Spring Security Reference Guide.
10. Working with SQL Databases
The Spring Framework provides extensive support for working with SQL databases, from direct JDBC access using JdbcTemplate
to complete “object relational mapping” technologies such as Hibernate.
Spring Data provides an additional level of functionality: creating Repository
implementations directly from interfaces and using conventions to generate queries from your method names.
10.1. Configure a DataSource
Java’s javax.sql.DataSource
interface provides a standard method of working with database connections.
Traditionally, a 'DataSource' uses a URL
along with some credentials to establish a database connection.
See the “How-to” section for more advanced examples, typically to take full control over the configuration of the DataSource. |
10.1.1. Embedded Database Support
It is often convenient to develop applications by using an in-memory embedded database. Obviously, in-memory databases do not provide persistent storage. You need to populate your database when your application starts and be prepared to throw away data when your application ends.
The “How-to” section includes a section on how to initialize a database. |
Spring Boot can auto-configure embedded H2, HSQL, and Derby databases. You need not provide any connection URLs. You need only include a build dependency to the embedded database that you want to use.
If you are using this feature in your tests, you may notice that the same database is reused by your whole test suite regardless of the number of application contexts that you use.
If you want to make sure that each context has a separate embedded database, you should set |
For example, the typical POM dependencies would be as follows:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.hsqldb</groupId>
<artifactId>hsqldb</artifactId>
<scope>runtime</scope>
</dependency>
You need a dependency on spring-jdbc for an embedded database to be auto-configured.
In this example, it is pulled in transitively through spring-boot-starter-data-jpa .
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If, for whatever reason, you do configure the connection URL for an embedded database, take care to ensure that the database’s automatic shutdown is disabled.
If you use H2, you should use DB_CLOSE_ON_EXIT=FALSE to do so.
If you use HSQLDB, you should ensure that shutdown=true is not used.
Disabling the database’s automatic shutdown lets Spring Boot control when the database is closed, thereby ensuring that it happens once access to the database is no longer needed.
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10.1.2. Connection to a Production Database
Production database connections can also be auto-configured by using a pooling DataSource
.
Spring Boot uses the following algorithm for choosing a specific implementation:
-
We prefer HikariCP for its performance and concurrency. If HikariCP is available, we always choose it.
-
Otherwise, if the Tomcat pooling
DataSource
is available, we use it. -
If neither HikariCP nor the Tomcat pooling datasource are available and if Commons DBCP2 is available, we use it.
If you use the spring-boot-starter-jdbc
or spring-boot-starter-data-jpa
“starters”, you automatically get a dependency to HikariCP
.
You can bypass that algorithm completely and specify the connection pool to use by setting the spring.datasource.type property.
This is especially important if you run your application in a Tomcat container, as tomcat-jdbc is provided by default.
|
Additional connection pools can always be configured manually.
If you define your own DataSource bean, auto-configuration does not occur.
|
DataSource configuration is controlled by external configuration properties in spring.datasource.*
.
For example, you might declare the following section in application.properties
:
spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
You should at least specify the URL by setting the spring.datasource.url property.
Otherwise, Spring Boot tries to auto-configure an embedded database.
|
You often do not need to specify the driver-class-name , since Spring Boot can deduce it for most databases from the url .
|
For a pooling DataSource to be created, we need to be able to verify that a valid Driver class is available, so we check for that before doing anything.
In other words, if you set spring.datasource.driver-class-name=com.mysql.jdbc.Driver , then that class has to be loadable.
|
See DataSourceProperties
for more of the supported options.
These are the standard options that work regardless of the actual implementation.
It is also possible to fine-tune implementation-specific settings by using their respective prefix (spring.datasource.hikari.*
, spring.datasource.tomcat.*
, and spring.datasource.dbcp2.*
).
Refer to the documentation of the connection pool implementation you are using for more details.
For instance, if you use the Tomcat connection pool, you could customize many additional settings, as shown in the following example:
# Number of ms to wait before throwing an exception if no connection is available.
spring.datasource.tomcat.max-wait=10000
# Maximum number of active connections that can be allocated from this pool at the same time.
spring.datasource.tomcat.max-active=50
# Validate the connection before borrowing it from the pool.
spring.datasource.tomcat.test-on-borrow=true
10.1.3. Connection to a JNDI DataSource
If you deploy your Spring Boot application to an Application Server, you might want to configure and manage your DataSource by using your Application Server’s built-in features and access it by using JNDI.
The spring.datasource.jndi-name
property can be used as an alternative to the spring.datasource.url
, spring.datasource.username
, and spring.datasource.password
properties to access the DataSource
from a specific JNDI location.
For example, the following section in application.properties
shows how you can access a JBoss AS defined DataSource
:
spring.datasource.jndi-name=java:jboss/datasources/customers
10.2. Using JdbcTemplate
Spring’s JdbcTemplate
and NamedParameterJdbcTemplate
classes are auto-configured, and you can @Autowire
them directly into your own beans, as shown in the following example:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final JdbcTemplate jdbcTemplate;
@Autowired
public MyBean(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
// ...
}
You can customize some properties of the template by using the spring.jdbc.template.*
properties, as shown in the following example:
spring.jdbc.template.max-rows=500
The NamedParameterJdbcTemplate reuses the same JdbcTemplate instance behind the scenes.
If more than one JdbcTemplate is defined and no primary candidate exists, the NamedParameterJdbcTemplate is not auto-configured.
|
10.3. JPA and Spring Data JPA
The Java Persistence API is a standard technology that lets you “map” objects to relational databases.
The spring-boot-starter-data-jpa
POM provides a quick way to get started.
It provides the following key dependencies:
-
Hibernate: One of the most popular JPA implementations.
-
Spring Data JPA: Makes it easy to implement JPA-based repositories.
-
Spring ORMs: Core ORM support from the Spring Framework.
We do not go into too many details of JPA or Spring Data here. You can follow the “Accessing Data with JPA” guide from spring.io and read the Spring Data JPA and Hibernate reference documentation. |
10.3.1. Entity Classes
Traditionally, JPA “Entity” classes are specified in a persistence.xml
file.
With Spring Boot, this file is not necessary and “Entity Scanning” is used instead.
By default, all packages below your main configuration class (the one annotated with @EnableAutoConfiguration
or @SpringBootApplication
) are searched.
Any classes annotated with @Entity
, @Embeddable
, or @MappedSuperclass
are considered.
A typical entity class resembles the following example:
package com.example.myapp.domain;
import java.io.Serializable;
import javax.persistence.*;
@Entity
public class City implements Serializable {
@Id
@GeneratedValue
private Long id;
@Column(nullable = false)
private String name;
@Column(nullable = false)
private String state;
// ... additional members, often include @OneToMany mappings
protected City() {
// no-args constructor required by JPA spec
// this one is protected since it shouldn't be used directly
}
public City(String name, String state) {
this.name = name;
this.state = state;
}
public String getName() {
return this.name;
}
public String getState() {
return this.state;
}
// ... etc
}
You can customize entity scanning locations by using the @EntityScan annotation.
See the “howto.html” how-to.
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10.3.2. Spring Data JPA Repositories
Spring Data JPA repositories are interfaces that you can define to access data.
JPA queries are created automatically from your method names.
For example, a CityRepository
interface might declare a findAllByState(String state)
method to find all the cities in a given state.
For more complex queries, you can annotate your method with Spring Data’s Query
annotation.
Spring Data repositories usually extend from the Repository
or CrudRepository
interfaces.
If you use auto-configuration, repositories are searched from the package containing your main configuration class (the one annotated with @EnableAutoConfiguration
or @SpringBootApplication
) down.
The following example shows a typical Spring Data repository interface definition:
package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends Repository<City, Long> {
Page<City> findAll(Pageable pageable);
City findByNameAndStateAllIgnoringCase(String name, String state);
}
Spring Data JPA repositories support three different modes of bootstrapping: default, deferred, and lazy.
To enable deferred or lazy bootstrapping, set the spring.data.jpa.repositories.bootstrap-mode
property to deferred
or lazy
respectively.
When using deferred or lazy bootstrapping, the auto-configured EntityManagerFactoryBuilder
will use the context’s AsyncTaskExecutor
, if any, as the bootstrap executor.
If more than one exists, the one named applicationTaskExecutor
will be used.
We have barely scratched the surface of Spring Data JPA. For complete details, see the Spring Data JPA reference documentation. |
10.3.3. Creating and Dropping JPA Databases
By default, JPA databases are automatically created only if you use an embedded database (H2, HSQL, or Derby).
You can explicitly configure JPA settings by using spring.jpa.*
properties.
For example, to create and drop tables you can add the following line to your application.properties
:
spring.jpa.hibernate.ddl-auto=create-drop
Hibernate’s own internal property name for this (if you happen to remember it better) is hibernate.hbm2ddl.auto .
You can set it, along with other Hibernate native properties, by using spring.jpa.properties.* (the prefix is stripped before adding them to the entity manager).
The following line shows an example of setting JPA properties for Hibernate:
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spring.jpa.properties.hibernate.globally_quoted_identifiers=true
The line in the preceding example passes a value of true
for the hibernate.globally_quoted_identifiers
property to the Hibernate entity manager.
By default, the DDL execution (or validation) is deferred until the ApplicationContext
has started.
There is also a spring.jpa.generate-ddl
flag, but it is not used if Hibernate auto-configuration is active, because the ddl-auto
settings are more fine-grained.
10.3.4. Open EntityManager in View
If you are running a web application, Spring Boot by default registers OpenEntityManagerInViewInterceptor
to apply the “Open EntityManager in View” pattern, to allow for lazy loading in web views.
If you do not want this behavior, you should set spring.jpa.open-in-view
to false
in your application.properties
.
10.4. Spring Data JDBC
Spring Data includes repository support for JDBC and will automatically generate SQL for the methods on CrudRepository
.
For more advanced queries, a @Query
annotation is provided.
Spring Boot will auto-configure Spring Data’s JDBC repositories when the necessary dependencies are on the classpath.
They can be added to your project with a single dependency on spring-boot-starter-data-jdbc
.
If necessary, you can take control of Spring Data JDBC’s configuration by adding the @EnableJdbcRepositories
annotation or a JdbcConfiguration
subclass to your application.
For complete details of Spring Data JDBC, please refer to the reference documentation. |
10.5. Using H2’s Web Console
The H2 database provides a browser-based console that Spring Boot can auto-configure for you. The console is auto-configured when the following conditions are met:
-
You are developing a servlet-based web application.
-
com.h2database:h2
is on the classpath. -
You are using Spring Boot’s developer tools.
If you are not using Spring Boot’s developer tools but would still like to make use of H2’s console, you can configure the spring.h2.console.enabled property with a value of true .
|
The H2 console is only intended for use during development, so you should take care to ensure that spring.h2.console.enabled is not set to true in production.
|
10.6. Using jOOQ
jOOQ Object Oriented Querying (jOOQ) is a popular product from Data Geekery which generates Java code from your database and lets you build type-safe SQL queries through its fluent API. Both the commercial and open source editions can be used with Spring Boot.
10.6.1. Code Generation
In order to use jOOQ type-safe queries, you need to generate Java classes from your database schema.
You can follow the instructions in the jOOQ user manual.
If you use the jooq-codegen-maven
plugin and you also use the spring-boot-starter-parent
“parent POM”, you can safely omit the plugin’s <version>
tag.
You can also use Spring Boot-defined version variables (such as h2.version
) to declare the plugin’s database dependency.
The following listing shows an example:
<plugin>
<groupId>org.jooq</groupId>
<artifactId>jooq-codegen-maven</artifactId>
<executions>
...
</executions>
<dependencies>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>${h2.version}</version>
</dependency>
</dependencies>
<configuration>
<jdbc>
<driver>org.h2.Driver</driver>
<url>jdbc:h2:~/yourdatabase</url>
</jdbc>
<generator>
...
</generator>
</configuration>
</plugin>
10.6.2. Using DSLContext
The fluent API offered by jOOQ is initiated through the org.jooq.DSLContext
interface.
Spring Boot auto-configures a DSLContext
as a Spring Bean and connects it to your application DataSource
.
To use the DSLContext
, you can @Autowire
it, as shown in the following example:
@Component
public class JooqExample implements CommandLineRunner {
private final DSLContext create;
@Autowired
public JooqExample(DSLContext dslContext) {
this.create = dslContext;
}
}
The jOOQ manual tends to use a variable named create to hold the DSLContext .
|
You can then use the DSLContext
to construct your queries, as shown in the following example:
public List<GregorianCalendar> authorsBornAfter1980() {
return this.create.selectFrom(AUTHOR)
.where(AUTHOR.DATE_OF_BIRTH.greaterThan(new GregorianCalendar(1980, 0, 1)))
.fetch(AUTHOR.DATE_OF_BIRTH);
}
10.6.3. jOOQ SQL Dialect
Unless the spring.jooq.sql-dialect
property has been configured, Spring Boot determines the SQL dialect to use for your datasource.
If Spring Boot could not detect the dialect, it uses DEFAULT
.
Spring Boot can only auto-configure dialects supported by the open source version of jOOQ. |
10.6.4. Customizing jOOQ
More advanced customizations can be achieved by defining your own @Bean
definitions, which is used when the jOOQ Configuration
is created.
You can define beans for the following jOOQ Types:
-
ConnectionProvider
-
ExecutorProvider
-
TransactionProvider
-
RecordMapperProvider
-
RecordUnmapperProvider
-
Settings
-
RecordListenerProvider
-
ExecuteListenerProvider
-
VisitListenerProvider
-
TransactionListenerProvider
You can also create your own org.jooq.Configuration
@Bean
if you want to take complete control of the jOOQ configuration.
11. Working with NoSQL Technologies
Spring Data provides additional projects that help you access a variety of NoSQL technologies, including:
Spring Boot provides auto-configuration for Redis, MongoDB, Neo4j, Elasticsearch, Solr Cassandra, Couchbase, and LDAP. You can make use of the other projects, but you must configure them yourself. Refer to the appropriate reference documentation at spring.io/projects/spring-data.
11.1. Redis
Redis is a cache, message broker, and richly-featured key-value store. Spring Boot offers basic auto-configuration for the Lettuce and Jedis client libraries and the abstractions on top of them provided by Spring Data Redis.
There is a spring-boot-starter-data-redis
“Starter” for collecting the dependencies in a convenient way.
By default, it uses Lettuce.
That starter handles both traditional and reactive applications.
we also provide a spring-boot-starter-data-redis-reactive “Starter” for consistency with the other stores with reactive support.
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11.1.1. Connecting to Redis
You can inject an auto-configured RedisConnectionFactory
, StringRedisTemplate
, or vanilla RedisTemplate
instance as you would any other Spring Bean.
By default, the instance tries to connect to a Redis server at localhost:6379
.
The following listing shows an example of such a bean:
@Component
public class MyBean {
private StringRedisTemplate template;
@Autowired
public MyBean(StringRedisTemplate template) {
this.template = template;
}
// ...
}
You can also register an arbitrary number of beans that implement LettuceClientConfigurationBuilderCustomizer for more advanced customizations.
If you use Jedis, JedisClientConfigurationBuilderCustomizer is also available.
|
If you add your own @Bean
of any of the auto-configured types, it replaces the default (except in the case of RedisTemplate
, when the exclusion is based on the bean name, redisTemplate
, not its type).
By default, if commons-pool2
is on the classpath, you get a pooled connection factory.
11.2. MongoDB
MongoDB is an open-source NoSQL document database that uses a JSON-like schema instead of traditional table-based relational data.
Spring Boot offers several conveniences for working with MongoDB, including the spring-boot-starter-data-mongodb
and spring-boot-starter-data-mongodb-reactive
“Starters”.
11.2.1. Connecting to a MongoDB Database
To access Mongo databases, you can inject an auto-configured org.springframework.data.mongodb.MongoDatabaseFactory
.
By default, the instance tries to connect to a MongoDB server at mongodb://localhost/test
.
The following example shows how to connect to a MongoDB database:
import org.springframework.data.mongodb.MongoDatabaseFactory;
import com.mongodb.client.MongoDatabase;
@Component
public class MyBean {
private final MongoDatabaseFactory mongo;
@Autowired
public MyBean(MongoDbFactory mongo) {
this.mongo = mongo;
}
// ...
public void example() {
MongoDatabase db = mongo.getMongoDatabase();
// ...
}
}
You can set the spring.data.mongodb.uri
property to change the URL and configure additional settings such as the replica set, as shown in the following example:
spring.data.mongodb.uri=mongodb://user:[email protected]:12345,mongo2.example.com:23456/test
Alternatively, you can specify a host
/port
.
For example, you might declare the following settings in your application.properties
:
spring.data.mongodb.host=mongoserver
spring.data.mongodb.port=27017
If you have defined your own MongoClient
, it will be used to auto-configure a suitable MongoDatabaseFactory
.
If you use the Mongo 3.0 Java driver, spring.data.mongodb.host and spring.data.mongodb.port are not supported.
In such cases, spring.data.mongodb.uri should be used to provide all of the configuration.
|
If spring.data.mongodb.port is not specified, the default of 27017 is used.
You could delete this line from the example shown earlier.
|
If you do not use Spring Data Mongo, you can inject a MongoClient bean instead of using MongoDatabaseFactory .
If you want to take complete control of establishing the MongoDB connection, you can also declare your own MongoDatabaseFactory or MongoClient bean.
|
If you are using the reactive driver, Netty is required for SSL. The auto-configuration configures this factory automatically if Netty is available and the factory to use hasn’t been customized already. |
11.2.2. MongoTemplate
Spring Data MongoDB provides a MongoTemplate
class that is very similar in its design to Spring’s JdbcTemplate
.
As with JdbcTemplate
, Spring Boot auto-configures a bean for you to inject the template, as follows:
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final MongoTemplate mongoTemplate;
public MyBean(MongoTemplate mongoTemplate) {
this.mongoTemplate = mongoTemplate;
}
// ...
}
See the MongoOperations
Javadoc for complete details.
11.2.3. Spring Data MongoDB Repositories
Spring Data includes repository support for MongoDB. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed automatically, based on method names.
In fact, both Spring Data JPA and Spring Data MongoDB share the same common infrastructure.
You could take the JPA example from earlier and, assuming that City
is now a Mongo data class rather than a JPA @Entity
, it works in the same way, as shown in the following example:
package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends Repository<City, Long> {
Page<City> findAll(Pageable pageable);
City findByNameAndStateAllIgnoringCase(String name, String state);
}
You can customize document scanning locations by using the @EntityScan annotation.
|
For complete details of Spring Data MongoDB, including its rich object mapping technologies, refer to its reference documentation. |
11.2.4. Embedded Mongo
Spring Boot offers auto-configuration for Embedded Mongo.
To use it in your Spring Boot application, add a dependency on de.flapdoodle.embed:de.flapdoodle.embed.mongo
.
The port that Mongo listens on can be configured by setting the spring.data.mongodb.port
property.
To use a randomly allocated free port, use a value of 0.
The MongoClient
created by MongoAutoConfiguration
is automatically configured to use the randomly allocated port.
