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javaspringspring-bean

Spring choose bean implementation at runtime

I'm using Spring Beans with annotations and I need to choose different implementation at runtime.

@Service
public class MyService {
   public void test(){...}
}

For example for windows's platform I need MyServiceWin extending MyService, for linux platform I need MyServiceLnx extending MyService.

For now I know only one horrible solution:

@Service
public class MyService {

    private MyService impl;

   @PostInit
   public void init(){
        if(windows) impl=new MyServiceWin();
        else impl=new MyServiceLnx();
   }

   public void test(){
        impl.test();
   }
}

Please consider that I'm using annotation only and not XML config.

Solution

  • 1. Implement a custom Condition

    public class LinuxCondition implements Condition {
  @Override
  public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
    return context.getEnvironment().getProperty("os.name").contains("Linux");  }
}

    Same for Windows.

    2. Use @Conditional in your Configuration class

    @Configuration
public class MyConfiguration {
   @Bean
   @Conditional(LinuxCondition.class)
   public MyService getMyLinuxService() {
      return new LinuxService();
   }

   @Bean
   @Conditional(WindowsCondition.class)
   public MyService getMyWindowsService() {
      return new WindowsService();
   }
}

    3. Use @Autowired as usual

    @Service
public class SomeOtherServiceUsingMyService {

    @Autowired    
    private MyService impl;

    // ... 
}