Each Spring Boot web application includes an embedded web server. This feature leads to a number of how-to questions, including how to change the embedded server and how to configure the embedded server. This section answers those questions.
Many Spring Boot starters include default embedded containers. spring-boot-starter-web
includes Tomcat by including spring-boot-starter-tomcat
, but you can use
spring-boot-starter-jetty
and spring-boot-starter-undertow
instead.
spring-boot-starter-webflux
includes Reactor Netty by including
spring-boot-starter-reactor-netty
, but you can use spring-boot-starter-tomcat
,
spring-boot-starter-jetty
, and spring-boot-starter-undertow
instead.
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Many starters support only Spring MVC, so they transitively bring
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If you need to use a different HTTP server, you need to exclude the default dependencies and include the one you need. Spring Boot provides separate starters for HTTP servers to help make this process as easy as possible.
The following Maven example shows how to exclude Tomcat and include Jetty for Spring MVC:
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <!-- Exclude the Tomcat dependency --> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </exclusion> </exclusions> </dependency> <!-- Use Jetty instead --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jetty</artifactId> </dependency>
The following Gradle example shows how to exclude Netty and include Undertow for Spring WebFlux:
configurations { // exclude Reactor Netty compile.exclude module: 'spring-boot-starter-reactor-netty' } dependencies { compile 'org.springframework.boot:spring-boot-starter-webflux' // Use Undertow instead compile 'org.springframework.boot:spring-boot-starter-undertow' // ... }
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Generally, you can follow the advice from
“Section 73.8, “Discover Built-in Options for External Properties”” about
@ConfigurationProperties
(ServerProperties
is the main one here). However, you should
also look at ServletWebServerFactoryCustomizer
. The Jetty APIs are quite rich, so, once
you have access to the JettyServletWebServerFactory
, you can modify it in a number of
ways. Alternatively, if you need more control and customization, you can add your own
JettyServletWebServerFactory
.
There are two ways to add Servlet
, Filter
, ServletContextListener
, and the other
listeners supported by the Servlet spec to your application. You can either provide
Spring beans for them or enable scanning for Servlet components.
To add a Servlet
, Filter
, or Servlet *Listener
by using a Spring bean, you must
provide a @Bean
definition for it. Doing so can be very useful when you want to inject
configuration or dependencies. However, you must be very careful that they do not cause
eager initialization of too many other beans, because they have to be installed in the
container very early in the application lifecycle (for example, it is not a good idea to
have them depend on your DataSource
or JPA configuration). You can work around
restrictions like that by initializing the beans lazily when first used instead of on
initialization.
In the case of Filters
and Servlets
, you can also add mappings and init parameters by
adding a FilterRegistrationBean
or a ServletRegistrationBean
instead of or in
addition to the underlying component.
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If no If you are migrating a filter that has no @Bean public FilterRegistrationBean myFilterRegistration() { FilterRegistrationBean registration = new FilterRegistrationBean(); registration.setDispatcherTypes(DispatcherType.REQUEST); .... return registration; } |
As described above, any Servlet
or Filter
beans are registered with the servlet container automatically. To disable
registration of a particular Filter
or Servlet
bean, create a registration bean for it
and mark it as disabled, as shown in the following example:
@Bean public FilterRegistrationBean registration(MyFilter filter) { FilterRegistrationBean registration = new FilterRegistrationBean(filter); registration.setEnabled(false); return registration; }
@WebServlet
, @WebFilter
, and @WebListener
annotated classes can be automatically
registered with an embedded servlet container by annotating a @Configuration
class
with @ServletComponentScan
and specifying the package(s) containing the components
that you want to register. By default, @ServletComponentScan
scans from the package
of the annotated class.
In a standalone application, the main HTTP port defaults to 8080
but can be set with
server.port
(for example, in application.properties
or as a System property). Thanks to
relaxed binding of Environment
values, you can also use SERVER_PORT
(for example, as an OS
environment variable).
To switch off the HTTP endpoints completely but still create a WebApplicationContext
,
use server.port=-1
. (Doing so is sometimes useful for testing.)
For more details, see “Section 27.4.4, “Customizing Embedded Servlet Containers””
in the ‘Spring Boot features’ section, or the
ServerProperties
source
code.
To scan for a free port (using OS natives to prevent clashes) use server.port=0
.
You can access the port the server is running on from log output or from the
ServletWebServerApplicationContext
through its EmbeddedWebServer
. The best way to get
that and be sure that it has been initialized is to add a @Bean
of type
ApplicationListener<ServletWebServerInitializedEvent>
and pull the container
out of the event when it is published.
