How to configure Profiles in Spring Boot

#java #springboot #spring

First step is to create a project in Spring Initializer using the default values as shown in image. Or if you're integrating in your current project, you can go to the next step.
Create application.yaml file in your spring-boot project at location src/main/resources folder.
Now create a .yaml file for each profile we want to configure. For dev I'm naming my file application-dev.yaml, for staging application-staging.yaml
Now in your pom.xml file, copy the following lines

<profiles>
        <profile>
            <id>dev</id>
            <properties>
                <activatedProperties>dev</activatedProperties>
            </properties>
            <activation>
                <activeByDefault>true</activeByDefault>
            </activation>
        </profile>
        <profile>
            <id>staging</id>
            <properties>
                <activatedProperties>staging</activatedProperties>
            </properties>
        </profile>
</profiles>

Over here we're defining our two profiles dev and staging. The line <activeByDefault>true</activeByDefault> means that the profile dev will be active if no profile has been selected while running the spring boot project.

Now in the application.yaml file, put the following lines

spring:
  profiles:
    active: @activatedProperties@

This would be reading the <activatedProperties> tag in your pom.xml

In application-dev.yaml copy the following lines

spring:
  profiles: dev
server:
  port: 8093
application:
  current-profile: dev

In application-staging.yaml

spring:
  profiles: staging
server:
  port: 8094
application:
  current-profile: staging

Notice that the port property in application-dev.yaml and application-staging.yaml is different.
Now, to run the application using dev profile, run the command
mvn spring-boot:run -Dspring-boot.run.profiles=dev
and for staging
mvn spring-boot:run -Dspring-boot.run.profiles=staging
For dev, application will run on port 8093 and for staging, on 8094.
The advantage of using profiles is the we can configure different properties for different environments. Another advantage would be to use different variables in different environments. To show this we can create a class ActiveProfile.java in the application.
Copy the following lines

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

@Component
public class ActiveProfile {

    @Value("${application.current-profile}")
    private String profile;

    @EventListener(ContextRefreshedEvent.class)
    public void onStartUp() {
        System.out.println("The current profile is : " +  profile);
    }
}

Annotating onStartUp() function with @EventListener(ContextRefreshedEvent.class) means that, this function would run right after the application is ready.

@Value annotation will pick up the value from either application-dev.yaml or application-staging.yaml depending on which profile you run it with.