[JAVA] How to set and use profile in annotation-based Configuration in Spring framework

Spring DI

Configuration

In the Spring framework, a configuration file called Configuration is passed to the DI container, and "Return this instance in such a case" is set. There are three types of Configuration files.

--Java-based Configuration --XML-based Configuration --Annotation-based Configuration

The annotation-based Configuration is described below.

Annotation-based Configuration

@Configuration Indicates that it is a Configuration class.

AppConfig

package com.example;

@Configuration
public class AppConfig {

}

@Component Register the class as a bean to be managed by the DI container.

User

package com.example;

@Component
public class User {

  public String getName(){
    ...
  }

}

@ComponentScan Scan the class with @Component and register it in DI as a bean. The scan target can be specified as a package. The settings for the AppConfig class mentioned earlier are as follows.

Configuration

package com.example;

@Configuration
@ComponentScan("com.example")
public class AppConfig {

}

Annotation-based Configuration sample code

If you use the DI container with the above annotations, the code will be as follows.

DemoIoC

package com.example;

public class DemoIoC {
  public static void main(String args[]){

    //Build a DI container and pass a Configuration file
    AnnotationConfigApplicationContext context =
                      new AnnotationConfigApplicationContext(AppConfig.class);

    //Get Bean
    User user = context.getBean(User.class);
    System.out.println(User.getName())
  }
}

Profile settings

In Spring framework, Configuration can be grouped and managed as a profile. For example, Configuration for development, Configuration for testing, and Configuration for products can be managed separately, and the Configuration can be easily switched.

@Profile Set the profile. Change the User class hierarchy as follows and set the profile.

User

package com.example;

public interface User {
  public String getName();
}

UserDummy

package com.example;

@Component
@Profile("dev") //Set profile with the name dev
public class UserDummy implements User {
  ...
}

UserMaster

package com.example;

@Component
@Profile("test") //Set profile with the name test
public class UserImpl implements User {
  ...
}

Profile usage example

Let's set a profile and use the above User class hierarchy.

DemoIoC

package com.example;

public class DemoIoC {
  public static void main(String args[]){

    //Build DI container
    //Set dev as profile
    AnnotationConfigApplicationContext context =
                      new AnnotationConfigApplicationContext();
    context.register(AppConfig.class);
    context.getEnvironment().addActiveProfile("dev");
    context.refresh();

    //Get Bean
    //The implementation of user is UserDummy
    User user = context.getBean(User.class);
    System.out.println(User.getName())
  }
}