If you do not configure a custom port, the embedded support uses a random port (rather than 27017) by default. |
If you have SLF4J on the classpath, the output produced by Mongo is automatically routed to a logger named org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongo
.
You can declare your own IMongodConfig
and IRuntimeConfig
beans to take control of the Mongo instance’s configuration and logging routing.
The download configuration can be customized by declaring a DownloadConfigBuilderCustomizer
bean.
11.3. Neo4j
Neo4j is an open-source NoSQL graph database that uses a rich data model of nodes connected by first class relationships, which is better suited for connected big data than traditional RDBMS approaches.
Spring Boot offers several conveniences for working with Neo4j, including the spring-boot-starter-data-neo4j
“Starter”.
11.3.1. Connecting to a Neo4j Database
To access a Neo4j server, you can inject an auto-configured org.neo4j.ogm.session.Session
.
By default, the instance tries to connect to a Neo4j server at localhost:7687
using the Bolt protocol.
The following example shows how to inject a Neo4j Session
:
@Component
public class MyBean {
private final Session session;
@Autowired
public MyBean(Session session) {
this.session = session;
}
// ...
}
You can configure the uri and credentials to use by setting the spring.data.neo4j.*
properties, as shown in the following example:
spring.data.neo4j.uri=bolt://my-server:7687
spring.data.neo4j.username=neo4j
spring.data.neo4j.password=secret
You can take full control over the session creation by adding either an org.neo4j.ogm.config.Configuration
bean or an org.neo4j.ogm.session.SessionFactory
bean.
11.3.2. Using the Embedded Mode
If you add org.neo4j:neo4j-ogm-embedded-driver
to the dependencies of your application, Spring Boot automatically configures an in-process embedded instance of Neo4j that does not persist any data when your application shuts down.
As the embedded Neo4j OGM driver does not provide the Neo4j kernel itself, you have to declare org.neo4j:neo4j as dependency yourself.
Refer to the Neo4j OGM documentation for a list of compatible versions.
|
The embedded driver takes precedence over the other drivers when there are multiple drivers on the classpath.
You can explicitly disable the embedded mode by setting spring.data.neo4j.embedded.enabled=false
.
Data Neo4j Tests automatically make use of an embedded Neo4j instance if the embedded driver and Neo4j kernel are on the classpath as described above.
You can enable persistence for the embedded mode by providing a path to a database file in your configuration, e.g. spring.data.neo4j.uri=file://var/tmp/graph.db .
|
11.3.3. Using Native Types
Neo4j-OGM can map some types, like those in java.time.*
, to String
-based properties or to one of the native types that Neo4j provides.
For backwards compatibility reasons the default for Neo4j-OGM is to use a String
-based representation.
To use native types, add a dependency on either org.neo4j:neo4j-ogm-bolt-native-types
or org.neo4j:neo4j-ogm-embedded-native-types
, and configure the spring.data.neo4j.use-native-types
property as shown in the following example:
spring.data.neo4j.use-native-types=true
11.3.4. Neo4jSession
By default, if you are running a web application, the session is bound to the thread for the entire processing of the request (that is, it uses the "Open Session in View" pattern).
If you do not want this behavior, add the following line to your application.properties
file:
spring.data.neo4j.open-in-view=false
11.3.5. Spring Data Neo4j Repositories
Spring Data includes repository support for Neo4j.
Spring Data Neo4j shares the common infrastructure with Spring Data JPA as many other Spring Data modules do.
You could take the JPA example from earlier and define City
as Neo4j OGM @NodeEntity
rather than JPA @Entity
and the repository abstraction works in the same way, as shown in the following example:
package com.example.myapp.domain;
import java.util.Optional;
import org.springframework.data.neo4j.repository.*;
public interface CityRepository extends Neo4jRepository<City, Long> {
Optional<City> findOneByNameAndState(String name, String state);
}
The spring-boot-starter-data-neo4j
“Starter” enables the repository support as well as transaction management.
You can customize the locations to look for repositories and entities by using @EnableNeo4jRepositories
and @EntityScan
respectively on a @Configuration
-bean.
For complete details of Spring Data Neo4j, including its object mapping technologies, refer to the reference documentation. |
11.4. Solr
Apache Solr is a search engine.
Spring Boot offers basic auto-configuration for the Solr 5 client library and the abstractions on top of it provided by Spring Data Solr.
There is a spring-boot-starter-data-solr
“Starter” for collecting the dependencies in a convenient way.
11.4.1. Connecting to Solr
You can inject an auto-configured SolrClient
instance as you would any other Spring bean.
By default, the instance tries to connect to a server at localhost:8983/solr
.
The following example shows how to inject a Solr bean:
@Component
public class MyBean {
private SolrClient solr;
@Autowired
public MyBean(SolrClient solr) {
this.solr = solr;
}
// ...
}
If you add your own @Bean
of type SolrClient
, it replaces the default.
11.4.2. Spring Data Solr Repositories
Spring Data includes repository support for Apache Solr. As with the JPA repositories discussed earlier, the basic principle is that queries are automatically constructed for you based on method names.
In fact, both Spring Data JPA and Spring Data Solr share the same common infrastructure.
You could take the JPA example from earlier and, assuming that City
is now a @SolrDocument
class rather than a JPA @Entity
, it works in the same way.
IP: For complete details of Spring Data Solr, refer to the reference documentation.
11.5. Elasticsearch
Elasticsearch is an open source, distributed, RESTful search and analytics engine. Spring Boot offers basic auto-configuration for Elasticsearch.
Spring Boot supports several clients:
-
The official Java "Low Level" and "High Level" REST clients
-
The
ReactiveElasticsearchClient
provided by Spring Data Elasticsearch
Spring Boot provides a dedicated “Starter”, spring-boot-starter-data-elasticsearch
.
11.5.1. Connecting to Elasticsearch using REST clients
Elasticsearch ships two different REST clients that you can use to query a cluster: the "Low Level" client and the "High Level" client.
If you have the org.elasticsearch.client:elasticsearch-rest-client
dependency on the classpath, Spring Boot will auto-configure and register a RestClient
bean that by default targets localhost:9200
.
You can further tune how RestClient
is configured, as shown in the following example:
spring.elasticsearch.rest.uris=https://search.example.com:9200
spring.elasticsearch.rest.read-timeout=10s
spring.elasticsearch.rest.username=user
spring.elasticsearch.rest.password=secret
You can also register an arbitrary number of beans that implement RestClientBuilderCustomizer
for more advanced customizations.
To take full control over the registration, define a RestClient
bean.
If you have the org.elasticsearch.client:elasticsearch-rest-high-level-client
dependency on the classpath, Spring Boot will auto-configure a RestHighLevelClient
, which wraps any existing RestClient
bean, reusing its HTTP configuration.
11.5.2. Connecting to Elasticsearch using Reactive REST clients
Spring Data Elasticsearch ships ReactiveElasticsearchClient
for querying Elasticsearch instances in a reactive fashion.
It is built on top of WebFlux’s WebClient
, so both spring-boot-starter-elasticsearch
and spring-boot-starter-webflux
dependencies are useful to enable this support.
By default, Spring Boot will auto-configure and register a ReactiveElasticsearchClient
bean that targets localhost:9200
.
You can further tune how it is configured, as shown in the following example:
spring.data.elasticsearch.client.reactive.endpoints=search.example.com:9200
spring.data.elasticsearch.client.reactive.use-ssl=true
spring.data.elasticsearch.client.reactive.socket-timeout=10s
spring.data.elasticsearch.client.reactive.username=user
spring.data.elasticsearch.client.reactive.password=secret
If the configuration properties are not enough and you’d like to fully control the client
configuration, you can register a custom ClientConfiguration
bean.
11.5.3. Connecting to Elasticsearch by Using Spring Data
To connect to Elasticsearch, a RestHighLevelClient
bean must be defined,
auto-configured by Spring Boot or manually provided by the application (see previous sections).
With this configuration in place, an
ElasticsearchRestTemplate
can be injected like any other Spring bean,
as shown in the following example:
@Component
public class MyBean {
private final ElasticsearchRestTemplate template;
public MyBean(ElasticsearchRestTemplate template) {
this.template = template;
}
// ...
}
In the presence of spring-data-elasticsearch
and the required dependencies for using a WebClient
(typically spring-boot-starter-webflux
), Spring Boot can also auto-configure a ReactiveElasticsearchClient and a ReactiveElasticsearchTemplate
as beans.
They are the reactive equivalent of the other REST clients.
11.5.4. Spring Data Elasticsearch Repositories
Spring Data includes repository support for Elasticsearch. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.
In fact, both Spring Data JPA and Spring Data Elasticsearch share the same common infrastructure.
You could take the JPA example from earlier and, assuming that City
is now an Elasticsearch @Document
class rather than a JPA @Entity
, it works in the same way.
For complete details of Spring Data Elasticsearch, refer to the reference documentation. |
Spring Boot supports both classic and reactive Elasticsearch repositories, using the ElasticsearchRestTemplate
or ReactiveElasticsearchTemplate
beans.
Most likely those beans are auto-configured by Spring Boot given the required dependencies are present.
If you wish to use your own template for backing the Elasticsearch repositories, you can add your own ElasticsearchRestTemplate
or ElasticsearchOperations
@Bean
, as long as it is named "elasticsearchTemplate"
.
Same applies to ReactiveElasticsearchTemplate
and ReactiveElasticsearchOperations
, with the bean name "reactiveElasticsearchTemplate"
.
You can choose to disable the repositories support with the following property:
spring.data.elasticsearch.repositories.enabled=false
11.6. Cassandra
Cassandra is an open source, distributed database management system designed to handle large amounts of data across many commodity servers.
Spring Boot offers auto-configuration for Cassandra and the abstractions on top of it provided by Spring Data Cassandra.
There is a spring-boot-starter-data-cassandra
“Starter” for collecting the dependencies in a convenient way.
11.6.1. Connecting to Cassandra
You can inject an auto-configured CassandraTemplate
or a Cassandra CqlSession
instance as you would with any other Spring Bean.
The spring.data.cassandra.*
properties can be used to customize the connection.
Generally, you provide keyspace-name
and contact-points
as well the local datacenter name, as shown in the following example:
spring.data.cassandra.keyspace-name=mykeyspace
spring.data.cassandra.contact-points=cassandrahost1:9042,cassandrahost2:9042
spring.data.cassandra.local-datacenter=datacenter1
You can also register an arbitrary number of beans that implement DriverConfigLoaderBuilderCustomizer
for more advanced driver customizations.
The CqlSession
can be customized with a bean of type CqlSessionBuilderCustomizer
.
If you’re using CqlSessionBuilder to create multiple CqlSession beans, keep in mind the builder is mutable so make sure to inject a fresh copy for each session.
|
The following code listing shows how to inject a Cassandra bean:
@Component
public class MyBean {
private final CassandraTemplate template;
public MyBean(CassandraTemplate template) {
this.template = template;
}
// ...
}
If you add your own @Bean
of type CassandraTemplate
, it replaces the default.
11.6.2. Spring Data Cassandra Repositories
Spring Data includes basic repository support for Cassandra.
Currently, this is more limited than the JPA repositories discussed earlier and needs to annotate finder methods with @Query
.
For complete details of Spring Data Cassandra, refer to the reference documentation. |
11.7. Couchbase
Couchbase is an open-source, distributed, multi-model NoSQL document-oriented database that is optimized for interactive applications.
Spring Boot offers auto-configuration for Couchbase and the abstractions on top of it provided by Spring Data Couchbase.
There are spring-boot-starter-data-couchbase
and spring-boot-starter-data-couchbase-reactive
“Starters” for collecting the dependencies in a convenient way.
11.7.1. Connecting to Couchbase
You can get a Bucket
and Cluster
by adding the Couchbase SDK and some configuration.
The spring.couchbase.*
properties can be used to customize the connection.
Generally, you provide the bootstrap hosts, bucket name, and password, as shown in the following example:
spring.couchbase.bootstrap-hosts=my-host-1,192.168.1.123
spring.couchbase.bucket.name=my-bucket
spring.couchbase.bucket.password=secret
You need to provide at least the bootstrap host(s), in which case the bucket name is default and the password is an empty String.
Alternatively, you can define your own org.springframework.data.couchbase.config.CouchbaseConfigurer @Bean to take control over the whole configuration.
|
It is also possible to customize some of the CouchbaseEnvironment
settings.
For instance, the following configuration changes the timeout to use to open a new Bucket
and enables SSL support:
spring.couchbase.env.timeouts.connect=3000
spring.couchbase.env.ssl.key-store=/location/of/keystore.jks
spring.couchbase.env.ssl.key-store-password=secret
Check the spring.couchbase.env.*
properties for more details.
11.7.2. Spring Data Couchbase Repositories
Spring Data includes repository support for Couchbase. For complete details of Spring Data Couchbase, refer to the reference documentation.
You can inject an auto-configured CouchbaseTemplate
instance as you would with any other Spring Bean, provided a default CouchbaseConfigurer
is available (which happens when you enable Couchbase support, as explained earlier).
The following examples shows how to inject a Couchbase bean:
@Component
public class MyBean {
private final CouchbaseTemplate template;
@Autowired
public MyBean(CouchbaseTemplate template) {
this.template = template;
}
// ...
}
There are a few beans that you can define in your own configuration to override those provided by the auto-configuration:
-
A
CouchbaseTemplate
@Bean
with a name ofcouchbaseTemplate
. -
An
IndexManager
@Bean
with a name ofcouchbaseIndexManager
. -
A
CustomConversions
@Bean
with a name ofcouchbaseCustomConversions
.
To avoid hard-coding those names in your own config, you can reuse BeanNames
provided by Spring Data Couchbase.
For instance, you can customize the converters to use, as follows:
@Configuration(proxyBeanMethods = false)
public class SomeConfiguration {
@Bean(BeanNames.COUCHBASE_CUSTOM_CONVERSIONS)
public CustomConversions myCustomConversions() {
return new CustomConversions(...);
}
// ...
}
If you want to fully bypass the auto-configuration for Spring Data Couchbase, provide your own implementation of org.springframework.data.couchbase.config.AbstractCouchbaseDataConfiguration .
|
11.8. LDAP
LDAP (Lightweight Directory Access Protocol) is an open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an IP network. Spring Boot offers auto-configuration for any compliant LDAP server as well as support for the embedded in-memory LDAP server from UnboundID.
LDAP abstractions are provided by Spring Data LDAP.
There is a spring-boot-starter-data-ldap
“Starter” for collecting the dependencies in a convenient way.
11.8.1. Connecting to an LDAP Server
To connect to an LDAP server, make sure you declare a dependency on the spring-boot-starter-data-ldap
“Starter” or spring-ldap-core
and then declare the URLs of your server in your application.properties, as shown in the following example:
spring.ldap.urls=ldap://myserver:1235
spring.ldap.username=admin
spring.ldap.password=secret
If you need to customize connection settings, you can use the spring.ldap.base
and spring.ldap.base-environment
properties.
An LdapContextSource
is auto-configured based on these settings.
If a DirContextAuthenticationStrategy
bean is available, it is associated to the auto-configured LdapContextSource
.
If you need to customize it, for instance to use a PooledContextSource
, you can still inject the auto-configured LdapContextSource
.
Make sure to flag your customized ContextSource
as @Primary
so that the auto-configured LdapTemplate
uses it.
11.8.2. Spring Data LDAP Repositories
Spring Data includes repository support for LDAP. For complete details of Spring Data LDAP, refer to the reference documentation.
You can also inject an auto-configured LdapTemplate
instance as you would with any other Spring Bean, as shown in the following example:
@Component
public class MyBean {
private final LdapTemplate template;
@Autowired
public MyBean(LdapTemplate template) {
this.template = template;
}
// ...
}
11.8.3. Embedded In-memory LDAP Server
For testing purposes, Spring Boot supports auto-configuration of an in-memory LDAP server from UnboundID.
To configure the server, add a dependency to com.unboundid:unboundid-ldapsdk
and declare a spring.ldap.embedded.base-dn
property, as follows:
spring.ldap.embedded.base-dn=dc=spring,dc=io
It is possible to define multiple base-dn values, however, since distinguished names usually contain commas, they must be defined using the correct notation. In yaml files, you can use the yaml list notation:
In properties files, you must include the index as part of the property name:
|
By default, the server starts on a random port and triggers the regular LDAP support.
There is no need to specify a spring.ldap.urls
property.
If there is a schema.ldif
file on your classpath, it is used to initialize the server.
If you want to load the initialization script from a different resource, you can also use the spring.ldap.embedded.ldif
property.
By default, a standard schema is used to validate LDIF
files.
You can turn off validation altogether by setting the spring.ldap.embedded.validation.enabled
property.
If you have custom attributes, you can use spring.ldap.embedded.validation.schema
to define your custom attribute types or object classes.
11.9. InfluxDB
InfluxDB is an open-source time series database optimized for fast, high-availability storage and retrieval of time series data in fields such as operations monitoring, application metrics, Internet-of-Things sensor data, and real-time analytics.
11.9.1. Connecting to InfluxDB
Spring Boot auto-configures an InfluxDB
instance, provided the influxdb-java
client is on the classpath and the URL of the database is set, as shown in the following example:
spring.influx.url=https://172.0.0.1:8086
If the connection to InfluxDB requires a user and password, you can set the spring.influx.user
and spring.influx.password
properties accordingly.
InfluxDB relies on OkHttp.
If you need to tune the http client InfluxDB
uses behind the scenes, you can register an InfluxDbOkHttpClientBuilderProvider
bean.
12. Caching
The Spring Framework provides support for transparently adding caching to an application.
At its core, the abstraction applies caching to methods, thus reducing the number of executions based on the information available in the cache.
The caching logic is applied transparently, without any interference to the invoker.
Spring Boot auto-configures the cache infrastructure as long as caching support is enabled via the @EnableCaching
annotation.
Check the relevant section of the Spring Framework reference for more details. |
In a nutshell, adding caching to an operation of your service is as easy as adding the relevant annotation to its method, as shown in the following example:
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Component;
@Component
public class MathService {
@Cacheable("piDecimals")
public int computePiDecimal(int i) {
// ...
}
}
This example demonstrates the use of caching on a potentially costly operation.
Before invoking computePiDecimal
, the abstraction looks for an entry in the piDecimals
cache that matches the i
argument.
If an entry is found, the content in the cache is immediately returned to the caller, and the method is not invoked.
Otherwise, the method is invoked, and the cache is updated before returning the value.
You can also use the standard JSR-107 (JCache) annotations (such as @CacheResult ) transparently.
However, we strongly advise you to not mix and match the Spring Cache and JCache annotations.
|
If you do not add any specific cache library, Spring Boot auto-configures a simple provider that uses concurrent maps in memory.
When a cache is required (such as piDecimals
in the preceding example), this provider creates it for you.
The simple provider is not really recommended for production usage, but it is great for getting started and making sure that you understand the features.
When you have made up your mind about the cache provider to use, please make sure to read its documentation to figure out how to configure the caches that your application uses.
Nearly all providers require you to explicitly configure every cache that you use in the application.
Some offer a way to customize the default caches defined by the spring.cache.cache-names
property.
12.1. Supported Cache Providers
The cache abstraction does not provide an actual store and relies on abstraction materialized by the org.springframework.cache.Cache
and org.springframework.cache.CacheManager
interfaces.
