java - 如何更好地处理@RequestParam(required=true)

Question

在springmvc项目的controller中，代码为:

@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;
    }

在我的浏览器上，我输入 http://localhost:8080/file_server/detail/add_detail 然后收到消息:HTTP Status 400 - Required String parameter 'versionId' is not present 。哦代码@RequestParam(required=true)String versionId起到了作用。但是有没有合适的方法，这种情况下返回json给前端？

Answer 1

(OPTION 1)如果你想改变返回到前端，你可以实现自定义org.springframework.boot.autoconfigure.web.ErrorController

例如:

@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;
    }

}

你现在总是会得到类似这样的 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"
}

如果你愿意，可以随意定制它。只需更改 Controller 中的错误方法即可。

---

(选项 2) 在您的 Controller 中使用自定义 @ExceptionHandler。可以阅读此以获取更多信息 https://spring.io/blog/2013/11/01/exception-handling-in-spring-mvc

只需在您的 FileDetailController 中添加类似的内容

@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);
}