How to deal with the @RequestParam(required=true) better

Question

When in the controller of the springmvc project, the code is:

@Controller
@RequestMapping("/detail")
public class FileDetailController {
    @RequestMapping("/add_detail")
    @ResponseBody
    public Object addDetailWithVersionId(@RequestParam(required=true)String versionId, 
        String description) {

        if(hasVersion(versionId)) {
            FileDetail fileDetail = new FileDetail();
            fileDetail.setId(UUIDUtil.getUUID());
            fileDetail.setDescription(description);
            fileDetail.setVersionId(versionId);
           // detailService.insert(fileDetail);
            return JsonUtil.SUCCESS;
        }
        return JsonUtil.ERROR;
    }

On my browser, I input http://localhost:8080/file_server/detail/add_detail and then get message: HTTP Status 400 - Required String parameter 'versionId' is not present. Oh the code @RequestParam(required=true)String versionId played a role in. But Is there a suitable method, return json to front-end in this case?

Answer 1

(OPTION 1) If you want to change return to frontend, you can implement custom org.springframework.boot.autoconfigure.web.ErrorController

For example with:

@RestController
public class MyErrorController extends AbstractErrorController {

    private static final String PATH = "/error";

    @Autowired
    public MyErrorController(ErrorAttributes errorAttributes) {
        super(errorAttributes);
    }

    @RequestMapping(value = PATH)
    public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
        Map<String, Object> body = getErrorAttributes(request, false);
        HttpStatus status = getStatus(request);
        return new ResponseEntity<Map<String, Object>>(body, status);
    }

    @Override
    public String getErrorPath() {
        return PATH;
    }

}

you will now always get something like this json:

{
  "timestamp": 1462600073772,
  "status": 400,
  "error": "Bad Request",
  "exception": "org.springframework.web.bind.MissingServletRequestParameterException",
  "message": "Required String parameter 'versionId' is not present",
  "path": "/add_detail"
}

can customize it whatever you like if you want to. Just change error method in controller.

---

(OPTION 2) Use custom @ExceptionHandler in your controller. Can read this for more info https://spring.io/blog/2013/11/01/exception-handling-in-spring-mvc

Just add something like this in your FileDetailController

@Autowired
private ErrorAttributes errorAttributes;

@ExceptionHandler(MissingServletRequestParameterException.class)
public ResponseEntity<Map<String, Object>> handle(HttpServletRequest request, Exception exception) {
    RequestAttributes requestAttributes = new ServletRequestAttributes(request);
    Map body = this.errorAttributes.getErrorAttributes(requestAttributes,false);

    return new ResponseEntity<Map<String, Object>>(body, HttpStatus.BAD_REQUEST);
}