If you have not defined a bean of type CacheManager
or a CacheResolver
named cacheResolver
(see CachingConfigurer
), Spring Boot tries to detect the following providers (in the indicated order):
-
JCache (JSR-107) (EhCache 3, Hazelcast, Infinispan, and others)
It is also possible to force a particular cache provider by setting the spring.cache.type property.
Use this property if you need to disable caching altogether in certain environment (such as tests).
|
Use the spring-boot-starter-cache “Starter” to quickly add basic caching dependencies.
The starter brings in spring-context-support .
If you add dependencies manually, you must include spring-context-support in order to use the JCache, EhCache 2.x, or Caffeine support.
|
If the CacheManager
is auto-configured by Spring Boot, you can further tune its configuration before it is fully initialized by exposing a bean that implements the CacheManagerCustomizer
interface.
The following example sets a flag to say that null
values should be passed down to the underlying map:
@Bean
public CacheManagerCustomizer<ConcurrentMapCacheManager> cacheManagerCustomizer() {
return new CacheManagerCustomizer<ConcurrentMapCacheManager>() {
@Override
public void customize(ConcurrentMapCacheManager cacheManager) {
cacheManager.setAllowNullValues(false);
}
};
}
In the preceding example, an auto-configured ConcurrentMapCacheManager is expected.
If that is not the case (either you provided your own config or a different cache provider was auto-configured), the customizer is not invoked at all.
You can have as many customizers as you want, and you can also order them by using @Order or Ordered .
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12.1.1. Generic
Generic caching is used if the context defines at least one org.springframework.cache.Cache
bean.
A CacheManager
wrapping all beans of that type is created.
12.1.2. JCache (JSR-107)
JCache is bootstrapped through the presence of a javax.cache.spi.CachingProvider
on the classpath (that is, a JSR-107 compliant caching library exists on the classpath), and the JCacheCacheManager
is provided by the spring-boot-starter-cache
“Starter”.
Various compliant libraries are available, and Spring Boot provides dependency management for Ehcache 3, Hazelcast, and Infinispan.
Any other compliant library can be added as well.
It might happen that more than one provider is present, in which case the provider must be explicitly specified. Even if the JSR-107 standard does not enforce a standardized way to define the location of the configuration file, Spring Boot does its best to accommodate setting a cache with implementation details, as shown in the following example:
# Only necessary if more than one provider is present
spring.cache.jcache.provider=com.acme.MyCachingProvider
spring.cache.jcache.config=classpath:acme.xml
When a cache library offers both a native implementation and JSR-107 support, Spring Boot prefers the JSR-107 support, so that the same features are available if you switch to a different JSR-107 implementation. |
Spring Boot has general support for Hazelcast.
If a single HazelcastInstance is available, it is automatically reused for the CacheManager as well, unless the spring.cache.jcache.config property is specified.
|
There are two ways to customize the underlying javax.cache.cacheManager
:
-
Caches can be created on startup by setting the
spring.cache.cache-names
property. If a customjavax.cache.configuration.Configuration
bean is defined, it is used to customize them. -
org.springframework.boot.autoconfigure.cache.JCacheManagerCustomizer
beans are invoked with the reference of theCacheManager
for full customization.
If a standard javax.cache.CacheManager bean is defined, it is wrapped automatically in an org.springframework.cache.CacheManager implementation that the abstraction expects.
No further customization is applied to it.
|
12.1.3. EhCache 2.x
EhCache 2.x is used if a file named ehcache.xml
can be found at the root of the classpath.
If EhCache 2.x is found, the EhCacheCacheManager
provided by the spring-boot-starter-cache
“Starter” is used to bootstrap the cache manager.
An alternate configuration file can be provided as well, as shown in the following example:
spring.cache.ehcache.config=classpath:config/another-config.xml
12.1.4. Hazelcast
Spring Boot has general support for Hazelcast.
If a HazelcastInstance
has been auto-configured, it is automatically wrapped in a CacheManager
.
12.1.5. Infinispan
Infinispan has no default configuration file location, so it must be specified explicitly. Otherwise, the default bootstrap is used.
spring.cache.infinispan.config=infinispan.xml
Caches can be created on startup by setting the spring.cache.cache-names
property.
If a custom ConfigurationBuilder
bean is defined, it is used to customize the caches.
The support of Infinispan in Spring Boot is restricted to the embedded mode and is quite basic. If you want more options, you should use the official Infinispan Spring Boot starter instead. See Infinispan’s documentation for more details. |
12.1.6. Couchbase
If the Couchbase Java client and the couchbase-spring-cache
implementation are available and Couchbase is configured, a CouchbaseCacheManager
is auto-configured.
It is also possible to create additional caches on startup by setting the spring.cache.cache-names
property.
These caches operate on the Bucket
that was auto-configured.
You can also create additional caches on another Bucket
by using the customizer.
Assume you need two caches (cache1
and cache2
) on the "main" Bucket
and one (cache3
) cache with a custom time to live of 2 seconds on the “another” Bucket
.
You can create the first two caches through configuration, as follows:
spring.cache.cache-names=cache1,cache2
Then you can define a @Configuration
class to configure the extra Bucket
and the cache3
cache, as follows:
@Configuration(proxyBeanMethods = false)
public class CouchbaseCacheConfiguration {
private final Cluster cluster;
public CouchbaseCacheConfiguration(Cluster cluster) {
this.cluster = cluster;
}
@Bean
public Bucket anotherBucket() {
return this.cluster.openBucket("another", "secret");
}
@Bean
public CacheManagerCustomizer<CouchbaseCacheManager> cacheManagerCustomizer() {
return c -> {
c.prepareCache("cache3", CacheBuilder.newInstance(anotherBucket())
.withExpiration(2));
};
}
}
This sample configuration reuses the Cluster
that was created through auto-configuration.
12.1.7. Redis
If Redis is available and configured, a RedisCacheManager
is auto-configured.
It is possible to create additional caches on startup by setting the spring.cache.cache-names
property and cache defaults can be configured by using spring.cache.redis.*
properties.
For instance, the following configuration creates cache1
and cache2
caches with a time to live of 10 minutes:
spring.cache.cache-names=cache1,cache2
spring.cache.redis.time-to-live=600000
By default, a key prefix is added so that, if two separate caches use the same key, Redis does not have overlapping keys and cannot return invalid values.
We strongly recommend keeping this setting enabled if you create your own RedisCacheManager .
|
You can take full control of the default configuration by adding a RedisCacheConfiguration @Bean of your own.
This can be useful if you’re looking for customizing the default serialization strategy.
|
If you need more control over the configuration, consider registering a RedisCacheManagerBuilderCustomizer
bean.
The following example shows a customizer that configures a specific time to live for cache1
and cache2
:
@Bean
public RedisCacheManagerBuilderCustomizer myRedisCacheManagerBuilderCustomizer() {
return (builder) -> builder
.withCacheConfiguration("cache1",
RedisCacheConfiguration.defaultCacheConfig().entryTtl(Duration.ofSeconds(10)))
.withCacheConfiguration("cache2",
RedisCacheConfiguration.defaultCacheConfig().entryTtl(Duration.ofMinutes(1)));
}
12.1.8. Caffeine
Caffeine is a Java 8 rewrite of Guava’s cache that supersedes support for Guava.
If Caffeine is present, a CaffeineCacheManager
(provided by the spring-boot-starter-cache
“Starter”) is auto-configured.
Caches can be created on startup by setting the spring.cache.cache-names
property and can be customized by one of the following (in the indicated order):
-
A cache spec defined by
spring.cache.caffeine.spec
-
A
com.github.benmanes.caffeine.cache.CaffeineSpec
bean is defined -
A
com.github.benmanes.caffeine.cache.Caffeine
bean is defined
For instance, the following configuration creates cache1
and cache2
caches with a maximum size of 500 and a time to live of 10 minutes
spring.cache.cache-names=cache1,cache2
spring.cache.caffeine.spec=maximumSize=500,expireAfterAccess=600s
If a com.github.benmanes.caffeine.cache.CacheLoader
bean is defined, it is automatically associated to the CaffeineCacheManager
.
Since the CacheLoader
is going to be associated with all caches managed by the cache manager, it must be defined as CacheLoader<Object, Object>
.
The auto-configuration ignores any other generic type.
12.1.9. Simple
If none of the other providers can be found, a simple implementation using a ConcurrentHashMap
as the cache store is configured.
This is the default if no caching library is present in your application.
By default, caches are created as needed, but you can restrict the list of available caches by setting the cache-names
property.
For instance, if you want only cache1
and cache2
caches, set the cache-names
property as follows:
spring.cache.cache-names=cache1,cache2
If you do so and your application uses a cache not listed, then it fails at runtime when the cache is needed, but not on startup. This is similar to the way the "real" cache providers behave if you use an undeclared cache.
12.1.10. None
When @EnableCaching
is present in your configuration, a suitable cache configuration is expected as well.
If you need to disable caching altogether in certain environments, force the cache type to none
to use a no-op implementation, as shown in the following example:
spring.cache.type=none
13. Messaging
The Spring Framework provides extensive support for integrating with messaging systems, from simplified use of the JMS API using JmsTemplate
to a complete infrastructure to receive messages asynchronously.
Spring AMQP provides a similar feature set for the Advanced Message Queuing Protocol.
Spring Boot also provides auto-configuration options for RabbitTemplate
and RabbitMQ.
Spring WebSocket natively includes support for STOMP messaging, and Spring Boot has support for that through starters and a small amount of auto-configuration.
Spring Boot also has support for Apache Kafka.
13.1. JMS
The javax.jms.ConnectionFactory
interface provides a standard method of creating a javax.jms.Connection
for interacting with a JMS broker.
Although Spring needs a ConnectionFactory
to work with JMS, you generally need not use it directly yourself and can instead rely on higher level messaging abstractions.
(See the relevant section of the Spring Framework reference documentation for details.)
Spring Boot also auto-configures the necessary infrastructure to send and receive messages.
13.1.1. ActiveMQ Support
When ActiveMQ is available on the classpath, Spring Boot can also configure a ConnectionFactory
.
If the broker is present, an embedded broker is automatically started and configured (provided no broker URL is specified through configuration).
If you use spring-boot-starter-activemq , the necessary dependencies to connect or embed an ActiveMQ instance are provided, as is the Spring infrastructure to integrate with JMS.
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ActiveMQ configuration is controlled by external configuration properties in spring.activemq.*
.
For example, you might declare the following section in application.properties
:
spring.activemq.broker-url=tcp://192.168.1.210:9876
spring.activemq.user=admin
spring.activemq.password=secret
By default, a CachingConnectionFactory
wraps the native ConnectionFactory
with sensible settings that you can control by external configuration properties in spring.jms.*
:
spring.jms.cache.session-cache-size=5
If you’d rather use native pooling, you can do so by adding a dependency to org.messaginghub:pooled-jms
and configuring the JmsPoolConnectionFactory
accordingly, as shown in the following example:
spring.activemq.pool.enabled=true
spring.activemq.pool.max-connections=50
See ActiveMQProperties for more of the supported options.
You can also register an arbitrary number of beans that implement ActiveMQConnectionFactoryCustomizer for more advanced customizations.
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By default, ActiveMQ creates a destination if it does not yet exist so that destinations are resolved against their provided names.
13.1.2. Artemis Support
Spring Boot can auto-configure a ConnectionFactory
when it detects that Artemis is available on the classpath.
If the broker is present, an embedded broker is automatically started and configured (unless the mode property has been explicitly set).
The supported modes are embedded
(to make explicit that an embedded broker is required and that an error should occur if the broker is not available on the classpath) and native
(to connect to a broker using the netty
transport protocol).
When the latter is configured, Spring Boot configures a ConnectionFactory
that connects to a broker running on the local machine with the default settings.
If you use spring-boot-starter-artemis , the necessary dependencies to connect to an existing Artemis instance are provided, as well as the Spring infrastructure to integrate with JMS.
Adding org.apache.activemq:artemis-jms-server to your application lets you use embedded mode.
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Artemis configuration is controlled by external configuration properties in spring.artemis.*
.
For example, you might declare the following section in application.properties
:
spring.artemis.mode=native
spring.artemis.host=192.168.1.210
spring.artemis.port=9876
spring.artemis.user=admin
spring.artemis.password=secret
When embedding the broker, you can choose if you want to enable persistence and list the destinations that should be made available.
These can be specified as a comma-separated list to create them with the default options, or you can define bean(s) of type org.apache.activemq.artemis.jms.server.config.JMSQueueConfiguration
or org.apache.activemq.artemis.jms.server.config.TopicConfiguration
, for advanced queue and topic configurations, respectively.
By default, a CachingConnectionFactory
wraps the native ConnectionFactory
with sensible settings that you can control by external configuration properties in spring.jms.*
:
spring.jms.cache.session-cache-size=5
If you’d rather use native pooling, you can do so by adding a dependency to org.messaginghub:pooled-jms
and configuring the JmsPoolConnectionFactory
accordingly, as shown in the following example:
spring.artemis.pool.enabled=true
spring.artemis.pool.max-connections=50
See ArtemisProperties
for more supported options.
No JNDI lookup is involved, and destinations are resolved against their names, using either the name
attribute in the Artemis configuration or the names provided through configuration.
13.1.3. Using a JNDI ConnectionFactory
If you are running your application in an application server, Spring Boot tries to locate a JMS ConnectionFactory
by using JNDI.
By default, the java:/JmsXA
and java:/XAConnectionFactory
location are checked.
You can use the spring.jms.jndi-name
property if you need to specify an alternative location, as shown in the following example:
spring.jms.jndi-name=java:/MyConnectionFactory
13.1.4. Sending a Message
Spring’s JmsTemplate
is auto-configured, and you can autowire it directly into your own beans, as shown in the following example:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final JmsTemplate jmsTemplate;
@Autowired
public MyBean(JmsTemplate jmsTemplate) {
this.jmsTemplate = jmsTemplate;
}
// ...
}
JmsMessagingTemplate can be injected in a similar manner.
If a DestinationResolver or a MessageConverter bean is defined, it is associated automatically to the auto-configured JmsTemplate .
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13.1.5. Receiving a Message
When the JMS infrastructure is present, any bean can be annotated with @JmsListener
to create a listener endpoint.
If no JmsListenerContainerFactory
has been defined, a default one is configured automatically.
If a DestinationResolver
or a MessageConverter
beans is defined, it is associated automatically to the default factory.
By default, the default factory is transactional.
If you run in an infrastructure where a JtaTransactionManager
is present, it is associated to the listener container by default.
If not, the sessionTransacted
flag is enabled.
In that latter scenario, you can associate your local data store transaction to the processing of an incoming message by adding @Transactional
on your listener method (or a delegate thereof).
This ensures that the incoming message is acknowledged, once the local transaction has completed.
This also includes sending response messages that have been performed on the same JMS session.
The following component creates a listener endpoint on the someQueue
destination:
@Component
public class MyBean {
@JmsListener(destination = "someQueue")
public void processMessage(String content) {
// ...
}
}
See the Javadoc of @EnableJms for more details.
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If you need to create more JmsListenerContainerFactory
instances or if you want to override the default, Spring Boot provides a DefaultJmsListenerContainerFactoryConfigurer
that you can use to initialize a DefaultJmsListenerContainerFactory
with the same settings as the one that is auto-configured.
For instance, the following example exposes another factory that uses a specific MessageConverter
:
@Configuration(proxyBeanMethods = false)
static class JmsConfiguration {
@Bean
public DefaultJmsListenerContainerFactory myFactory(
DefaultJmsListenerContainerFactoryConfigurer configurer) {
DefaultJmsListenerContainerFactory factory =
new DefaultJmsListenerContainerFactory();
configurer.configure(factory, connectionFactory());
factory.setMessageConverter(myMessageConverter());
return factory;
}
}
Then you can use the factory in any @JmsListener
-annotated method as follows:
@Component
public class MyBean {
@JmsListener(destination = "someQueue", containerFactory="myFactory")
public void processMessage(String content) {
// ...
}
}
13.2. AMQP
The Advanced Message Queuing Protocol (AMQP) is a platform-neutral, wire-level protocol for message-oriented middleware.
The Spring AMQP project applies core Spring concepts to the development of AMQP-based messaging solutions.
Spring Boot offers several conveniences for working with AMQP through RabbitMQ, including the spring-boot-starter-amqp
“Starter”.
13.2.1. RabbitMQ support
RabbitMQ is a lightweight, reliable, scalable, and portable message broker based on the AMQP protocol.
Spring uses RabbitMQ
to communicate through the AMQP protocol.
RabbitMQ configuration is controlled by external configuration properties in spring.rabbitmq.*
.
For example, you might declare the following section in application.properties
:
spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=admin
spring.rabbitmq.password=secret
Alternatively, you could configure the same connection using the addresses
attribute:
spring.rabbitmq.addresses=amqp://admin:secret@localhost
If a ConnectionNameStrategy
bean exists in the context, it will be automatically used to name connections created by the auto-configured ConnectionFactory
.
See RabbitProperties
for more of the supported options.
See Understanding AMQP, the protocol used by RabbitMQ for more details. |
13.2.2. Sending a Message
Spring’s AmqpTemplate
and AmqpAdmin
are auto-configured, and you can autowire them directly into your own beans, as shown in the following example:
import org.springframework.amqp.core.AmqpAdmin;
import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final AmqpAdmin amqpAdmin;
private final AmqpTemplate amqpTemplate;
@Autowired
public MyBean(AmqpAdmin amqpAdmin, AmqpTemplate amqpTemplate) {
this.amqpAdmin = amqpAdmin;
this.amqpTemplate = amqpTemplate;
}
// ...
}
RabbitMessagingTemplate can be injected in a similar manner.
If a MessageConverter bean is defined, it is associated automatically to the auto-configured AmqpTemplate .
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If necessary, any org.springframework.amqp.core.Queue
that is defined as a bean is automatically used to declare a corresponding queue on the RabbitMQ instance.
To retry operations, you can enable retries on the AmqpTemplate
(for example, in the event that the broker connection is lost):
spring.rabbitmq.template.retry.enabled=true
spring.rabbitmq.template.retry.initial-interval=2s
Retries are disabled by default.
You can also customize the RetryTemplate
programmatically by declaring a RabbitRetryTemplateCustomizer
bean.
If you need to create more RabbitTemplate
instances or if you want to override the default, Spring Boot provides a RabbitTemplateConfigurer
bean that you can use to initialize a RabbitTemplate
with the same settings as the factories used by the auto-configuration.
13.2.3. Receiving a Message
When the Rabbit infrastructure is present, any bean can be annotated with @RabbitListener
to create a listener endpoint.
If no RabbitListenerContainerFactory
has been defined, a default SimpleRabbitListenerContainerFactory
is automatically configured and you can switch to a direct container using the spring.rabbitmq.listener.type
property.
If a MessageConverter
or a MessageRecoverer
bean is defined, it is automatically associated with the default factory.
The following sample component creates a listener endpoint on the someQueue
queue:
@Component
public class MyBean {
@RabbitListener(queues = "someQueue")
public void processMessage(String content) {
// ...