Tests that use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT)
can
also inject the actual port into a field by using the @LocalServerPort
annotation, as
shown in the following example:
@RunWith(SpringJUnit4ClassRunner.class) @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT) public class MyWebIntegrationTests { @Autowired ServletWebServerApplicationContext server; @LocalServerPort int port; // ... }
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SSL can be configured declaratively by setting the various server.ssl.*
properties,
typically in application.properties
or application.yml
. The following example shows
setting SSL properties in applicaiton.properties
:
server.port=8443 server.ssl.key-store=classpath:keystore.jks server.ssl.key-store-password=secret server.ssl.key-password=another-secret
See Ssl
for details of all of the
supported properties.
Using configuration such as the preceding example means the application no longer supports
a plain HTTP connector at port 8080. Spring Boot does not support the configuration of both
an HTTP connector and an HTTPS connector through application.properties
. If you want to
have both, you need to configure one of them programmatically. We recommend
using application.properties
to configure HTTPS, as the HTTP connector is the easier of
the two to configure programmatically. See the
spring-boot-sample-tomcat-multi-connectors
sample project for an example.
You can enable HTTP/2 support in your Spring Boot application with the
server.http2.enabled
configuration property. This support depends on the chosen web
server and the application environment, since that protocol is not supported
out-of-the-box by JDK8.
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Spring Boot does not support |
Currently, only Undertow and Tomcat are supported with this configuration key.
As of Undertow 1.4.0+, HTTP/2 is supported without any additional requirement on JDK8.
Spring Boot ships by default with Tomcat 8.5.x; with that version, HTTP/2 is only
supported if the libtcnative
library and its dependencies are installed on the host
operating system.
The library folder must be made available, if not already, to the JVM library path; this
can be done with a JVM argument such as
-Djava.library.path=/usr/local/opt/tomcat-native/lib
. More on this in the
official Tomcat documentation.
Starting Tomcat 8.5.x without that native support will log the following error:
ERROR 8787 --- [ main] o.a.coyote.http11.Http11NioProtocol : The upgrade handler [org.apache.coyote.http2.Http2Protocol] for [h2] only supports upgrade via ALPN but has been configured for the ["https-jsse-nio-8443"] connector that does not support ALPN.
This error is not fatal, and the application starts with HTTP/1.1 SSL support still.
Running your application with Tomcat 9.0.x and JDK9 doesn’t require any native library
installed. To use Tomcat 9, you can override the tomcat.version
build property with the
version of your choice.
Access logs can be configured for Tomcat, Undertow, and Jetty through their respective namespaces.
For instance, the following settings log access on Tomcat with a custom pattern.
server.tomcat.basedir=my-tomcat server.tomcat.accesslog.enabled=true server.tomcat.accesslog.pattern=%t %a "%r" %s (%D ms)
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The default location for logs is a |
Access logging for undertow can be configured in a similar fashion, as shown in the following example:
server.undertow.accesslog.enabled=true server.undertow.accesslog.pattern=%t %a "%r" %s (%D ms)
Logs are stored in a logs
directory relative to the working directory of the
application. You can customize this location by setting the
server.undertow.accesslog.directory
property.
Finally, access logging for Jetty can also be configured as follows:
server.jetty.accesslog.enabled=true server.jetty.accesslog.filename=/var/log/jetty-access.log
By default, logs are redirected to System.err
. For more details, see
the documentation.
Your application might need to send 302
redirects or render content with absolute links
back to itself. When running behind a proxy, the caller wants a link to the proxy and not
to the physical address of the machine hosting your app. Typically, such situations are
handled through a contract with the proxy, which adds headers to tell the back end how to
construct links to itself.
If the proxy adds conventional X-Forwarded-For
and X-Forwarded-Proto
headers (most
proxy server do so), the absolute links should be rendered correctly, provided
server.use-forward-headers
is set to true
in your application.properties
.
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If your application runs in Cloud Foundry or Heroku, the
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If you use Tomcat, you can additionally configure the names of the headers used to carry “forwarded” information, as shown in the following example:
server.tomcat.remote-ip-header=x-your-remote-ip-header server.tomcat.protocol-header=x-your-protocol-header
Tomcat is also configured with a default regular expression that matches internal
proxies that are to be trusted. By default, IP addresses in 10/8
, 192.168/16
,
169.254/16
and 127/8
are trusted. You can customize the valve’s configuration by
adding an entry to application.properties
, as shown in the following example:
server.tomcat.internal-proxies=192\\.168\\.\\d{1,3}\\.\\d{1,3}
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The double backslashes are required only when you use a properties file for
configuration. If you use YAML, single backslashes are sufficient, and a value
equivalent to that shown in the preceding example would be |
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You can trust all proxies by setting the |
You can take complete control of the configuration of Tomcat’s RemoteIpValve
by
switching the automatic one off (to do so, set server.use-forward-headers=false
) and adding
a new valve instance in a TomcatServletWebServerFactory
bean.
