SpringApplication has bean properties (mainly setters) so you can use its Java API as
you create the application to modify its behavior. Or you can externalize the
configuration using properties in
spring.main.*. E.g. in
and then the Spring Boot banner will not be printed on startup, and the application will not be a web application.
The example above also demonstrates how flexible binding allows the use of
By default properties from different sources are added to the Spring
Environment in a
defined order (see Chapter 23, Externalized Configuration in
the ‘Spring Boot features’ section for the exact order).
A nice way to augment and modify this is to add
@PropertySource annotations to your
application sources. Classes passed to the
SpringApplication static convenience
methods, and those added using
setSources() are inspected to see if they have
@PropertySources, and if they do, those properties are added to the
enough to be used in all phases of the
ApplicationContext lifecycle. Properties added
in this way have precedence over any added using the default locations, but have lower
priority than system properties, environment variables or the command line.
You can also provide System properties (or environment variables) to change the behavior:
SPRING_CONFIG_NAME), defaults to
applicationas the root of the file name.
SPRING_CONFIG_LOCATION) is the file to load (e.g. a classpath resource or a URL). A separate
Environmentproperty source is set up for this document and it can be overridden by system properties, environment variables or the command line.
No matter what you set in the environment, Spring Boot will always load
application.properties as described above. If YAML is used then files with the ‘.yml’
extension are also added to the list by default.
for more detail.
Some people like to use (for example)
--port=9000 instead of
set configuration properties on the command line. You can easily enable this by using
If you are inheriting from the
In this specific case the port binding will work in a PaaS environment like Heroku
and Cloud Foundry, since in those two platforms the
YAML is a superset of JSON and as such is a very convenient syntax for storing external properties in a hierarchical format. E.g.
spring: application: name: cruncher datasource: driverClassName: com.mysql.jdbc.Driver url: jdbc:mysql://localhost/test server: port: 9000
Create a file called
application.yml and stick it in the root of your classpath, and
snakeyaml to your dependencies (Maven coordinates
included if you use the
spring-boot-starter). A YAML file is parsed to a Java
Map<String,Object> (like a JSON object), and Spring Boot flattens the map so that it
is 1-level deep and has period-separated keys, a lot like people are used to with
Properties files in Java.
The example YAML above corresponds to an
spring.application.name=cruncher spring.datasource.driverClassName=com.mysql.jdbc.Driver spring.datasource.url=jdbc:mysql://localhost/test server.port=9000
See Section 23.6, “Using YAML instead of Properties” in the ‘Spring Boot features’ section for more information about YAML.
Environment has an API for this, but normally you would set a System profile
spring.profiles.active) or an OS environment variable (
launch your application with a
-D argument (remember to put it before the main class
or jar archive):
$ java -jar -Dspring.profiles.active=production demo-0.0.1-SNAPSHOT.jar
In Spring Boot you can also set the active profile in
A value set this way is replaced by the System property or environment variable setting,
but not by the
SpringApplicationBuilder.profiles() method. Thus the latter Java API can
be used to augment the profiles without changing the defaults.
See Chapter 24, Profiles in the ‘Spring Boot features’ section for more information.
A YAML file is actually a sequence of documents separated by
--- lines, and each
document is parsed separately to a flattened map.
If a YAML document contains a
spring.profiles key, then the profiles value
(comma-separated list of profiles) is fed into the Spring
Environment.acceptsProfiles() and if any of those profiles is active that document is
included in the final merge (otherwise not).
server: port: 9000 --- spring: profiles: development server: port: 9001 --- spring: profiles: production server: port: 0
In this example the default port is 9000, but if the Spring profile ‘development’ is active then the port is 9001, and if ‘production’ is active then it is 0.
The YAML documents are merged in the order they are encountered (so later values override earlier ones).
To do the same thing with properties files you can use
to specify profile-specific values.
Spring Boot binds external properties from
other places) into an application at runtime. There is not (and technically cannot be)
an exhaustive list of all supported properties in a single location because contributions
can come from additional jar files on your classpath.
A running application with the Actuator features has a
configprops endpoint that shows
all the bound and bindable properties available through
The appendix includes an
application.properties example with a list of the most common properties supported by
Spring Boot. The definitive list comes from searching the source code for
@Value annotations, as well as the occasional use of