}
}
See the Javadoc of @EnableRabbit for more details.
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If you need to create more RabbitListenerContainerFactory
instances or if you want to override the default, Spring Boot provides a SimpleRabbitListenerContainerFactoryConfigurer
and a DirectRabbitListenerContainerFactoryConfigurer
that you can use to initialize a SimpleRabbitListenerContainerFactory
and a DirectRabbitListenerContainerFactory
with the same settings as the factories used by the auto-configuration.
It does not matter which container type you chose. Those two beans are exposed by the auto-configuration. |
For instance, the following configuration class exposes another factory that uses a specific MessageConverter
:
@Configuration(proxyBeanMethods = false)
static class RabbitConfiguration {
@Bean
public SimpleRabbitListenerContainerFactory myFactory(
SimpleRabbitListenerContainerFactoryConfigurer configurer) {
SimpleRabbitListenerContainerFactory factory =
new SimpleRabbitListenerContainerFactory();
configurer.configure(factory, connectionFactory);
factory.setMessageConverter(myMessageConverter());
return factory;
}
}
Then you can use the factory in any @RabbitListener
-annotated method, as follows:
@Component
public class MyBean {
@RabbitListener(queues = "someQueue", containerFactory="myFactory")
public void processMessage(String content) {
// ...
}
}
You can enable retries to handle situations where your listener throws an exception.
By default, RejectAndDontRequeueRecoverer
is used, but you can define a MessageRecoverer
of your own.
When retries are exhausted, the message is rejected and either dropped or routed to a dead-letter exchange if the broker is configured to do so.
By default, retries are disabled.
You can also customize the RetryTemplate
programmatically by declaring a RabbitRetryTemplateCustomizer
bean.
By default, if retries are disabled and the listener throws an exception, the delivery is retried indefinitely.
You can modify this behavior in two ways: Set the defaultRequeueRejected property to false so that zero re-deliveries are attempted or throw an AmqpRejectAndDontRequeueException to signal the message should be rejected.
The latter is the mechanism used when retries are enabled and the maximum number of delivery attempts is reached.
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13.3. Apache Kafka Support
Apache Kafka is supported by providing auto-configuration of the spring-kafka
project.
Kafka configuration is controlled by external configuration properties in spring.kafka.*
.
For example, you might declare the following section in application.properties
:
spring.kafka.bootstrap-servers=localhost:9092
spring.kafka.consumer.group-id=myGroup
To create a topic on startup, add a bean of type NewTopic .
If the topic already exists, the bean is ignored.
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See KafkaProperties
for more supported options.
13.3.1. Sending a Message
Spring’s KafkaTemplate
is auto-configured, and you can autowire it directly in your own beans, as shown in the following example:
@Component
public class MyBean {
private final KafkaTemplate kafkaTemplate;
@Autowired
public MyBean(KafkaTemplate kafkaTemplate) {
this.kafkaTemplate = kafkaTemplate;
}
// ...
}
If the property spring.kafka.producer.transaction-id-prefix is defined, a KafkaTransactionManager is automatically configured.
Also, if a RecordMessageConverter bean is defined, it is automatically associated to the auto-configured KafkaTemplate .
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13.3.2. Receiving a Message
When the Apache Kafka infrastructure is present, any bean can be annotated with @KafkaListener
to create a listener endpoint.
If no KafkaListenerContainerFactory
has been defined, a default one is automatically configured with keys defined in spring.kafka.listener.*
.
The following component creates a listener endpoint on the someTopic
topic:
@Component
public class MyBean {
@KafkaListener(topics = "someTopic")
public void processMessage(String content) {
// ...
}
}
If a KafkaTransactionManager
bean is defined, it is automatically associated to the container factory.
Similarly, if a ErrorHandler
, AfterRollbackProcessor
or ConsumerAwareRebalanceListener
bean is defined, it is automatically associated to the default factory.
Depending on the listener type, a RecordMessageConverter
or BatchMessageConverter
bean is associated to the default factory.
If only a RecordMessageConverter
bean is present for a batch listener, it is wrapped in a BatchMessageConverter
.
A custom ChainedKafkaTransactionManager must be marked @Primary as it usually references the auto-configured KafkaTransactionManager bean.
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13.3.3. Kafka Streams
Spring for Apache Kafka provides a factory bean to create a StreamsBuilder
object and manage the lifecycle of its streams.
Spring Boot auto-configures the required KafkaStreamsConfiguration
bean as long as kafka-streams
is on the classpath and Kafka Streams is enabled via the @EnableKafkaStreams
annotation.
Enabling Kafka Streams means that the application id and bootstrap servers must be set.
The former can be configured using spring.kafka.streams.application-id
, defaulting to spring.application.name
if not set.
The latter can be set globally or specifically overridden just for streams.
Several additional properties are available using dedicated properties; other arbitrary Kafka properties can be set using the spring.kafka.streams.properties
namespace.
See also Additional Kafka Properties for more information.
To use the factory bean, simply wire StreamsBuilder
into your @Bean
as shown in the following example:
@Configuration(proxyBeanMethods = false)
@EnableKafkaStreams
public static class KafkaStreamsExampleConfiguration {
@Bean
public KStream<Integer, String> kStream(StreamsBuilder streamsBuilder) {
KStream<Integer, String> stream = streamsBuilder.stream("ks1In");
stream.map((k, v) -> new KeyValue<>(k, v.toUpperCase())).to("ks1Out",
Produced.with(Serdes.Integer(), new JsonSerde<>()));
return stream;
}
}
By default, the streams managed by the StreamBuilder
object it creates are started automatically.
You can customize this behaviour using the spring.kafka.streams.auto-startup
property.
13.3.4. Additional Kafka Properties
The properties supported by auto configuration are shown in appendix-application-properties.html. Note that, for the most part, these properties (hyphenated or camelCase) map directly to the Apache Kafka dotted properties. Refer to the Apache Kafka documentation for details.
The first few of these properties apply to all components (producers, consumers, admins, and streams) but can be specified at the component level if you wish to use different values. Apache Kafka designates properties with an importance of HIGH, MEDIUM, or LOW. Spring Boot auto-configuration supports all HIGH importance properties, some selected MEDIUM and LOW properties, and any properties that do not have a default value.
Only a subset of the properties supported by Kafka are available directly through the KafkaProperties
class.
If you wish to configure the producer or consumer with additional properties that are not directly supported, use the following properties:
spring.kafka.properties.prop.one=first
spring.kafka.admin.properties.prop.two=second
spring.kafka.consumer.properties.prop.three=third
spring.kafka.producer.properties.prop.four=fourth
spring.kafka.streams.properties.prop.five=fifth
This sets the common prop.one
Kafka property to first
(applies to producers, consumers and admins), the prop.two
admin property to second
, the prop.three
consumer property to third
, the prop.four
producer property to fourth
and the prop.five
streams property to fifth
.
You can also configure the Spring Kafka JsonDeserializer
as follows:
spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
spring.kafka.consumer.properties.spring.json.value.default.type=com.example.Invoice
spring.kafka.consumer.properties.spring.json.trusted.packages=com.example,org.acme
Similarly, you can disable the JsonSerializer
default behavior of sending type information in headers:
spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer
spring.kafka.producer.properties.spring.json.add.type.headers=false
Properties set in this way override any configuration item that Spring Boot explicitly supports. |
13.3.5. Testing with Embedded Kafka
Spring for Apache Kafka provides a convenient way to test projects with an embedded Apache Kafka broker.
To use this feature, annotate a test class with @EmbeddedKafka
from the spring-kafka-test
module.
For more information, please see the Spring for Apache Kafka reference manual.
To make Spring Boot auto-configuration work with the aforementioned embedded Apache Kafka broker, you need to remap a system property for embedded broker addresses (populated by the EmbeddedKafkaBroker
) into the Spring Boot configuration property for Apache Kafka.
There are several ways to do that:
-
Provide a system property to map embedded broker addresses into
spring.kafka.bootstrap-servers
in the test class:
static {
System.setProperty(EmbeddedKafkaBroker.BROKER_LIST_PROPERTY, "spring.kafka.bootstrap-servers");
}
-
Configure a property name on the
@EmbeddedKafka
annotation:
@EmbeddedKafka(topics = "someTopic",
bootstrapServersProperty = "spring.kafka.bootstrap-servers")
-
Use a placeholder in configuration properties:
spring.kafka.bootstrap-servers=${spring.embedded.kafka.brokers}
14. Calling REST Services with RestTemplate
If you need to call remote REST services from your application, you can use the Spring Framework’s RestTemplate
class.
Since RestTemplate
instances often need to be customized before being used, Spring Boot does not provide any single auto-configured RestTemplate
bean.
It does, however, auto-configure a RestTemplateBuilder
, which can be used to create RestTemplate
instances when needed.
The auto-configured RestTemplateBuilder
ensures that sensible HttpMessageConverters
are applied to RestTemplate
instances.
The following code shows a typical example:
@Service
public class MyService {
private final RestTemplate restTemplate;
public MyService(RestTemplateBuilder restTemplateBuilder) {
this.restTemplate = restTemplateBuilder.build();
}
public Details someRestCall(String name) {
return this.restTemplate.getForObject("/{name}/details", Details.class, name);
}
}
RestTemplateBuilder includes a number of useful methods that can be used to quickly configure a RestTemplate .
For example, to add BASIC auth support, you can use builder.basicAuthentication("user", "password").build() .
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14.1. RestTemplate Customization
There are three main approaches to RestTemplate
customization, depending on how broadly you want the customizations to apply.
To make the scope of any customizations as narrow as possible, inject the auto-configured RestTemplateBuilder
and then call its methods as required.
Each method call returns a new RestTemplateBuilder
instance, so the customizations only affect this use of the builder.
To make an application-wide, additive customization, use a RestTemplateCustomizer
bean.
All such beans are automatically registered with the auto-configured RestTemplateBuilder
and are applied to any templates that are built with it.
The following example shows a customizer that configures the use of a proxy for all hosts except 192.168.0.5
:
static class ProxyCustomizer implements RestTemplateCustomizer {
@Override
public void customize(RestTemplate restTemplate) {
HttpHost proxy = new HttpHost("proxy.example.com");
HttpClient httpClient = HttpClientBuilder.create().setRoutePlanner(new DefaultProxyRoutePlanner(proxy) {
@Override
public HttpHost determineProxy(HttpHost target, HttpRequest request, HttpContext context)
throws HttpException {
if (target.getHostName().equals("192.168.0.5")) {
return null;
}
return super.determineProxy(target, request, context);
}
}).build();
restTemplate.setRequestFactory(new HttpComponentsClientHttpRequestFactory(httpClient));
}
}
Finally, the most extreme (and rarely used) option is to create your own RestTemplateBuilder
bean.
Doing so switches off the auto-configuration of a RestTemplateBuilder
and prevents any RestTemplateCustomizer
beans from being used.
15. Calling REST Services with WebClient
If you have Spring WebFlux on your classpath, you can also choose to use WebClient
to call remote REST services.
Compared to RestTemplate
, this client has a more functional feel and is fully reactive.
You can learn more about the WebClient
in the dedicated section in the Spring Framework docs.
Spring Boot creates and pre-configures a WebClient.Builder
for you; it is strongly advised to inject it in your components and use it to create WebClient
instances.
Spring Boot is configuring that builder to share HTTP resources, reflect codecs setup in the same fashion as the server ones (see WebFlux HTTP codecs auto-configuration), and more.
The following code shows a typical example:
@Service
public class MyService {
private final WebClient webClient;
public MyService(WebClient.Builder webClientBuilder) {
this.webClient = webClientBuilder.baseUrl("https://example.org").build();
}
public Mono<Details> someRestCall(String name) {
return this.webClient.get().uri("/{name}/details", name)
.retrieve().bodyToMono(Details.class);
}
}
15.1. WebClient Runtime
Spring Boot will auto-detect which ClientHttpConnector
to use to drive WebClient
, depending on the libraries available on the application classpath.
For now, Reactor Netty and Jetty RS client are supported.
The spring-boot-starter-webflux
starter depends on io.projectreactor.netty:reactor-netty
by default, which brings both server and client implementations.
If you choose to use Jetty as a reactive server instead, you should add a dependency on the Jetty Reactive HTTP client library, org.eclipse.jetty:jetty-reactive-httpclient
.
Using the same technology for server and client has it advantages, as it will automatically share HTTP resources between client and server.
Developers can override the resource configuration for Jetty and Reactor Netty by providing a custom ReactorResourceFactory
or JettyResourceFactory
bean - this will be applied to both clients and servers.
If you wish to override that choice for the client, you can define your own ClientHttpConnector
bean and have full control over the client configuration.
You can learn more about the WebClient
configuration options in the Spring Framework reference documentation.
15.2. WebClient Customization
There are three main approaches to WebClient
customization, depending on how broadly you want the customizations to apply.
To make the scope of any customizations as narrow as possible, inject the auto-configured WebClient.Builder
and then call its methods as required.
WebClient.Builder
instances are stateful: Any change on the builder is reflected in all clients subsequently created with it.
If you want to create several clients with the same builder, you can also consider cloning the builder with WebClient.Builder other = builder.clone();
.
To make an application-wide, additive customization to all WebClient.Builder
instances, you can declare WebClientCustomizer
beans and change the WebClient.Builder
locally at the point of injection.
Finally, you can fall back to the original API and use WebClient.create()
.
In that case, no auto-configuration or WebClientCustomizer
is applied.
16. Validation
The method validation feature supported by Bean Validation 1.1 is automatically enabled as long as a JSR-303 implementation (such as Hibernate validator) is on the classpath.
This lets bean methods be annotated with javax.validation
constraints on their parameters and/or on their return value.
Target classes with such annotated methods need to be annotated with the @Validated
annotation at the type level for their methods to be searched for inline constraint annotations.
For instance, the following service triggers the validation of the first argument, making sure its size is between 8 and 10:
@Service
@Validated
public class MyBean {
public Archive findByCodeAndAuthor(@Size(min = 8, max = 10) String code,
Author author) {
...
}
}
17. Sending Email
The Spring Framework provides an easy abstraction for sending email by using the JavaMailSender
interface, and Spring Boot provides auto-configuration for it as well as a starter module.
See the reference documentation for a detailed explanation of how you can use JavaMailSender .
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If spring.mail.host
and the relevant libraries (as defined by spring-boot-starter-mail
) are available, a default JavaMailSender
is created if none exists.
The sender can be further customized by configuration items from the spring.mail
namespace.
See MailProperties
for more details.
In particular, certain default timeout values are infinite, and you may want to change that to avoid having a thread blocked by an unresponsive mail server, as shown in the following example:
spring.mail.properties.mail.smtp.connectiontimeout=5000
spring.mail.properties.mail.smtp.timeout=3000
spring.mail.properties.mail.smtp.writetimeout=5000
It is also possible to configure a JavaMailSender
with an existing Session
from JNDI:
spring.mail.jndi-name=mail/Session
When a jndi-name
is set, it takes precedence over all other Session-related settings.
18. Distributed Transactions with JTA
Spring Boot supports distributed JTA transactions across multiple XA resources by using either an Atomikos or Bitronix embedded transaction manager. JTA transactions are also supported when deploying to a suitable Java EE Application Server.
When a JTA environment is detected, Spring’s JtaTransactionManager
is used to manage transactions.
Auto-configured JMS, DataSource, and JPA beans are upgraded to support XA transactions.
You can use standard Spring idioms, such as @Transactional
, to participate in a distributed transaction.
If you are within a JTA environment and still want to use local transactions, you can set the spring.jta.enabled
property to false
to disable the JTA auto-configuration.
18.1. Using an Atomikos Transaction Manager
Atomikos is a popular open source transaction manager which can be embedded into your Spring Boot application.
You can use the spring-boot-starter-jta-atomikos
starter to pull in the appropriate Atomikos libraries.
Spring Boot auto-configures Atomikos and ensures that appropriate depends-on
settings are applied to your Spring beans for correct startup and shutdown ordering.
By default, Atomikos transaction logs are written to a transaction-logs
directory in your application’s home directory (the directory in which your application jar file resides).
You can customize the location of this directory by setting a spring.jta.log-dir
property in your application.properties
file.
Properties starting with spring.jta.atomikos.properties
can also be used to customize the Atomikos UserTransactionServiceImp
.
See the AtomikosProperties
Javadoc for complete details.
To ensure that multiple transaction managers can safely coordinate the same resource managers, each Atomikos instance must be configured with a unique ID.
By default, this ID is the IP address of the machine on which Atomikos is running.
To ensure uniqueness in production, you should configure the spring.jta.transaction-manager-id property with a different value for each instance of your application.
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18.2. Using a Bitronix Transaction Manager
Bitronix is a popular open-source JTA transaction manager implementation.
You can use the spring-boot-starter-jta-bitronix
starter to add the appropriate Bitronix dependencies to your project.
As with Atomikos, Spring Boot automatically configures Bitronix and post-processes your beans to ensure that startup and shutdown ordering is correct.
By default, Bitronix transaction log files (part1.btm
and part2.btm
) are written to a transaction-logs
directory in your application home directory.
You can customize the location of this directory by setting the spring.jta.log-dir
property.
Properties starting with spring.jta.bitronix.properties
are also bound to the bitronix.tm.Configuration
bean, allowing for complete customization.
See the Bitronix documentation for details.
To ensure that multiple transaction managers can safely coordinate the same resource managers, each Bitronix instance must be configured with a unique ID.
By default, this ID is the IP address of the machine on which Bitronix is running.
To ensure uniqueness in production, you should configure the spring.jta.transaction-manager-id property with a different value for each instance of your application.
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18.3. Using a Java EE Managed Transaction Manager
If you package your Spring Boot application as a war
or ear
file and deploy it to a Java EE application server, you can use your application server’s built-in transaction manager.
Spring Boot tries to auto-configure a transaction manager by looking at common JNDI locations (java:comp/UserTransaction
, java:comp/TransactionManager
, and so on).
If you use a transaction service provided by your application server, you generally also want to ensure that all resources are managed by the server and exposed over JNDI.
Spring Boot tries to auto-configure JMS by looking for a ConnectionFactory
at the JNDI path (java:/JmsXA
or java:/XAConnectionFactory
), and you can use the spring.datasource.jndi-name
property to configure your DataSource
.
18.4. Mixing XA and Non-XA JMS Connections
When using JTA, the primary JMS ConnectionFactory
bean is XA-aware and participates in distributed transactions.
In some situations, you might want to process certain JMS messages by using a non-XA ConnectionFactory
.
For example, your JMS processing logic might take longer than the XA timeout.
If you want to use a non-XA ConnectionFactory
, you can inject the nonXaJmsConnectionFactory
bean rather than the @Primary
jmsConnectionFactory
bean.
For consistency, the jmsConnectionFactory
bean is also provided by using the bean alias xaJmsConnectionFactory
.