Generally, you can follow the advice from
“Section 73.8, “Discover Built-in Options for External Properties”” about
@ConfigurationProperties
(ServerProperties
is the main one here). However, you should
also look at ServletWebServerFactoryCustomizer
and various Tomcat-specific
*Customizers
that you can add. The Tomcat APIs are quite rich, so, once you have
access to the TomcatServletWebServerFactory
, you can modify it in a number of ways.
Alternatively, if you need more control and customization, you can add your own
TomcatServletWebServerFactory
.
You can add an org.apache.catalina.connector.Connector
to the
TomcatServletWebServerFactory
, which can allow multiple connectors, including HTTP and
HTTPS connectors, as shown in the following example:
@Bean public ServletWebServerFactory servletContainer() { TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory(); tomcat.addAdditionalTomcatConnectors(createSslConnector()); return tomcat; } private Connector createSslConnector() { Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol"); Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler(); try { File keystore = new ClassPathResource("keystore").getFile(); File truststore = new ClassPathResource("keystore").getFile(); connector.setScheme("https"); connector.setSecure(true); connector.setPort(8443); protocol.setSSLEnabled(true); protocol.setKeystoreFile(keystore.getAbsolutePath()); protocol.setKeystorePass("changeit"); protocol.setTruststoreFile(truststore.getAbsolutePath()); protocol.setTruststorePass("changeit"); protocol.setKeyAlias("apitester"); return connector; } catch (IOException ex) { throw new IllegalStateException("can't access keystore: [" + "keystore" + "] or truststore: [" + "keystore" + "]", ex); } }
By default, the embedded Tomcat used by Spring Boot does not support "Version 0" of the Cookie format, so you may see the following error:
java.lang.IllegalArgumentException: An invalid character [32] was present in the Cookie value
If at all possible, you should consider updating your code to only store values
compliant with later Cookie specifications. If, however, you cannot change the
way that cookies are written, you can instead configure Tomcat to use a
LegacyCookieProcessor
. To switch to the LegacyCookieProcessor
, use an
ServletWebServerFactoryCustomizer
bean that adds a TomcatContextCustomizer
, as shown
in the following example:
@Bean public WebServerFactoryCustomizer<TomcatServletWebServerFactory> cookieProcessorCustomizer() { return (serverFactory) -> serverFactory.addContextCustomizers( (context) -> context.setCookieProcessor(new LegacyCookieProcessor())); }
Generally you can follow the advice from
“Section 73.8, “Discover Built-in Options for External Properties”” about
@ConfigurationProperties
(ServerProperties
and ServerProperties.Undertow
are the
main ones here). However, you should also look at ServletWebServerFactoryCustomizer
.
Once you have access to the UndertowServletWebServerFactory
, you can use an
UndertowBuilderCustomizer
to modify Undertow’s configuration to meet your needs.
Alternatively, if you need more control and customization, you can add your own
UndertowServletWebServerFactory
.
Add an UndertowBuilderCustomizer
to the UndertowServletWebServerFactory
and
add a listener to the Builder
, as shown in the following example:
@Bean public UndertowServletWebServerFactory servletWebServerFactory() { UndertowServletWebServerFactory factory = new UndertowServletWebServerFactory(); factory.addBuilderCustomizers(new UndertowBuilderCustomizer() { @Override public void customize(Builder builder) { builder.addHttpListener(8080, "0.0.0.0"); } }); return factory; }
If you want to use @ServerEndpoint
in a Spring Boot application that used an embedded
container, you must declare a single ServerEndpointExporter
@Bean
, as shown in the
following example:
@Bean public ServerEndpointExporter serverEndpointExporter() { return new ServerEndpointExporter(); }
The bean shown in the preceding example registers any @ServerEndpoint
annotated beans
with the underlying WebSocket container. When deployed to a standalone servlet container,
this role is performed by a servlet container initializer, and the
ServerEndpointExporter
bean is not required.
HTTP response compression is supported by Jetty, Tomcat, and Undertow. It can be enabled
in application.properties
, as follows:
server.compression.enabled=true
By default, responses must be at least 2048 bytes in length for compression to be
performed. You can configure this behavior by setting the
server.compression.min-response-size
property.
By default, responses are compressed only if their content type is one of the following:
text/html
text/xml
text/plain
text/css
You can configure this behavior by setting the server.compression.mime-types
property.