ResponseAdvice not getting triggered

Question

Plenty of question in SO but almost no working solution.

Just a simple implementation of ResponseAdvice with @ControllerAdvice

Controller

@RestController
@ReqeustMapping("/test")
class TestController{
   @RequestMapping( method=GET )
   public String test(){ return "Test"; }
}

Advice

@RestControllerAdvice
public class ResponseDecorator implements ResponseBodyAdvice<String> {

    @Autowired
    ObjectMapper mapper;

    @Override
    public boolean supports(MethodParameter returnType,
                            Class<? extends HttpMessageConverter<?>> converterType) {
        return returnType.getParameterType().equals(String.class);
    }

    @Override
    public String beforeBodyWrite(String body,
                                  MethodParameter returnType,
                                  MediaType selectedContentType,
                                  Class<? extends HttpMessageConverter<?>> selectedConverterType,
                                  ServerHttpRequest request,
                                  ServerHttpResponse response) {
      System.out.println ( "Just print this when before sending ");
     return body;
   }
}

The beforeBodyWrite does not trigger at all. The app is fully annotation driven. And both advice and controller are in same package. What am I missing!

Answer 1

Ok. Silly mistake.The issue here is the supports methods

  @Override
    public boolean supports(MethodParameter returnType,
                            Class<? extends HttpMessageConverter<?>> converterType) {
        return returnType.getParameterType().equals(String.class);
    }

making this method return TRUE has fixed the issue.

  @Override
    public boolean supports(MethodParameter returnType,
                            Class<? extends HttpMessageConverter<?>> converterType) {
        return true;
    }

The supports method should return true. So adjust your logic based on your requirement.