The following example shows how to inject ConnectionFactory
instances:
// Inject the primary (XA aware) ConnectionFactory
@Autowired
private ConnectionFactory defaultConnectionFactory;
// Inject the XA aware ConnectionFactory (uses the alias and injects the same as above)
@Autowired
@Qualifier("xaJmsConnectionFactory")
private ConnectionFactory xaConnectionFactory;
// Inject the non-XA aware ConnectionFactory
@Autowired
@Qualifier("nonXaJmsConnectionFactory")
private ConnectionFactory nonXaConnectionFactory;
18.5. Supporting an Alternative Embedded Transaction Manager
The XAConnectionFactoryWrapper
and XADataSourceWrapper
interfaces can be used to support alternative embedded transaction managers.
The interfaces are responsible for wrapping XAConnectionFactory
and XADataSource
beans and exposing them as regular ConnectionFactory
and DataSource
beans, which transparently enroll in the distributed transaction.
DataSource and JMS auto-configuration use JTA variants, provided you have a JtaTransactionManager
bean and appropriate XA wrapper beans registered within your ApplicationContext
.
The BitronixXAConnectionFactoryWrapper and BitronixXADataSourceWrapper provide good examples of how to write XA wrappers.
19. Hazelcast
If Hazelcast is on the classpath and a suitable configuration is found, Spring Boot auto-configures a HazelcastInstance
that you can inject in your application.
If you define a com.hazelcast.config.Config
bean, Spring Boot uses that.
If your configuration defines an instance name, Spring Boot tries to locate an existing instance rather than creating a new one.
You could also specify the Hazelcast configuration file to use through configuration, as shown in the following example:
spring.hazelcast.config=classpath:config/my-hazelcast.xml
Otherwise, Spring Boot tries to find the Hazelcast configuration from the default locations: hazelcast.xml
in the working directory or at the root of the classpath, or a .yaml
counterpart in the same locations.
We also check if the hazelcast.config
system property is set.
See the Hazelcast documentation for more details.
If hazelcast-client
is present on the classpath, Spring Boot first attempts to create a client by checking the following configuration options:
-
The presence of a
com.hazelcast.client.config.ClientConfig
bean. -
A configuration file defined by the
spring.hazelcast.config
property. -
The presence of the
hazelcast.client.config
system property. -
A
hazelcast-client.xml
in the working directory or at the root of the classpath. -
A
hazelcast-client.yaml
in the working directory or at the root of the classpath.
Spring Boot also has explicit caching support for Hazelcast.
If caching is enabled, the HazelcastInstance is automatically wrapped in a CacheManager implementation.
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20. Quartz Scheduler
Spring Boot offers several conveniences for working with the Quartz scheduler, including the spring-boot-starter-quartz
“Starter”.
If Quartz is available, a Scheduler
is auto-configured (through the SchedulerFactoryBean
abstraction).
Beans of the following types are automatically picked up and associated with the Scheduler
:
-
JobDetail
: defines a particular Job.JobDetail
instances can be built with theJobBuilder
API. -
Calendar
. -
Trigger
: defines when a particular job is triggered.
By default, an in-memory JobStore
is used.
However, it is possible to configure a JDBC-based store if a DataSource
bean is available in your application and if the spring.quartz.job-store-type
property is configured accordingly, as shown in the following example:
spring.quartz.job-store-type=jdbc
When the JDBC store is used, the schema can be initialized on startup, as shown in the following example:
spring.quartz.jdbc.initialize-schema=always
By default, the database is detected and initialized by using the standard scripts provided with the Quartz library.
These scripts drop existing tables, deleting all triggers on every restart.
It is also possible to provide a custom script by setting the spring.quartz.jdbc.schema property.
|
To have Quartz use a DataSource
other than the application’s main DataSource
, declare a DataSource
bean, annotating its @Bean
method with @QuartzDataSource
.
Doing so ensures that the Quartz-specific DataSource
is used by both the SchedulerFactoryBean
and for schema initialization.
By default, jobs created by configuration will not overwrite already registered jobs that have been read from a persistent job store.
To enable overwriting existing job definitions set the spring.quartz.overwrite-existing-jobs
property.
Quartz Scheduler configuration can be customized using spring.quartz
properties and SchedulerFactoryBeanCustomizer
beans, which allow programmatic SchedulerFactoryBean
customization.
Advanced Quartz configuration properties can be customized using spring.quartz.properties.*
.
In particular, an Executor bean is not associated with the scheduler as Quartz offers a way to configure the scheduler via spring.quartz.properties .
If you need to customize the task executor, consider implementing SchedulerFactoryBeanCustomizer .
|
Jobs can define setters to inject data map properties. Regular beans can also be injected in a similar manner, as shown in the following example:
public class SampleJob extends QuartzJobBean {
private MyService myService;
private String name;
// Inject "MyService" bean
public void setMyService(MyService myService) { ... }
// Inject the "name" job data property
public void setName(String name) { ... }
@Override
protected void executeInternal(JobExecutionContext context)
throws JobExecutionException {
...
}
}
21. Task Execution and Scheduling
In the absence of an Executor
bean in the context, Spring Boot auto-configures a ThreadPoolTaskExecutor
with sensible defaults that can be automatically associated to asynchronous task execution (@EnableAsync
) and Spring MVC asynchronous request processing.
If you have defined a custom The auto-configured |
The thread pool uses 8 core threads that can grow and shrink according to the load.
Those default settings can be fine-tuned using the spring.task.execution
namespace as shown in the following example:
spring.task.execution.pool.max-size=16
spring.task.execution.pool.queue-capacity=100
spring.task.execution.pool.keep-alive=10s
This changes the thread pool to use a bounded queue so that when the queue is full (100 tasks), the thread pool increases to maximum 16 threads. Shrinking of the pool is more aggressive as threads are reclaimed when they are idle for 10 seconds (rather than 60 seconds by default).
A ThreadPoolTaskScheduler
can also be auto-configured if need to be associated to scheduled task execution (@EnableScheduling
).
The thread pool uses one thread by default and those settings can be fine-tuned using the spring.task.scheduling
namespace.
Both a TaskExecutorBuilder
bean and a TaskSchedulerBuilder
bean are made available in the context if a custom executor or scheduler needs to be created.
22. Spring Integration
Spring Boot offers several conveniences for working with Spring Integration, including the spring-boot-starter-integration
“Starter”.
Spring Integration provides abstractions over messaging and also other transports such as HTTP, TCP, and others.
If Spring Integration is available on your classpath, it is initialized through the @EnableIntegration
annotation.
Spring Boot also configures some features that are triggered by the presence of additional Spring Integration modules.
If spring-integration-jmx
is also on the classpath, message processing statistics are published over JMX.
If spring-integration-jdbc
is available, the default database schema can be created on startup, as shown in the following line:
spring.integration.jdbc.initialize-schema=always
See the IntegrationAutoConfiguration
and IntegrationProperties
classes for more details.
By default, if a Micrometer meterRegistry
bean is present, Spring Integration metrics will be managed by Micrometer.
If you wish to use legacy Spring Integration metrics, add a DefaultMetricsFactory
bean to the application context.
23. Spring Session
Spring Boot provides Spring Session auto-configuration for a wide range of data stores. When building a Servlet web application, the following stores can be auto-configured:
-
JDBC
-
Redis
-
Hazelcast
-
MongoDB
When building a reactive web application, the following stores can be auto-configured:
-
Redis
-
MongoDB
If a single Spring Session module is present on the classpath, Spring Boot uses that store implementation automatically.
If you have more than one implementation, you must choose the StoreType
that you wish to use to store the sessions.
For instance, to use JDBC as the back-end store, you can configure your application as follows:
spring.session.store-type=jdbc
You can disable Spring Session by setting the store-type to none .
|
Each store has specific additional settings. For instance, it is possible to customize the name of the table for the JDBC store, as shown in the following example:
spring.session.jdbc.table-name=SESSIONS
For setting the timeout of the session you can use the spring.session.timeout
property.
If that property is not set, the auto-configuration falls back to the value of server.servlet.session.timeout
.
24. Monitoring and Management over JMX
Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications.
Spring Boot exposes the most suitable MBeanServer
as a bean with an ID of mbeanServer
.
Any of your beans that are annotated with Spring JMX annotations (@ManagedResource
, @ManagedAttribute
, or @ManagedOperation
) are exposed to it.
If your platform provides a standard MBeanServer
, Spring Boot will use that and default to the VM MBeanServer
if necessary.
If all that fails, a new MBeanServer
will be created.
See the JmxAutoConfiguration
class for more details.
25. Testing
Spring Boot provides a number of utilities and annotations to help when testing your application.
Test support is provided by two modules: spring-boot-test
contains core items, and spring-boot-test-autoconfigure
supports auto-configuration for tests.
Most developers use the spring-boot-starter-test
“Starter”, which imports both Spring Boot test modules as well as JUnit Jupiter, AssertJ, Hamcrest, and a number of other useful libraries.
The starter also brings the vintage engine so that you can run both JUnit 4 and JUnit 5 tests. If you have migrated your tests to JUnit 5, you should exclude JUnit 4 support, as shown in the following example:
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25.1. Test Scope Dependencies
The spring-boot-starter-test
“Starter” (in the test
scope
) contains the following provided libraries:
-
JUnit 5 (including the vintage engine for backward compatibility with JUnit 4): The de-facto standard for unit testing Java applications.
-
Spring Test & Spring Boot Test: Utilities and integration test support for Spring Boot applications.
-
AssertJ: A fluent assertion library.
-
Hamcrest: A library of matcher objects (also known as constraints or predicates).
-
Mockito: A Java mocking framework.
-
JSONassert: An assertion library for JSON.
-
JsonPath: XPath for JSON.
We generally find these common libraries to be useful when writing tests. If these libraries do not suit your needs, you can add additional test dependencies of your own.
25.2. Testing Spring Applications
One of the major advantages of dependency injection is that it should make your code easier to unit test.
You can instantiate objects by using the new
operator without even involving Spring.
You can also use mock objects instead of real dependencies.
Often, you need to move beyond unit testing and start integration testing (with a Spring ApplicationContext
).
It is useful to be able to perform integration testing without requiring deployment of your application or needing to connect to other infrastructure.
The Spring Framework includes a dedicated test module for such integration testing.
You can declare a dependency directly to org.springframework:spring-test
or use the spring-boot-starter-test
“Starter” to pull it in transitively.
If you have not used the spring-test
module before, you should start by reading the relevant section of the Spring Framework reference documentation.
25.3. Testing Spring Boot Applications
A Spring Boot application is a Spring ApplicationContext
, so nothing very special has to be done to test it beyond what you would normally do with a vanilla Spring context.
External properties, logging, and other features of Spring Boot are installed in the context by default only if you use SpringApplication to create it.
|
Spring Boot provides a @SpringBootTest
annotation, which can be used as an alternative to the standard spring-test
@ContextConfiguration
annotation when you need Spring Boot features.
The annotation works by creating the ApplicationContext
used in your tests through SpringApplication
.
In addition to @SpringBootTest
a number of other annotations are also provided for testing more specific slices of an application.
If you are using JUnit 4, don’t forget to also add @RunWith(SpringRunner.class) to your test, otherwise the annotations will be ignored.
If you are using JUnit 5, there’s no need to add the equivalent @ExtendWith(SpringExtension.class) as @SpringBootTest and the other @…Test annotations are already annotated with it.
|
By default, @SpringBootTest
will not start a server.
You can use the webEnvironment
attribute of @SpringBootTest
to further refine how your tests run:
-
MOCK
(Default) : Loads a webApplicationContext
and provides a mock web environment. Embedded servers are not started when using this annotation. If a web environment is not available on your classpath, this mode transparently falls back to creating a regular non-webApplicationContext
. It can be used in conjunction with@AutoConfigureMockMvc
or@AutoConfigureWebTestClient
for mock-based testing of your web application. -
RANDOM_PORT
: Loads aWebServerApplicationContext
and provides a real web environment. Embedded servers are started and listen on a random port. -
DEFINED_PORT
: Loads aWebServerApplicationContext
and provides a real web environment. Embedded servers are started and listen on a defined port (from yourapplication.properties
) or on the default port of8080
. -
NONE
: Loads anApplicationContext
by usingSpringApplication
but does not provide any web environment (mock or otherwise).
If your test is @Transactional , it rolls back the transaction at the end of each test method by default.
However, as using this arrangement with either RANDOM_PORT or DEFINED_PORT implicitly provides a real servlet environment, the HTTP client and server run in separate threads and, thus, in separate transactions.
Any transaction initiated on the server does not roll back in this case.
|
@SpringBootTest with webEnvironment = WebEnvironment.RANDOM_PORT will also start the management server on a separate random port if your application uses a different port for the management server.
|
25.3.1. Detecting Web Application Type
If Spring MVC is available, a regular MVC-based application context is configured. If you have only Spring WebFlux, we’ll detect that and configure a WebFlux-based application context instead.
If both are present, Spring MVC takes precedence.
If you want to test a reactive web application in this scenario, you must set the spring.main.web-application-type
property:
@SpringBootTest(properties = "spring.main.web-application-type=reactive")
class MyWebFluxTests { ... }
25.3.2. Detecting Test Configuration
If you are familiar with the Spring Test Framework, you may be used to using @ContextConfiguration(classes=…)
in order to specify which Spring @Configuration
to load.
Alternatively, you might have often used nested @Configuration
classes within your test.
When testing Spring Boot applications, this is often not required.
Spring Boot’s @*Test
annotations search for your primary configuration automatically whenever you do not explicitly define one.
The search algorithm works up from the package that contains the test until it finds a class annotated with @SpringBootApplication
or @SpringBootConfiguration
.
As long as you structured your code in a sensible way, your main configuration is usually found.
If you use a test annotation to test a more specific slice of your application, you should avoid adding configuration settings that are specific to a particular area on the main method’s application class. The underlying component scan configuration of |
If you want to customize the primary configuration, you can use a nested @TestConfiguration
class.
Unlike a nested @Configuration
class, which would be used instead of your application’s primary configuration, a nested @TestConfiguration
class is used in addition to your application’s primary configuration.
Spring’s test framework caches application contexts between tests. Therefore, as long as your tests share the same configuration (no matter how it is discovered), the potentially time-consuming process of loading the context happens only once. |
25.3.3. Excluding Test Configuration
If your application uses component scanning (for example, if you use @SpringBootApplication
or @ComponentScan
), you may find top-level configuration classes that you created only for specific tests accidentally get picked up everywhere.
As we have seen earlier, @TestConfiguration
can be used on an inner class of a test to customize the primary configuration.
When placed on a top-level class, @TestConfiguration
indicates that classes in src/test/java
should not be picked up by scanning.
You can then import that class explicitly where it is required, as shown in the following example:
@SpringBootTest
@Import(MyTestsConfiguration.class)
class MyTests {
@Test
void exampleTest() {
...
}
}
If you directly use @ComponentScan (that is, not through @SpringBootApplication ) you need to register the TypeExcludeFilter with it.
See the Javadoc for details.
|
25.3.4. Using Application Arguments
If your application expects arguments, you can
have @SpringBootTest
inject them using the args
attribute.
@SpringBootTest(args = "--app.test=one")
class ApplicationArgumentsExampleTests {
@Test
void applicationArgumentsPopulated(@Autowired ApplicationArguments args) {
assertThat(args.getOptionNames()).containsOnly("app.test");
assertThat(args.getOptionValues("app.test")).containsOnly("one");
}
}
25.3.5. Testing with a mock environment
By default, @SpringBootTest
does not start the server.
If you have web endpoints that you want to test against this mock environment, you can additionally configure MockMvc
as shown in the following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
@SpringBootTest
@AutoConfigureMockMvc
class MockMvcExampleTests {
@Test
void exampleTest(@Autowired MockMvc mvc) throws Exception {
mvc.perform(get("/")).andExpect(status().isOk()).andExpect(content().string("Hello World"));
}
}
If you want to focus only on the web layer and not start a complete ApplicationContext , consider using @WebMvcTest instead.
|
Alternatively, you can configure a WebTestClient
as shown in the following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.AutoConfigureWebTestClient;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.web.reactive.server.WebTestClient;
@SpringBootTest
@AutoConfigureWebTestClient
class MockWebTestClientExampleTests {
@Test
void exampleTest(@Autowired WebTestClient webClient) {
webClient.get().uri("/").exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("Hello World");
}
}
Testing within a mocked environment is usually faster than running with a full Servlet container. However, since mocking occurs at the Spring MVC layer, code that relies on lower-level Servlet container behavior cannot be directly tested with MockMvc. For example, Spring Boot’s error handling is based on the “error page” support provided by the Servlet container. This means that, whilst you can test your MVC layer throws and handles exceptions as expected, you cannot directly test that a specific custom error page is rendered. If you need to test these lower-level concerns, you can start a fully running server as described in the next section. |
25.3.6. Testing with a running server
If you need to start a full running server, we recommend that you use random ports.
If you use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT)
, an available port is picked at random each time your test runs.
The @LocalServerPort
annotation can be used to inject the actual port used into your test.
For convenience, tests that need to make REST calls to the started server can additionally @Autowire
a WebTestClient
, which resolves relative links to the running server and comes with a dedicated API for verifying responses, as shown in the following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.test.web.reactive.server.WebTestClient;
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class RandomPortWebTestClientExampleTests {
@Test
void exampleTest(@Autowired WebTestClient webClient) {
webClient.get().uri("/").exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("Hello World");
}
}
This setup requires spring-webflux
on the classpath.
If you can’t or won’t add webflux, Spring Boot also provides a TestRestTemplate
facility:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.test.web.client.TestRestTemplate;
import static org.assertj.core.api.Assertions.assertThat;
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class RandomPortTestRestTemplateExampleTests {
@Test
void exampleTest(@Autowired TestRestTemplate restTemplate) {
String body = restTemplate.getForObject("/", String.class);
assertThat(body).isEqualTo("Hello World");
}
}
25.3.7. Customizing WebTestClient
To customize the WebTestClient
bean, configure a WebTestClientBuilderCustomizer
bean.
Any such beans are called with the WebTestClient.Builder
that is used to create the WebTestClient
.
25.3.8. Using JMX
As the test context framework caches context, JMX is disabled by default to prevent identical components to register on the same domain.
If such test needs access to an MBeanServer
, consider marking it dirty as well:
@ExtendWith(SpringExtension.class)
@SpringBootTest(properties = "spring.jmx.enabled=true")
@DirtiesContext
class SampleJmxTests {
@Autowired
private MBeanServer mBeanServer;
@Test
void exampleTest() {
// ...
}
}
25.3.9. Mocking and Spying Beans
When running tests, it is sometimes necessary to mock certain components within your application context. For example, you may have a facade over some remote service that is unavailable during development. Mocking can also be useful when you want to simulate failures that might be hard to trigger in a real environment.
Spring Boot includes a @MockBean
annotation that can be used to define a Mockito mock for a bean inside your ApplicationContext
.
You can use the annotation to add new beans or replace a single existing bean definition.
The annotation can be used directly on test classes, on fields within your test, or on @Configuration
classes and fields.
When used on a field, the instance of the created mock is also injected.
Mock beans are automatically reset after each test method.
