Spring Boot Profiles

We can externalize our spring boot configurations so that we can use the same code under different conditions or environments. One example would be to run the application on different ports to achieve zero-downtime deployment, or more specifically, a blue/green deployment strategy. We can externalize our configurations through application.properties or applications.yml files.

Spring Boot has a specific order of loading/overriding these property files, so we can use multiple configuration files for different purposes. Here is the overriding order, the top ones being higher in priority. You can find the full list on their docs.

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.
Default properties (specified by setting SpringApplication.setDefaultProperties).

For instance, let’s look at these two files.

# File: application.yml
server:
    port: 8080

# File: application-prod.yml
server:
    port: 8081

Since the application-{profile}.yml has higher precedence than the application.yml file, the 8081 value will override the default 8080 value.

Let’s say that we have another file, application-prod2.yml.

# File: application-prod2.yml
server:
    port: 8082

Now we must specify which profile to use. We can do this through system properties when executing the application.
java -jar -Dspring.profiles.active=prod2 myApplication.jar

The command above will activate the prod2 profile, so the application will run on port 8082.

We can also add other active profiles using the spring.profiles.include property. These profiles will always be activated on top of the main profile that was specified through the spring.profiles.active property.

You can find more info about externalized configuration and profiles on the Spring docs.

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