Contents

1. 1. Spring如何对Controller的返回值进行统一格式化输出
   1. 1.1. 前言
   2. 1.2. 示例代码

Spring如何对Controller的返回值进行统一格式化输出

前言

Spring的RestController中，经常需要对返回值进行封装，将Java的VO或DTO对象封装为带code和message的响应结果。但是又不想每个方法都进行处理，类似：
Respose.success(data)。
可以使用Spring的ResponseBodyAdvice的接口对返回结果进行统一格式化输出，简化业务代码。

1. 新建一个自定义注解：

   @Target({ElementType.METHOD, ElementType.TYPE})
   @Retention(RetentionPolicy.RUNTIME)
   public @interface ApiResult {
   }
   

2. 新建一个公用的Result类：

   @Data
   public class Result<T> implements Serializable {
   
       private int code;
   
       private String message;
   
       private T data;
   }
   

3. 新建一个工厂方法ResultFactory，用来构造成功和失败的响应结果：

   @Component
   public class ResultFactory {
   
       public <T> Result<T> success(T data) {
           Result<T> result = new Result<>();
           result.setCode(ResultCode.SUCCESS.getCode());
           result.setData(data);
           return result;
       }
   
       public <T> Result<T> fail(T data) {
           Result<T> result = new Result<>();
           result.setCode(ResultCode.BAD_REQUEST.getCode());
           result.setData(data);
           return result;
       }
   }
   

4. 新建一个实现ResponseBodyAdvice的类，用来格式化输出：

   @ControllerAdvice
   public class GlobalResponseBodyAdvice implements ResponseBodyAdvice<Object> {
   @Resource
   private ResultFactory resultFactory;
   
       @Override
       public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
           return returnType.hasMethodAnnotation(ApiResult.class)
                   || returnType.getContainingClass().isAnnotationPresent(ApiResult.class);
       }
   
       @Override
       public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,
                                     Class<? extends HttpMessageConverter<?>> selectedConverterType,
                                     org.springframework.http.server.ServerHttpRequest request,
                                     org.springframework.http.server.ServerHttpResponse response) {
           if (body instanceof Result) {
               return body;
           }
   
           return resultFactory.success(body);
       }
   }
   

5. 在Controller的类上或方法上使用该注解：

   @ApiResult
   @RestController
   public class TestController {
   
       @PostMapping("/foo")
       public FooResult foo(@RequestBody @Valid FooCmd cmd) {
           FooEnum type = FooEnum.get(cmd.getValue());
           return new FooResult() {{
                   setCode(type.getCode());
                   setName(type.getValue());
               }};
       }
   }
   

6. 全局异常处理：

   @Slf4j
   @RestControllerAdvice
   public class GlobalExceptionHandler {
   @Resource
   private ResultFactory resultFactory;
   
       @ResponseBody
       @ExceptionHandler(MethodArgumentNotValidException.class)
       public ResponseEntity<Result<Map<String, String>>> handleMethodArgumentNotValidException(MethodArgumentNotValidException exception) {
           Map<String, String> errors = new HashMap<>();
           for (FieldError error : exception.getBindingResult().getFieldErrors()) {
               errors.put(error.getField(), error.getDefaultMessage());
           }
   
           Result<Map<String, String>> result = resultFactory.fail(errors);
           return new ResponseEntity<>(result, HttpStatus.BAD_REQUEST);
       }
   }
   

示例代码

完整示例代码：Spring format response