If your test uses one of Spring Boot’s test annotations (such as
|
The following example replaces an existing RemoteService
bean with a mock implementation:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.mock.mockito.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
@SpringBootTest
class MyTests {
@MockBean
private RemoteService remoteService;
@Autowired
private Reverser reverser;
@Test
void exampleTest() {
// RemoteService has been injected into the reverser bean
given(this.remoteService.someCall()).willReturn("mock");
String reverse = reverser.reverseSomeCall();
assertThat(reverse).isEqualTo("kcom");
}
}
@MockBean cannot be used to mock the behavior of a bean that’s exercised during application context refresh.
By the time the test is executed, the application context refresh has completed and it is too late to configure the mocked behavior.
We recommend using a @Bean method to create and configure the mock in this situation.
|
Additionally, you can use @SpyBean
to wrap any existing bean with a Mockito spy
.
See the Javadoc for full details.
CGLib proxies, such as those created for scoped beans, declare the proxied methods as final .
This stops Mockito from functioning correctly as it cannot mock or spy on final methods in its default configuration.
If you want to mock or spy on such a bean, configure Mockito to use its inline mock maker by adding org.mockito:mockito-inline to your application’s test dependencies.
This allows Mockito to mock and spy on final methods.
|
While Spring’s test framework caches application contexts between tests and reuses a context for tests sharing the same configuration, the use of @MockBean or @SpyBean influences the cache key, which will most likely increase the number of contexts.
|
If you are using @SpyBean to spy on a bean with @Cacheable methods that refer to parameters by name, your application must be compiled with -parameters .
This ensures that the parameter names are available to the caching infrastructure once the bean has been spied upon.
|
25.3.10. Auto-configured Tests
Spring Boot’s auto-configuration system works well for applications but can sometimes be a little too much for tests. It often helps to load only the parts of the configuration that are required to test a “slice” of your application. For example, you might want to test that Spring MVC controllers are mapping URLs correctly, and you do not want to involve database calls in those tests, or you might want to test JPA entities, and you are not interested in the web layer when those tests run.
The spring-boot-test-autoconfigure
module includes a number of annotations that can be used to automatically configure such “slices”.
Each of them works in a similar way, providing a @…Test
annotation that loads the ApplicationContext
and one or more @AutoConfigure…
annotations that can be used to customize auto-configuration settings.
Each slice restricts component scan to appropriate components and loads a very restricted set of auto-configuration classes.
If you need to exclude one of them, most @…Test annotations provide an excludeAutoConfiguration attribute.
Alternatively, you can use @ImportAutoConfiguration#exclude .
|
Including multiple “slices” by using several @…Test annotations in one test is not supported.
If you need multiple “slices”, pick one of the @…Test annotations and include the @AutoConfigure… annotations of the other “slices” by hand.
|
It is also possible to use the @AutoConfigure… annotations with the standard @SpringBootTest annotation.
You can use this combination if you are not interested in “slicing” your application but you want some of the auto-configured test beans.
|
25.3.11. Auto-configured JSON Tests
To test that object JSON serialization and deserialization is working as expected, you can use the @JsonTest
annotation.
@JsonTest
auto-configures the available supported JSON mapper, which can be one of the following libraries:
-
Jackson
ObjectMapper
, any@JsonComponent
beans and any JacksonModule
s -
Gson
-
Jsonb
A list of the auto-configurations that are enabled by @JsonTest can be found in the appendix.
|
If you need to configure elements of the auto-configuration, you can use the @AutoConfigureJsonTesters
annotation.
Spring Boot includes AssertJ-based helpers that work with the JSONAssert and JsonPath libraries to check that JSON appears as expected.
The JacksonTester
, GsonTester
, JsonbTester
, and BasicJsonTester
classes can be used for Jackson, Gson, Jsonb, and Strings respectively.
Any helper fields on the test class can be @Autowired
when using @JsonTest
.
The following example shows a test class for Jackson:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.json.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.json.*;
import static org.assertj.core.api.Assertions.*;
@JsonTest
class MyJsonTests {
@Autowired
private JacksonTester<VehicleDetails> json;
@Test
void testSerialize() throws Exception {
VehicleDetails details = new VehicleDetails("Honda", "Civic");
// Assert against a `.json` file in the same package as the test
assertThat(this.json.write(details)).isEqualToJson("expected.json");
// Or use JSON path based assertions
assertThat(this.json.write(details)).hasJsonPathStringValue("@.make");
assertThat(this.json.write(details)).extractingJsonPathStringValue("@.make")
.isEqualTo("Honda");
}
@Test
void testDeserialize() throws Exception {
String content = "{\"make\":\"Ford\",\"model\":\"Focus\"}";
assertThat(this.json.parse(content))
.isEqualTo(new VehicleDetails("Ford", "Focus"));
assertThat(this.json.parseObject(content).getMake()).isEqualTo("Ford");
}
}
JSON helper classes can also be used directly in standard unit tests.
To do so, call the initFields method of the helper in your @Before method if you do not use @JsonTest .
|
If you’re using Spring Boot’s AssertJ-based helpers to assert on a number value at a given JSON path, you might not be able to use isEqualTo
depending on the type.
Instead, you can use AssertJ’s satisfies
to assert that the value matches the given condition.
For instance, the following example asserts that the actual number is a float value close to 0.15
within an offset of 0.01
.
assertThat(json.write(message))
.extractingJsonPathNumberValue("@.test.numberValue")
.satisfies((number) -> assertThat(number.floatValue()).isCloseTo(0.15f, within(0.01f)));
25.3.12. Auto-configured Spring MVC Tests
To test whether Spring MVC controllers are working as expected, use the @WebMvcTest
annotation.
@WebMvcTest
auto-configures the Spring MVC infrastructure and limits scanned beans to @Controller
, @ControllerAdvice
, @JsonComponent
, Converter
, GenericConverter
, Filter
, HandlerInterceptor
, WebMvcConfigurer
, and HandlerMethodArgumentResolver
.
Regular @Component
beans are not scanned when using this annotation.
A list of the auto-configuration settings that are enabled by @WebMvcTest can be found in the appendix.
|
If you need to register extra components, such as the Jackson Module , you can import additional configuration classes by using @Import on your test.
|
Often, @WebMvcTest
is limited to a single controller and is used in combination with @MockBean
to provide mock implementations for required collaborators.
@WebMvcTest
also auto-configures MockMvc
.
Mock MVC offers a powerful way to quickly test MVC controllers without needing to start a full HTTP server.
You can also auto-configure MockMvc in a non-@WebMvcTest (such as @SpringBootTest ) by annotating it with @AutoConfigureMockMvc .
The following example uses MockMvc :
|
import org.junit.jupiter.api.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.web.servlet.*;
import org.springframework.boot.test.mock.mockito.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
@WebMvcTest(UserVehicleController.class)
class MyControllerTests {
@Autowired
private MockMvc mvc;
@MockBean
private UserVehicleService userVehicleService;
@Test
void testExample() throws Exception {
given(this.userVehicleService.getVehicleDetails("sboot"))
.willReturn(new VehicleDetails("Honda", "Civic"));
this.mvc.perform(get("/sboot/vehicle").accept(MediaType.TEXT_PLAIN))
.andExpect(status().isOk()).andExpect(content().string("Honda Civic"));
}
}
If you need to configure elements of the auto-configuration (for example, when servlet filters should be applied) you can use attributes in the @AutoConfigureMockMvc annotation.
|
If you use HtmlUnit or Selenium, auto-configuration also provides an HtmlUnit WebClient
bean and/or a Selenium WebDriver
bean.
The following example uses HtmlUnit:
import com.gargoylesoftware.htmlunit.*;
import org.junit.jupiter.api.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.web.servlet.*;
import org.springframework.boot.test.mock.mockito.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
@WebMvcTest(UserVehicleController.class)
class MyHtmlUnitTests {
@Autowired
private WebClient webClient;
@MockBean
private UserVehicleService userVehicleService;
@Test
void testExample() throws Exception {
given(this.userVehicleService.getVehicleDetails("sboot"))
.willReturn(new VehicleDetails("Honda", "Civic"));
HtmlPage page = this.webClient.getPage("/sboot/vehicle.html");
assertThat(page.getBody().getTextContent()).isEqualTo("Honda Civic");
}
}
By default, Spring Boot puts WebDriver beans in a special “scope” to ensure that the driver exits after each test and that a new instance is injected.
If you do not want this behavior, you can add @Scope("singleton") to your WebDriver @Bean definition.
|
The webDriver scope created by Spring Boot will replace any user defined scope of the same name.
If you define your own webDriver scope you may find it stops working when you use @WebMvcTest .
|
If you have Spring Security on the classpath, @WebMvcTest
will also scan WebSecurityConfigurer
beans.
Instead of disabling security completely for such tests, you can use Spring Security’s test support.
More details on how to use Spring Security’s MockMvc
support can be found in this howto.html how-to section.
Sometimes writing Spring MVC tests is not enough; Spring Boot can help you run full end-to-end tests with an actual server. |
25.3.13. Auto-configured Spring WebFlux Tests
To test that Spring WebFlux controllers are working as expected, you can use the @WebFluxTest
annotation.
@WebFluxTest
auto-configures the Spring WebFlux infrastructure and limits scanned beans to @Controller
, @ControllerAdvice
, @JsonComponent
, Converter
, GenericConverter
, WebFilter
, and WebFluxConfigurer
.
Regular @Component
beans are not scanned when the @WebFluxTest
annotation is used.
A list of the auto-configurations that are enabled by @WebFluxTest can be found in the appendix.
|
If you need to register extra components, such as Jackson Module , you can import additional configuration classes using @Import on your test.
|
Often, @WebFluxTest
is limited to a single controller and used in combination with the @MockBean
annotation to provide mock implementations for required collaborators.
@WebFluxTest
also auto-configures WebTestClient
, which offers a powerful way to quickly test WebFlux controllers without needing to start a full HTTP server.
You can also auto-configure WebTestClient in a non-@WebFluxTest (such as @SpringBootTest ) by annotating it with @AutoConfigureWebTestClient .
The following example shows a class that uses both @WebFluxTest and a WebTestClient :
|
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest;
import org.springframework.http.MediaType;
import org.springframework.test.web.reactive.server.WebTestClient;
@WebFluxTest(UserVehicleController.class)
class MyControllerTests {
@Autowired
private WebTestClient webClient;
@MockBean
private UserVehicleService userVehicleService;
@Test
void testExample() throws Exception {
given(this.userVehicleService.getVehicleDetails("sboot"))
.willReturn(new VehicleDetails("Honda", "Civic"));
this.webClient.get().uri("/sboot/vehicle").accept(MediaType.TEXT_PLAIN)
.exchange()
.expectStatus().isOk()
.expectBody(String.class).isEqualTo("Honda Civic");
}
}
This setup is only supported by WebFlux applications as using WebTestClient in a mocked web application only works with WebFlux at the moment.
|
@WebFluxTest cannot detect routes registered via the functional web framework.
For testing RouterFunction beans in the context, consider importing your RouterFunction yourself via @Import or using @SpringBootTest .
|
@WebFluxTest cannot detect custom security configuration registered via a @Bean of type SecurityWebFilterChain .
To include that in your test, you will need to import the configuration that registers the bean via @Import or use @SpringBootTest .
|
Sometimes writing Spring WebFlux tests is not enough; Spring Boot can help you run full end-to-end tests with an actual server. |
25.3.14. Auto-configured Data JPA Tests
You can use the @DataJpaTest
annotation to test JPA applications.
By default, it scans for @Entity
classes and configures Spring Data JPA repositories.
If an embedded database is available on the classpath, it configures one as well.
Regular @Component
beans are not loaded into the ApplicationContext
.
A list of the auto-configuration settings that are enabled by @DataJpaTest can be found in the appendix.
|
By default, data JPA tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@DataJpaTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
class ExampleNonTransactionalTests {
}
Data JPA tests may also inject a TestEntityManager
bean, which provides an alternative to the standard JPA EntityManager
that is specifically designed for tests.
If you want to use TestEntityManager
outside of @DataJpaTest
instances, you can also use the @AutoConfigureTestEntityManager
annotation.
A JdbcTemplate
is also available if you need that.
The following example shows the @DataJpaTest
annotation in use:
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.autoconfigure.orm.jpa.*;
import static org.assertj.core.api.Assertions.*;
@DataJpaTest
class ExampleRepositoryTests {
@Autowired
private TestEntityManager entityManager;
@Autowired
private UserRepository repository;
@Test
void testExample() throws Exception {
this.entityManager.persist(new User("sboot", "1234"));
User user = this.repository.findByUsername("sboot");
assertThat(user.getUsername()).isEqualTo("sboot");
assertThat(user.getVin()).isEqualTo("1234");
}
}
In-memory embedded databases generally work well for tests, since they are fast and do not require any installation.
If, however, you prefer to run tests against a real database you can use the @AutoConfigureTestDatabase
annotation, as shown in the following example:
@DataJpaTest
@AutoConfigureTestDatabase(replace=Replace.NONE)
class ExampleRepositoryTests {
// ...
}
25.3.15. Auto-configured JDBC Tests
@JdbcTest
is similar to @DataJpaTest
but is for tests that only require a DataSource
and do not use Spring Data JDBC.
By default, it configures an in-memory embedded database and a JdbcTemplate
.
Regular @Component
beans are not loaded into the ApplicationContext
.
A list of the auto-configurations that are enabled by @JdbcTest can be found in the appendix.
|
By default, JDBC tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class, as follows:
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.autoconfigure.jdbc.JdbcTest;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@JdbcTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
class ExampleNonTransactionalTests {
}
If you prefer your test to run against a real database, you can use the @AutoConfigureTestDatabase
annotation in the same way as for DataJpaTest
.
(See "Auto-configured Data JPA Tests".)
25.3.16. Auto-configured Data JDBC Tests
@DataJdbcTest
is similar to @JdbcTest
but is for tests that use Spring Data JDBC repositories.
By default, it configures an in-memory embedded database, a JdbcTemplate
, and Spring Data JDBC repositories.
Regular @Component
beans are not loaded into the ApplicationContext
.
A list of the auto-configurations that are enabled by @DataJdbcTest can be found in the appendix.
|
By default, Data JDBC tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole test class as shown in the JDBC example.
If you prefer your test to run against a real database, you can use the @AutoConfigureTestDatabase
annotation in the same way as for DataJpaTest
.
(See "Auto-configured Data JPA Tests".)
25.3.17. Auto-configured jOOQ Tests
You can use @JooqTest
in a similar fashion as @JdbcTest
but for jOOQ-related tests.
As jOOQ relies heavily on a Java-based schema that corresponds with the database schema, the existing DataSource
is used.
If you want to replace it with an in-memory database, you can use @AutoConfigureTestDatabase
to override those settings.
(For more about using jOOQ with Spring Boot, see "Using jOOQ", earlier in this chapter.)
Regular @Component
beans are not loaded into the ApplicationContext
.
A list of the auto-configurations that are enabled by @JooqTest can be found in the appendix.
|
@JooqTest
configures a DSLContext
.
Regular @Component
beans are not loaded into the ApplicationContext
.
The following example shows the @JooqTest
annotation in use:
import org.jooq.DSLContext;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.autoconfigure.jooq.JooqTest;
@JooqTest
class ExampleJooqTests {
@Autowired
private DSLContext dslContext;
}
JOOQ tests are transactional and roll back at the end of each test by default. If that is not what you want, you can disable transaction management for a test or for the whole test class as shown in the JDBC example.
25.3.18. Auto-configured Data MongoDB Tests
You can use @DataMongoTest
to test MongoDB applications.
By default, it configures an in-memory embedded MongoDB (if available), configures a MongoTemplate
, scans for @Document
classes, and configures Spring Data MongoDB repositories.
Regular @Component
beans are not loaded into the ApplicationContext
.
(For more about using MongoDB with Spring Boot, see "MongoDB", earlier in this chapter.)
A list of the auto-configuration settings that are enabled by @DataMongoTest can be found in the appendix.
|
The following class shows the @DataMongoTest
annotation in use:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
import org.springframework.data.mongodb.core.MongoTemplate;
@DataMongoTest
class ExampleDataMongoTests {
@Autowired
private MongoTemplate mongoTemplate;
//
}
In-memory embedded MongoDB generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real MongoDB server, you should exclude the embedded MongoDB auto-configuration, as shown in the following example:
import org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration;
import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
@DataMongoTest(excludeAutoConfiguration = EmbeddedMongoAutoConfiguration.class)
class ExampleDataMongoNonEmbeddedTests {
}
25.3.19. Auto-configured Data Neo4j Tests
You can use @DataNeo4jTest
to test Neo4j applications.
By default, it uses an in-memory embedded Neo4j (if the embedded driver is available), scans for @NodeEntity
classes, and configures Spring Data Neo4j repositories.
Regular @Component
beans are not loaded into the ApplicationContext
.
(For more about using Neo4J with Spring Boot, see "Neo4j", earlier in this chapter.)
A list of the auto-configuration settings that are enabled by @DataNeo4jTest can be found in the appendix.
|
The following example shows a typical setup for using Neo4J tests in Spring Boot:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest;
@DataNeo4jTest
class ExampleDataNeo4jTests {
@Autowired
private YourRepository repository;
//
}
By default, Data Neo4j tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class, as follows:
import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@DataNeo4jTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
class ExampleNonTransactionalTests {
}
25.3.20. Auto-configured Data Redis Tests
You can use @DataRedisTest
to test Redis applications.
By default, it scans for @RedisHash
classes and configures Spring Data Redis repositories.
Regular @Component
beans are not loaded into the ApplicationContext
.
(For more about using Redis with Spring Boot, see "Redis", earlier in this chapter.)
A list of the auto-configuration settings that are enabled by @DataRedisTest can be found in the appendix.
|
The following example shows the @DataRedisTest
annotation in use:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.redis.DataRedisTest;
@DataRedisTest
class ExampleDataRedisTests {
@Autowired
private YourRepository repository;
//
}
25.3.21. Auto-configured Data LDAP Tests
You can use @DataLdapTest
to test LDAP applications.
By default, it configures an in-memory embedded LDAP (if available), configures an LdapTemplate
, scans for @Entry
classes, and configures Spring Data LDAP repositories.
Regular @Component
beans are not loaded into the ApplicationContext
.
(For more about using LDAP with Spring Boot, see "LDAP", earlier in this chapter.)
A list of the auto-configuration settings that are enabled by @DataLdapTest can be found in the appendix.
|
The following example shows the @DataLdapTest
annotation in use:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest;
import org.springframework.ldap.core.LdapTemplate;
@DataLdapTest
class ExampleDataLdapTests {
@Autowired
private LdapTemplate ldapTemplate;
//
}
In-memory embedded LDAP generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real LDAP server, you should exclude the embedded LDAP auto-configuration, as shown in the following example:
import org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration;
import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest;
@DataLdapTest(excludeAutoConfiguration = EmbeddedLdapAutoConfiguration.class)
class ExampleDataLdapNonEmbeddedTests {
}
25.3.22. Auto-configured REST Clients
You can use the @RestClientTest
annotation to test REST clients.
By default, it auto-configures Jackson, GSON, and Jsonb support, configures a RestTemplateBuilder
, and adds support for MockRestServiceServer
.
Regular @Component
beans are not loaded into the ApplicationContext
.
