"required a single bean, but 2 were found" - Spring

Question

Here is my class:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.support.MessageSourceAccessor;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.util.Assert;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;

import com.mportal.ec.exception.ApplicationSpecificException;

@ControllerAdvice
public class DefaultExceptionHandler extends ResponseEntityExceptionHandler {

    @Autowired
    private final MessageSourceAccessor messageSource;


    public DefaultExceptionHandler(MessageSourceAccessor messageSource) {
        Assert.notNull(messageSource, "messageSource must not be null");
        this.messageSource = messageSource;
     }

      //expected Exceptions
      @ExceptionHandler(ApplicationSpecificException.class)
      protected ResponseEntity<Object> handleApplicationSpecificException(final RuntimeException ex, final WebRequest request) {
          final String bodyOfResponse = "This should be application specific";
          return handleExceptionInternal(ex, bodyOfResponse, new HttpHeaders(), HttpStatus.NOT_FOUND, request);
      }


      //unexpected Exceptions
      @ExceptionHandler(Exception.class)
        protected ResponseEntity<Object> handleException(final RuntimeException ex, final WebRequest request) {
          final String bodyOfResponse = "This should be application specific";
          return handleExceptionInternal(ex, bodyOfResponse, new HttpHeaders(), HttpStatus.INTERNAL_SERVER_ERROR, request);
      }
}

In my project, I'm using spring-boot/hibernate/ java based configuration and trying to implement an exception handling mechanism.I'm using an example code i got from StackOverflow and learn what's the best way to handle exceptions in spring. But when I run the code, I get this error. But when I stopped using "MessageSourceAccessor" the error goes away.

Description:

Parameter 0 of constructor in com.mportal.ec.error.DefaultExceptionHandler required a single bean, but 2 were found:
    - linkRelationMessageSource: defined by method 'linkRelationMessageSource' in class path resource [org/springframework/hateoas/config/HateoasConfiguration.class]
    - resourceDescriptionMessageSourceAccessor: defined by method 'resourceDescriptionMessageSourceAccessor' in class path resource [org/springframework/data/rest/webmvc/config/RepositoryRestMvcConfiguration.class]


Action:

Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

How do I resolve this?

Answer 1

You are using both constructor injection and field injection.

public DefaultExceptionHandler(MessageSourceAccessor messageSource) {
    Assert.notNull(messageSource, "messageSource must not be null");
    this.messageSource = messageSource;
 }

and

   @Autowired
   private final MessageSourceAccessor messageSource;

Choose only one.