如何修复外部jar导入中的Autowired

Question

I'm having a well working library and I would like to utilize the library in one of my sample Spring boot console application.

I built the library using the command mvn clean install and the newly generated .jar file I imported in my sample Spring boot console application.

I created a bean in my new sample application and tried to create an object of UserManagementService , which is in the external .jar and the said jar internally has two properties

External Jar's - Service file

public class UserManagementService {

    @Autowired
    UserService userService;

    @Autowired
    ManagementService managementService;

    public String getUserFirstName(String userName) {
        return userService.getUserFirstName(userName);
    }


    .. Rest of the implementation
}

These two autowired is not working and it has the value null moreover it throws an exception org.springframework.beans.factory.BeanDefinitionStoreException: Failed to parse configuration class...

My Sample Application:

public class ApplicationBean {

    private UserManagementService userService = new UserManagementService();

    public void run() {
        if(userService == null) {
            System.out.println("Oops");
        }

        String userFirstName = userService.getUserFirstName("Emma");
        ... Rest of the implementation
    }
}

Kindly assist me how to fix this.

Answer 1

You need to declare your user management service as a bean in order to be able to inject it.

First Approach Annotate the UserManagementService class with @Service if you have control over the library, UserService and ManagementService needs to be annotated with @Service too so they can be injected into UserManagementService . You may need to use @ComponentScan(basePackages = { "libray.package" }) in your spring app (over main class) to make it scan your library and load the services.

Second Approach You make your library framework independent and make UserManagementService a simple POJO where you pass UserService and ManagementService as constructor arguments, then declare those beans in your spring app

public class ApplicationBean {
  @Bean
  public UserService userServiceProvider(){
  return new UserService();
  }
  @Bean
  public ManagementService managementServiceProvider(){
  return new ManagementService();
  }
  @Bean
  public UserManagementService userManagementServiceProvider(UserService userService, ManagementService managementService){
  return new UserManagementService(userService, managementService);
  }
}

These beans declaration go to application main class or to a class annotated with @Configuration