A list of the auto-configuration settings that are enabled by @RestClientTest can be found in the appendix.
|
The specific beans that you want to test should be specified by using the value
or components
attribute of @RestClientTest
, as shown in the following example:
@RestClientTest(RemoteVehicleDetailsService.class)
class ExampleRestClientTest {
@Autowired
private RemoteVehicleDetailsService service;
@Autowired
private MockRestServiceServer server;
@Test
void getVehicleDetailsWhenResultIsSuccessShouldReturnDetails()
throws Exception {
this.server.expect(requestTo("/greet/details"))
.andRespond(withSuccess("hello", MediaType.TEXT_PLAIN));
String greeting = this.service.callRestService();
assertThat(greeting).isEqualTo("hello");
}
}
25.3.23. Auto-configured Spring REST Docs Tests
You can use the @AutoConfigureRestDocs
annotation to use Spring REST Docs in your tests with Mock MVC, REST Assured, or WebTestClient.
It removes the need for the JUnit extension in Spring REST Docs.
@AutoConfigureRestDocs
can be used to override the default output directory (target/generated-snippets
if you are using Maven or build/generated-snippets
if you are using Gradle).
It can also be used to configure the host, scheme, and port that appears in any documented URIs.
Auto-configured Spring REST Docs Tests with Mock MVC
@AutoConfigureRestDocs
customizes the MockMvc
bean to use Spring REST Docs.
You can inject it by using @Autowired
and use it in your tests as you normally would when using Mock MVC and Spring REST Docs, as shown in the following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.http.MediaType;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
@WebMvcTest(UserController.class)
@AutoConfigureRestDocs
class UserDocumentationTests {
@Autowired
private MockMvc mvc;
@Test
void listUsers() throws Exception {
this.mvc.perform(get("/users").accept(MediaType.TEXT_PLAIN))
.andExpect(status().isOk())
.andDo(document("list-users"));
}
}
If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs
, you can use a RestDocsMockMvcConfigurationCustomizer
bean, as shown in the following example:
@TestConfiguration
static class CustomizationConfiguration
implements RestDocsMockMvcConfigurationCustomizer {
@Override
public void customize(MockMvcRestDocumentationConfigurer configurer) {
configurer.snippets().withTemplateFormat(TemplateFormats.markdown());
}
}
If you want to make use of Spring REST Docs support for a parameterized output directory, you can create a RestDocumentationResultHandler
bean.
The auto-configuration calls alwaysDo
with this result handler, thereby causing each MockMvc
call to automatically generate the default snippets.
The following example shows a RestDocumentationResultHandler
being defined:
@TestConfiguration(proxyBeanMethods = false)
static class ResultHandlerConfiguration {
@Bean
public RestDocumentationResultHandler restDocumentation() {
return MockMvcRestDocumentation.document("{method-name}");
}
}
Auto-configured Spring REST Docs Tests with WebTestClient
@AutoConfigureRestDocs
can also be used with WebTestClient
.
You can inject it by using @Autowired
and use it in your tests as you normally would when using @WebFluxTest
and Spring REST Docs, as shown in the following example:
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.restdocs.AutoConfigureRestDocs;
import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest;
import org.springframework.test.web.reactive.server.WebTestClient;
import static org.springframework.restdocs.webtestclient.WebTestClientRestDocumentation.document;
@WebFluxTest
@AutoConfigureRestDocs
class UsersDocumentationTests {
@Autowired
private WebTestClient webTestClient;
@Test
void listUsers() {
this.webTestClient.get().uri("/").exchange().expectStatus().isOk().expectBody()
.consumeWith(document("list-users"));
}
}
If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs
, you can use a RestDocsWebTestClientConfigurationCustomizer
bean, as shown in the following example:
@TestConfiguration(proxyBeanMethods = false)
public static class CustomizationConfiguration implements RestDocsWebTestClientConfigurationCustomizer {
@Override
public void customize(WebTestClientRestDocumentationConfigurer configurer) {
configurer.snippets().withEncoding("UTF-8");
}
}
Auto-configured Spring REST Docs Tests with REST Assured
@AutoConfigureRestDocs
makes a RequestSpecification
bean, preconfigured to use Spring REST Docs, available to your tests.
You can inject it by using @Autowired
and use it in your tests as you normally would when using REST Assured and Spring REST Docs, as shown in the following example:
import io.restassured.specification.RequestSpecification;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.restdocs.AutoConfigureRestDocs;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.web.server.LocalServerPort;
import static io.restassured.RestAssured.given;
import static org.hamcrest.Matchers.is;
import static org.springframework.restdocs.restassured3.RestAssuredRestDocumentation.document;
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
@AutoConfigureRestDocs
class UserDocumentationTests {
@Test
void listUsers(@Autowired RequestSpecification documentationSpec, @LocalServerPort int port) {
given(documentationSpec).filter(document("list-users")).when().port(port).get("/").then().assertThat()
.statusCode(is(200));
}
}
If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs
, a RestDocsRestAssuredConfigurationCustomizer
bean can be used, as shown in the following example:
@TestConfiguration(proxyBeanMethods = false)
public static class CustomizationConfiguration implements RestDocsRestAssuredConfigurationCustomizer {
@Override
public void customize(RestAssuredRestDocumentationConfigurer configurer) {
configurer.snippets().withTemplateFormat(TemplateFormats.markdown());
}
}
25.3.24. Additional Auto-configuration and Slicing
Each slice provides one or more @AutoConfigure…
annotations that namely defines the auto-configurations that should be included as part of a slice.
Additional auto-configurations can be added by creating a custom @AutoConfigure…
annotation or simply by adding @ImportAutoConfiguration
to the test as shown in the following example:
@JdbcTest
@ImportAutoConfiguration(IntegrationAutoConfiguration.class)
class ExampleJdbcTests {
}
Make sure to not use the regular @Import annotation to import auto-configurations as they are handled in a specific way by Spring Boot.
|
25.3.25. User Configuration and Slicing
If you structure your code in a sensible way, your @SpringBootApplication
class is used by default as the configuration of your tests.
It then becomes important not to litter the application’s main class with configuration settings that are specific to a particular area of its functionality.
Assume that you are using Spring Batch and you rely on the auto-configuration for it.
You could define your @SpringBootApplication
as follows:
@SpringBootApplication
@EnableBatchProcessing
public class SampleApplication { ... }
Because this class is the source configuration for the test, any slice test actually tries to start Spring Batch, which is definitely not what you want to do.
A recommended approach is to move that area-specific configuration to a separate @Configuration
class at the same level as your application, as shown in the following example:
@Configuration(proxyBeanMethods = false)
@EnableBatchProcessing
public class BatchConfiguration { ... }
Depending on the complexity of your application, you may either have a single @Configuration class for your customizations or one class per domain area.
The latter approach lets you enable it in one of your tests, if necessary, with the @Import annotation.
|
Test slices exclude @Configuration
classes from scanning.
For example, for a @WebMvcTest
, the following configuration will not include the given WebMvcConfigurer
bean in the application context loaded by the test slice:
@Configuration
public class WebConfiguration {
@Bean
public WebMvcConfigurer testConfigurer() {
return new WebMvcConfigurer() {
...
};
}
}
The configuration below will, however, cause the custom WebMvcConfigurer
to be loaded by the test slice.
@Component
public class TestWebMvcConfigurer implements WebMvcConfigurer {
...
}
Another source of confusion is classpath scanning. Assume that, while you structured your code in a sensible way, you need to scan an additional package. Your application may resemble the following code:
@SpringBootApplication
@ComponentScan({ "com.example.app", "org.acme.another" })
public class SampleApplication { ... }
Doing so effectively overrides the default component scan directive with the side effect of scanning those two packages regardless of the slice that you chose.
For instance, a @DataJpaTest
seems to suddenly scan components and user configurations of your application.
Again, moving the custom directive to a separate class is a good way to fix this issue.
If this is not an option for you, you can create a @SpringBootConfiguration somewhere in the hierarchy of your test so that it is used instead.
Alternatively, you can specify a source for your test, which disables the behavior of finding a default one.
|
25.3.26. Using Spock to Test Spring Boot Applications
If you wish to use Spock to test a Spring Boot application, you should add a dependency on Spock’s spock-spring
module to your application’s build.
spock-spring
integrates Spring’s test framework into Spock.
It is recommended that you use Spock 1.2 or later to benefit from a number of improvements to Spock’s Spring Framework and Spring Boot integration.
See the documentation for Spock’s Spring module for further details.
25.4. Test Utilities
A few test utility classes that are generally useful when testing your application are packaged as part of spring-boot
.
25.4.1. ConfigFileApplicationContextInitializer
ConfigFileApplicationContextInitializer
is an ApplicationContextInitializer
that you can apply to your tests to load Spring Boot application.properties
files.
You can use it when you do not need the full set of features provided by @SpringBootTest
, as shown in the following example:
@ContextConfiguration(classes = Config.class,
initializers = ConfigFileApplicationContextInitializer.class)
Using ConfigFileApplicationContextInitializer alone does not provide support for @Value("${…}") injection.
Its only job is to ensure that application.properties files are loaded into Spring’s Environment .
For @Value support, you need to either additionally configure a PropertySourcesPlaceholderConfigurer or use @SpringBootTest , which auto-configures one for you.
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25.4.2. TestPropertyValues
TestPropertyValues
lets you quickly add properties to a ConfigurableEnvironment
or ConfigurableApplicationContext
.
You can call it with key=value
strings, as follows:
TestPropertyValues.of("org=Spring", "name=Boot").applyTo(env);
25.4.3. OutputCapture
OutputCapture
is a JUnit Extension
that you can use to capture System.out
and System.err
output.
To use add @ExtendWith(OutputCaptureExtension.class)
and inject CapturedOutput
as an argument to your test class constructor or test method as follows:
@ExtendWith(OutputCaptureExtension.class)
class OutputCaptureTests {
@Test
void testName(CapturedOutput output) {
System.out.println("Hello World!");
assertThat(output).contains("World");
}
}
25.4.4. TestRestTemplate
TestRestTemplate
is a convenience alternative to Spring’s RestTemplate
that is useful in integration tests.
You can get a vanilla template or one that sends Basic HTTP authentication (with a username and password).
In either case, the template behaves in a test-friendly way by not throwing exceptions on server-side errors.
Spring Framework 5.0 provides a new WebTestClient that works for WebFlux integration tests and both WebFlux and MVC end-to-end testing.
It provides a fluent API for assertions, unlike TestRestTemplate .
|
It is recommended, but not mandatory, to use the Apache HTTP Client (version 4.3.2 or better).
If you have that on your classpath, the TestRestTemplate
responds by configuring the client appropriately.
If you do use Apache’s HTTP client, some additional test-friendly features are enabled:
-
Redirects are not followed (so you can assert the response location).
-
Cookies are ignored (so the template is stateless).
TestRestTemplate
can be instantiated directly in your integration tests, as shown in the following example:
public class MyTest {
private TestRestTemplate template = new TestRestTemplate();
@Test
public void testRequest() throws Exception {
HttpHeaders headers = this.template.getForEntity(
"https://myhost.example.com/example", String.class).getHeaders();
assertThat(headers.getLocation()).hasHost("other.example.com");
}
}
Alternatively, if you use the @SpringBootTest
annotation with WebEnvironment.RANDOM_PORT
or WebEnvironment.DEFINED_PORT
, you can inject a fully configured TestRestTemplate
and start using it.
If necessary, additional customizations can be applied through the RestTemplateBuilder
bean.
Any URLs that do not specify a host and port automatically connect to the embedded server, as shown in the following example:
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class SampleWebClientTests {
@Autowired
private TestRestTemplate template;
@Test
void testRequest() {
HttpHeaders headers = this.template.getForEntity("/example", String.class).getHeaders();
assertThat(headers.getLocation()).hasHost("other.example.com");
}
@TestConfiguration(proxyBeanMethods = false)
static class Config {
@Bean
RestTemplateBuilder restTemplateBuilder() {
return new RestTemplateBuilder().setConnectTimeout(Duration.ofSeconds(1))
.setReadTimeout(Duration.ofSeconds(1));
}
}
}
26. WebSockets
Spring Boot provides WebSockets auto-configuration for embedded Tomcat, Jetty, and Undertow. If you deploy a war file to a standalone container, Spring Boot assumes that the container is responsible for the configuration of its WebSocket support.
Spring Framework provides rich WebSocket support for MVC web applications that can be easily accessed through the spring-boot-starter-websocket
module.
WebSocket support is also available for reactive web applications and requires to include the WebSocket API alongside spring-boot-starter-webflux
:
<dependency>
<groupId>javax.websocket</groupId>
<artifactId>javax.websocket-api</artifactId>
</dependency>
27. Web Services
Spring Boot provides Web Services auto-configuration so that all you must do is define your Endpoints
.
The Spring Web Services features can be easily accessed with the spring-boot-starter-webservices
module.
SimpleWsdl11Definition
and SimpleXsdSchema
beans can be automatically created for your WSDLs and XSDs respectively.
To do so, configure their location, as shown in the following example:
spring.webservices.wsdl-locations=classpath:/wsdl
27.1. Calling Web Services with WebServiceTemplate
If you need to call remote Web services from your application, you can use the WebServiceTemplate
class.
Since WebServiceTemplate
instances often need to be customized before being used, Spring Boot does not provide any single auto-configured WebServiceTemplate
bean.
It does, however, auto-configure a WebServiceTemplateBuilder
, which can be used to create WebServiceTemplate
instances when needed.
The following code shows a typical example:
@Service
public class MyService {
private final WebServiceTemplate webServiceTemplate;
public MyService(WebServiceTemplateBuilder webServiceTemplateBuilder) {
this.webServiceTemplate = webServiceTemplateBuilder.build();
}
public DetailsResp someWsCall(DetailsReq detailsReq) {
return (DetailsResp) this.webServiceTemplate.marshalSendAndReceive(detailsReq, new SoapActionCallback(ACTION));
}
}
By default, WebServiceTemplateBuilder
detects a suitable HTTP-based WebServiceMessageSender
using the available HTTP client libraries on the classpath.
You can also customize read and connection timeouts as follows:
@Bean
public WebServiceTemplate webServiceTemplate(WebServiceTemplateBuilder builder) {
return builder.messageSenders(new HttpWebServiceMessageSenderBuilder()
.setConnectTimeout(5000).setReadTimeout(2000).build()).build();
}
28. Creating Your Own Auto-configuration
If you work in a company that develops shared libraries, or if you work on an open-source or commercial library, you might want to develop your own auto-configuration. Auto-configuration classes can be bundled in external jars and still be picked-up by Spring Boot.
Auto-configuration can be associated to a “starter” that provides the auto-configuration code as well as the typical libraries that you would use with it. We first cover what you need to know to build your own auto-configuration and then we move on to the typical steps required to create a custom starter.
A demo project is available to showcase how you can create a starter step-by-step. |
28.1. Understanding Auto-configured Beans
Under the hood, auto-configuration is implemented with standard @Configuration
classes.
Additional @Conditional
annotations are used to constrain when the auto-configuration should apply.
Usually, auto-configuration classes use @ConditionalOnClass
and @ConditionalOnMissingBean
annotations.
This ensures that auto-configuration applies only when relevant classes are found and when you have not declared your own @Configuration
.
You can browse the source code of spring-boot-autoconfigure
to see the @Configuration
classes that Spring provides (see the META-INF/spring.factories
file).
28.2. Locating Auto-configuration Candidates
Spring Boot checks for the presence of a META-INF/spring.factories
file within your published jar.
The file should list your configuration classes under the EnableAutoConfiguration
key, as shown in the following example:
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.mycorp.libx.autoconfigure.LibXAutoConfiguration,\ com.mycorp.libx.autoconfigure.LibXWebAutoConfiguration
Auto-configurations must be loaded that way only.
Make sure that they are defined in a specific package space and that they are never the target of component scanning.
Furthermore, auto-configuration classes should not enable component scanning to find additional components.
Specific @Import s should be used instead.
|
You can use the @AutoConfigureAfter
or @AutoConfigureBefore
annotations if your configuration needs to be applied in a specific order.
For example, if you provide web-specific configuration, your class may need to be applied after WebMvcAutoConfiguration
.
If you want to order certain auto-configurations that should not have any direct knowledge of each other, you can also use @AutoConfigureOrder
.
That annotation has the same semantic as the regular @Order
annotation but provides a dedicated order for auto-configuration classes.
28.3. Condition Annotations
You almost always want to include one or more @Conditional
annotations on your auto-configuration class.
The @ConditionalOnMissingBean
annotation is one common example that is used to allow developers to override auto-configuration if they are not happy with your defaults.
Spring Boot includes a number of @Conditional
annotations that you can reuse in your own code by annotating @Configuration
classes or individual @Bean
methods.
These annotations include:
28.3.1. Class Conditions
The @ConditionalOnClass
and @ConditionalOnMissingClass
annotations let @Configuration
classes be included based on the presence or absence of specific classes.
Due to the fact that annotation metadata is parsed by using ASM, you can use the value
attribute to refer to the real class, even though that class might not actually appear on the running application classpath.
You can also use the name
attribute if you prefer to specify the class name by using a String
value.
This mechanism does not apply the same way to @Bean
methods where typically the return type is the target of the condition: before the condition on the method applies, the JVM will have loaded the class and potentially processed method references which will fail if the class is not present.
To handle this scenario, a separate @Configuration
class can be used to isolate the condition, as shown in the following example:
@Configuration(proxyBeanMethods = false)
// Some conditions
public class MyAutoConfiguration {
// Auto-configured beans
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(EmbeddedAcmeService.class)
static class EmbeddedConfiguration {
@Bean
@ConditionalOnMissingBean
public EmbeddedAcmeService embeddedAcmeService() { ... }
}
}
If you use @ConditionalOnClass or @ConditionalOnMissingClass as a part of a meta-annotation to compose your own composed annotations, you must use name as referring to the class in such a case is not handled.
|
28.3.2. Bean Conditions
The @ConditionalOnBean
and @ConditionalOnMissingBean
annotations let a bean be included based on the presence or absence of specific beans.
You can use the value
attribute to specify beans by type or name
to specify beans by name.
The search
attribute lets you limit the ApplicationContext
hierarchy that should be considered when searching for beans.
When placed on a @Bean
method, the target type defaults to the return type of the method, as shown in the following example:
@Configuration(proxyBeanMethods = false)
public class MyAutoConfiguration {
@Bean
@ConditionalOnMissingBean
public MyService myService() { ... }
}
In the preceding example, the myService
bean is going to be created if no bean of type MyService
is already contained in the ApplicationContext
.
You need to be very careful about the order in which bean definitions are added, as these conditions are evaluated based on what has been processed so far.
For this reason, we recommend using only @ConditionalOnBean and @ConditionalOnMissingBean annotations on auto-configuration classes (since these are guaranteed to load after any user-defined bean definitions have been added).
|
@ConditionalOnBean and @ConditionalOnMissingBean do not prevent @Configuration classes from being created.
The only difference between using these conditions at the class level and marking each contained @Bean method with the annotation is that the former prevents registration of the @Configuration class as a bean if the condition does not match.
|
28.3.3. Property Conditions
The @ConditionalOnProperty
annotation lets configuration be included based on a Spring Environment property.
Use the prefix
and name
attributes to specify the property that should be checked.
By default, any property that exists and is not equal to false
is matched.
You can also create more advanced checks by using the havingValue
and matchIfMissing
attributes.
28.3.4. Resource Conditions
The @ConditionalOnResource
annotation lets configuration be included only when a specific resource is present.
Resources can be specified by using the usual Spring conventions, as shown in the following example: file:/home/user/test.dat
.
28.3.5. Web Application Conditions
The @ConditionalOnWebApplication
and @ConditionalOnNotWebApplication
annotations let configuration be included depending on whether the application is a “web application”.
A servlet-based web application is any application that uses a Spring WebApplicationContext
, defines a session
scope, or has a ConfigurableWebEnvironment
.
A reactive web application is any application that uses a ReactiveWebApplicationContext
, or has a ConfigurableReactiveWebEnvironment
.
28.3.6. SpEL Expression Conditions
The @ConditionalOnExpression
annotation lets configuration be included based on the result of a SpEL expression.
28.4. Testing your Auto-configuration
An auto-configuration can be affected by many factors: user configuration (@Bean
definition and Environment
customization), condition evaluation (presence of a particular library), and others.
Concretely, each test should create a well defined ApplicationContext
that represents a combination of those customizations.
ApplicationContextRunner
provides a great way to achieve that.
ApplicationContextRunner
is usually defined as a field of the test class to gather the base, common configuration.
The following example makes sure that UserServiceAutoConfiguration
is always invoked:
private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
.withConfiguration(AutoConfigurations.of(UserServiceAutoConfiguration.class));
If multiple auto-configurations have to be defined, there is no need to order their declarations as they are invoked in the exact same order as when running the application. |
Each test can use the runner to represent a particular use case.
For instance, the sample below invokes a user configuration (UserConfiguration
) and checks that the auto-configuration backs off properly.
Invoking run
provides a callback context that can be used with Assert4J
.
@Test
void defaultServiceBacksOff() {
this.contextRunner.withUserConfiguration(UserConfiguration.class).run((context) -> {
assertThat(context).hasSingleBean(UserService.class);
assertThat(context).getBean("myUserService").isSameAs(context.getBean(UserService.class));
});
}
@Configuration(proxyBeanMethods = false)
static class UserConfiguration {
@Bean
UserService myUserService() {
return new UserService("mine");
}
}
It is also possible to easily customize the Environment
, as shown in the following example:
@Test
void serviceNameCanBeConfigured() {
this.contextRunner.withPropertyValues("user.name=test123").run((context) -> {
assertThat(context).hasSingleBean(UserService.class);
assertThat(context.getBean(UserService.class).getName()).isEqualTo("test123");
});
}
The runner can also be used to display the ConditionEvaluationReport
.
The report can be printed at INFO
or DEBUG
level.
The following example shows how to use the ConditionEvaluationReportLoggingListener
to print the report in auto-configuration tests.
@Test
public void autoConfigTest {
ConditionEvaluationReportLoggingListener initializer = new ConditionEvaluationReportLoggingListener(
LogLevel.INFO);
ApplicationContextRunner contextRunner = new ApplicationContextRunner()
.withInitializer(initializer).run((context) -> {
// Do something...
});
}
28.4.1. Simulating a Web Context
If you need to test an auto-configuration that only operates in a Servlet or Reactive web application context, use the WebApplicationContextRunner
or ReactiveWebApplicationContextRunner
respectively.
28.4.2. Overriding the Classpath
It is also possible to test what happens when a particular class and/or package is not present at runtime.
Spring Boot ships with a FilteredClassLoader
that can easily be used by the runner.
In the following example, we assert that if UserService
is not present, the auto-configuration is properly disabled:
@Test
void serviceIsIgnoredIfLibraryIsNotPresent() {
this.contextRunner.withClassLoader(new FilteredClassLoader(UserService.class))
.run((context) -> assertThat(context).doesNotHaveBean("userService"));
}
28.5. Creating Your Own Starter
A full Spring Boot starter for a library may contain the following components:
-
The
autoconfigure
module that contains the auto-configuration code. -
The
starter
module that provides a dependency to theautoconfigure
module as well as the library and any additional dependencies that are typically useful. In a nutshell, adding the starter should provide everything needed to start using that library.
You may combine the auto-configuration code and the dependency management in a single module if you do not need to separate those two concerns. |
28.5.1. Naming
You should make sure to provide a proper namespace for your starter.
Do not start your module names with spring-boot
, even if you use a different Maven groupId
.
We may offer official support for the thing you auto-configure in the future.
As a rule of thumb, you should name a combined module after the starter.
For example, assume that you are creating a starter for "acme" and that you name the auto-configure module acme-spring-boot-autoconfigure
and the starter acme-spring-boot-starter
.
If you only have one module that combines the two, name it acme-spring-boot-starter
.
28.5.2. Configuration keys
If your starter provides configuration keys, use a unique namespace for them.
In particular, do not include your keys in the namespaces that Spring Boot uses (such as server
, management
, spring
, and so on).
If you use the same namespace, we may modify these namespaces in the future in ways that break your modules.
As a rule of thumb, prefix all your keys with a namespace that you own (e.g. acme
).
Make sure that configuration keys are documented by adding field javadoc for each property, as shown in the following example:
@ConfigurationProperties("acme")
public class AcmeProperties {
/**
* Whether to check the location of acme resources.
*/
private boolean checkLocation = true;
/**
* Timeout for establishing a connection to the acme server.
*/
private Duration loginTimeout = Duration.ofSeconds(3);
// getters & setters
}
You should only use simple text with @ConfigurationProperties field Javadoc, since they are not processed before being added to the JSON.
|
Here are some rules we follow internally to make sure descriptions are consistent:
-
Do not start the description by "The" or "A".
-
For
boolean
types, start the description with "Whether" or "Enable". -
For collection-based types, start the description with "Comma-separated list"
-
Use
java.time.Duration
rather thanlong
and describe the default unit if it differs from milliseconds, e.g. "If a duration suffix is not specified, seconds will be used". -
Do not provide the default value in the description unless it has to be determined at runtime.
Make sure to trigger meta-data generation so that IDE assistance is available for your keys as well.
You may want to review the generated metadata (META-INF/spring-configuration-metadata.json
) to make sure your keys are properly documented.
Using your own starter in a compatible IDE is also a good idea to validate that quality of the metadata.
28.5.3. autoconfigure
Module
The autoconfigure
module contains everything that is necessary to get started with the library.
It may also contain configuration key definitions (such as @ConfigurationProperties
) and any callback interface that can be used to further customize how the components are initialized.
You should mark the dependencies to the library as optional so that you can include the autoconfigure module in your projects more easily.
If you do it that way, the library is not provided and, by default, Spring Boot backs off.
|
Spring Boot uses an annotation processor to collect the conditions on auto-configurations in a metadata file (META-INF/spring-autoconfigure-metadata.properties
).
If that file is present, it is used to eagerly filter auto-configurations that do not match, which will improve startup time.
It is recommended to add the following dependency in a module that contains auto-configurations:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure-processor</artifactId>
<optional>true</optional>
</dependency>
With Gradle 4.5 and earlier, the dependency should be declared in the compileOnly
configuration, as shown in the following example:
dependencies {
compileOnly "org.springframework.boot:spring-boot-autoconfigure-processor"
}
With Gradle 4.6 and later, the dependency should be declared in the annotationProcessor
configuration, as shown in the following example:
dependencies {
annotationProcessor "org.springframework.boot:spring-boot-autoconfigure-processor"
}
28.5.4. Starter Module
The starter is really an empty jar. Its only purpose is to provide the necessary dependencies to work with the library. You can think of it as an opinionated view of what is required to get started.
Do not make assumptions about the project in which your starter is added. If the library you are auto-configuring typically requires other starters, mention them as well. Providing a proper set of default dependencies may be hard if the number of optional dependencies is high, as you should avoid including dependencies that are unnecessary for a typical usage of the library. In other words, you should not include optional dependencies.
Either way, your starter must reference the core Spring Boot starter (spring-boot-starter ) directly or indirectly (i.e. no need to add it if your starter relies on another starter).
If a project is created with only your custom starter, Spring Boot’s core features will be honoured by the presence of the core starter.
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29. Kotlin support
Kotlin is a statically-typed language targeting the JVM (and other platforms) which allows writing concise and elegant code while providing interoperability with existing libraries written in Java.
Spring Boot provides Kotlin support by leveraging the support in other Spring projects such as Spring Framework, Spring Data, and Reactor. See the Spring Framework Kotlin support documentation for more information.
The easiest way to start with Spring Boot and Kotlin is to follow this comprehensive tutorial.
You can create new Kotlin projects via start.spring.io.
Feel free to join the #spring channel of Kotlin Slack or ask a question with the spring
and kotlin
tags on Stack Overflow if you need support.
29.1. Requirements
Spring Boot supports Kotlin 1.3.x.
To use Kotlin, org.jetbrains.kotlin:kotlin-stdlib
and org.jetbrains.kotlin:kotlin-reflect
must be present on the classpath.
The kotlin-stdlib
variants kotlin-stdlib-jdk7
and kotlin-stdlib-jdk8
can also be used.
Since Kotlin classes are final by default, you are likely to want to configure kotlin-spring plugin in order to automatically open Spring-annotated classes so that they can be proxied.
Jackson’s Kotlin module is required for serializing / deserializing JSON data in Kotlin. It is automatically registered when found on the classpath. A warning message is logged if Jackson and Kotlin are present but the Jackson Kotlin module is not.
These dependencies and plugins are provided by default if one bootstraps a Kotlin project on start.spring.io. |
29.2. Null-safety
One of Kotlin’s key features is null-safety.
It deals with null
values at compile time rather than deferring the problem to runtime and encountering a NullPointerException
.
This helps to eliminate a common source of bugs without paying the cost of wrappers like Optional
.
Kotlin also allows using functional constructs with nullable values as described in this comprehensive guide to null-safety in Kotlin.
Although Java does not allow one to express null-safety in its type system, Spring Framework, Spring Data, and Reactor now provide null-safety of their API via tooling-friendly annotations. By default, types from Java APIs used in Kotlin are recognized as platform types for which null-checks are relaxed. Kotlin’s support for JSR 305 annotations combined with nullability annotations provide null-safety for the related Spring API in Kotlin.
The JSR 305 checks can be configured by adding the -Xjsr305
compiler flag with the following options: -Xjsr305={strict|warn|ignore}
.
The default behavior is the same as -Xjsr305=warn
.
The strict
value is required to have null-safety taken in account in Kotlin types inferred from Spring API but should be used with the knowledge that Spring API nullability declaration could evolve even between minor releases and more checks may be added in the future).
Generic type arguments, varargs and array elements nullability are not yet supported. See SPR-15942 for up-to-date information. Also be aware that Spring Boot’s own API is not yet annotated. |
29.3. Kotlin API
29.3.1. runApplication
Spring Boot provides an idiomatic way to run an application with runApplication<MyApplication>(*args)
as shown in the following example:
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
@SpringBootApplication
class MyApplication
fun main(args: Array<String>) {
runApplication<MyApplication>(*args)
}
This is a drop-in replacement for SpringApplication.run(MyApplication::class.java, *args)
.
It also allows customization of the application as shown in the following example:
runApplication<MyApplication>(*args) {
setBannerMode(OFF)
}
29.3.2. Extensions
Kotlin extensions provide the ability to extend existing classes with additional functionality. The Spring Boot Kotlin API makes use of these extensions to add new Kotlin specific conveniences to existing APIs.
TestRestTemplate
extensions, similar to those provided by Spring Framework for RestOperations
in Spring Framework, are provided.
Among other things, the extensions make it possible to take advantage of Kotlin reified type parameters.
29.4. Dependency management
In order to avoid mixing different versions of Kotlin dependencies on the classpath, Spring Boot imports the Kotlin BOM.
With Maven, the Kotlin version can be customized via the kotlin.version
property and plugin management is provided for kotlin-maven-plugin
.
With Gradle, the Spring Boot plugin automatically aligns the kotlin.version
with the version of the Kotlin plugin.
Spring Boot also manages the version of Coroutines dependencies by importing the Kotlin Coroutines BOM.
The version can be customized via the kotlin-coroutines.version
property.
org.jetbrains.kotlinx:kotlinx-coroutines-reactor dependency is provided by default if one bootstraps a Kotlin project with at least one reactive dependency on start.spring.io.
|
29.5. @ConfigurationProperties
@ConfigurationProperties
when used in combination with @ConstructorBinding
supports classes with immutable val
properties as shown in the following example:
@ConstructorBinding
@ConfigurationProperties("example.kotlin")
data class KotlinExampleProperties(
val name: String,
val description: String,
val myService: MyService) {
data class MyService(
val apiToken: String,
val uri: URI
)
}
To generate your own metadata using the annotation processor, kapt should be configured with the spring-boot-configuration-processor dependency.
Note that some features (such as detecting the default value or deprecated items) are not working due to limitations in the model kapt provides.
|
29.6. Testing
While it is possible to use JUnit 4 to test Kotlin code, JUnit 5 is provided by default and is recommended.
JUnit 5 enables a test class to be instantiated once and reused for all of the class’s tests.
This makes it possible to use @BeforeClass
and @AfterClass
annotations on non-static methods, which is a good fit for Kotlin.
JUnit 5 is the default and the vintage engine is provided for backward compatibility with JUnit 4.
If you don’t use it, exclude org.junit.vintange:junit-vintage-engine
.
You also need to switch test instance lifecycle to "per-class".
To mock Kotlin classes, MockK is recommended.
If you need the Mockk
equivalent of the Mockito specific @MockBean
and @SpyBean
annotations, you can use SpringMockK which provides similar @MockkBean
and @SpykBean
annotations.
29.7. Resources
29.7.1. Further reading
-
Kotlin Slack (with a dedicated #spring channel)
-
Tutorial: building web applications with Spring Boot and Kotlin
-
A Geospatial Messenger with Kotlin, Spring Boot and PostgreSQL
29.7.2. Examples
-
spring-boot-kotlin-demo: regular Spring Boot + Spring Data JPA project
-
mixit: Spring Boot 2 + WebFlux + Reactive Spring Data MongoDB
-
spring-kotlin-fullstack: WebFlux Kotlin fullstack example with Kotlin2js for frontend instead of JavaScript or TypeScript
-
spring-petclinic-kotlin: Kotlin version of the Spring PetClinic Sample Application
-
spring-kotlin-deepdive: a step by step migration for Boot 1.0 + Java to Boot 2.0 + Kotlin
-
spring-boot-coroutines-demo: Coroutines sample project
29.8. Building Docker Images
Spring Boot applications can be containerized by packaging them into Docker images. A typical Spring Boot fat jar can be converted into a Docker image by adding just a few lines to a Dockerfile that can be used to build the image. However, there are various downsides to copying and running the fat jar as is in the docker image. There’s always a certain amount of overhead when running a fat jar without unpacking it, and in a containerized environment this can be noticeable. The other issue is that putting your application’s code and all its dependencies in one layer in the Docker image is sub-optimal. Since you probably recompile your code more often than you upgrade the version of Spring Boot you use, it’s often better to separate things a bit more. If you put jar files in the layer before your application classes, Docker often only needs to change the very bottom layer and can pick others up from its cache.
29.8.1. Layered Jars
To make it easier to create optimized Docker images that can be built with a dockerfile, Spring Boot supports "layered jars".
A regular fat jar that can be run with java -jar
has the following structure:
META-INF/
MANIFEST.MF
org/
springframework/
boot/
loader/
...
BOOT-INF/
classes/
...
lib/
...
The jar is organized into three main parts:
-
Classes used to bootstrap jar loading
-
Your application classes in
BOOT-INF/classes
-
Dependencies in
BOOT-INF/lib
Instead of the above jar, you can create a layered jar that looks something like this:
META-INF/
MANIFEST.MF
org/
springframework/
boot/
loader/
...
BOOT-INF/
layers/
<name>/
classes/
...
lib/
...
<name>/
classes/
...
lib/
...
layers.idx
You still see the bootstrap loader classes (you can still run java -jar
) but now the lib
and classes
folders have been split up and categorized into layers.
There’s also a layers.idx
file that provides the order in which layers should be added.
Out-of-the-box, the following layers are supported:
-
dependencies
(for regular released dependencies) -
snapshot-dependencies
(for snapshot dependencies) -
resources
(for static resources) -
application
(for application classes and resources)
This layering is designed to separate code based on how likely it is to change between application builds. Library code is less likely to change between builds, so it is placed in its own layers to allow tooling to re-use the layers from cache. Application code is more likely to change between builds so it is isolated in a separate layer.
For Maven, layered jars can be created using a new layout
type called LAYERED_JAR
.
See the layout section for more details.
For Gradle, refer to the packaging layered jars section of the Gradle plugin documentation.
29.8.2. Writing the Dockerfile
When you create a layered jar, the spring-boot-layertools
jar will be added as a dependency to your jar.
With this jar on the classpath, you can launch your application in a special mode which allows the bootstrap code to run something entirely different from your application, for example, something that extracts the layers.
Here’s how you can launch your jar with a layertools
jar mode:
$ java -Djarmode=layertools -jar my-app.jar
This will provide the following output:
Usage:
java -Djarmode=layertools -jar my-app.jar
Available commands:
list List layers from the jar that can be extracted
extract Extracts layers from the jar for image creation
help Help about any command
The extract
command can be used to easily split the application into layers to be added to the dockerfile.
Here’s an example of a Dockerfile using jarmode
.
FROM adoptopenjdk:11-jre-hotspot as builder
WORKDIR application
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} application.jar
RUN java -Djarmode=layertools -jar application.jar extract
FROM adoptopenjdk:11-jre-hotspot
WORKDIR application
COPY --from=builder application/dependencies/ ./
COPY --from=builder application/snapshot-dependencies/ ./
COPY --from=builder application/resources/ ./
COPY --from=builder application/application/ ./
ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]
This is a multi-stage dockerfile.
The builder stage extracts the folders that are needed later.
Each of the COPY
commands relates to the layers extracted by the jarmode.
Of course, a Dockerfile can be written without using the jarmode.
You can use some combination of unzip
and mv
to move things to the right layer but jarmode simplifies that.
29.8.3. Buildpacks
Dockerfiles are just one way to build docker images.
Another way to build docker images is directly from your Maven or Gradle plugin, using buildpacks.
If you’ve ever used an application platform such as Cloud Foundry or Heroku then you’ve probably used a buildpack.
Buildpacks are the part of the platform that takes your application and converts it into something that the platform can actually run.
For example, Cloud Foundry’s Java buildpack will notice that you’re pushing a .jar
file and automatically add a relevant JRE.
With Cloud Native Buildpacks, you can create Docker compatible images that you can run anywhere. Spring Boot includes buildpack support directly for both Maven and Gradle. This means you can just type a single command and quickly get a sensible image into your locally running Docker daemon.
30. What to Read Next
If you want to learn more about any of the classes discussed in this section, you can check out the Spring Boot API documentation or you can browse the source code directly. If you have specific questions, take a look at the how-to section.
If you are comfortable with Spring Boot’s core features, you can continue on and read about production-ready features.