Springboot(HandlerMethodReturnValueHandler使用) 自定义注解处理返回值

曾经终败给现在 2022-10-17 04:28 313阅读 0赞

在我们开发接口的时候我想到大多数接口都需要返回如下格式

{ 
        "code": "200",
        "data":"",
        "msg": "success"
    }

大多人的做法其实很简单，但是也很冗余

开发一个 ResponseResult,然后返回对象用这个对象包起来，大概长这么个样子

@GetMapping("/test")
        public ResponseResult test() { 
        List<Student> students;
    	ResponseUtils.success(students)
    	}

而 ResponseResult 中则是如下代码

return new ResponseResult(ErrorCodeConstants.SUCCESS, null, data);
    
    @Data
    @AllArgsConstructor
    public  class ResponseResult<T> { 
        private Integer code;
        private String msg;
        private T data;
    
        public boolean success() { 
            return this.code == ResultCodeMeg.SUCCESS.getCode();
        }
    }

每次返回我们都需要去调用 ResponseUtils.success方法，有没有办法干掉这个方法直接返回我们数据类 students，而要求满足前端的呢，我们可以基于 HandlerMethodReturnValueHandler 来实现

首先自定义一个返回注解

@Target({ ElementType.TYPE, ElementType.METHOD})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface ZouResponseBody { 
    	//序列化方式
        SerializerFeature[] serializerFeature() default { };
    }

> ps 这里依赖了 fastjson

在自定义返回类

*  ZouBaseResponse.class

@Data
    public class ZouBaseResponse implements Serializable { 
        private String code;
        private String msg;
        private Object data;
    }

自定义 返回值处理配置类 实现 HandlerMethodReturnValueHandler接口

*  ZouResponseBodyHandleReturnValue.class

public class ZouResponseBodyHandleReturnValue implements HandlerMethodReturnValueHandler, AsyncHandlerMethodReturnValueHandler { 
    
    
        @Override
        public boolean isAsyncReturnValue(Object returnValue, MethodParameter returnType) { 
            return supportsReturnType(returnType);
        }
    	
    	// 如果被 ZouResponseBody.class 注解修饰则处理
        @Override
        public boolean supportsReturnType(MethodParameter returnType) { 
            return returnType.getParameterType() != ZouBaseResponse.class
                    && !ObjectUtils.isEmpty(returnType.getAnnotatedElement().getAnnotation(ZouResponseBody.class));
    
        }
    	
    	// 返回值封装
        @Override
        public void handleReturnValue(Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception { 
            mavContainer.setRequestHandled(true);
            HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
            assert response != null;
            response.setContentType("application/json;charset=utf-8");
            ZouBaseResponse baseResponse = new ZouBaseResponse();
            baseResponse.setCode("200");
            baseResponse.setMsg("success");
            baseResponse.setData(returnValue);
            ZouResponseBody responseBody = returnType.getAnnotatedElement().getAnnotation(ZouResponseBody.class);
            SerializerFeature[] defaultSerializerFeature = { 
                    SerializerFeature.DisableCircularReferenceDetect
            };
            /** * 替换注解中的序列化格式 */
            if (!ObjectUtils.isEmpty(responseBody) && !ObjectUtils.isEmpty(responseBody.serializerFeature())) { 
                defaultSerializerFeature = responseBody.serializerFeature();
            }
            response.getWriter().write(JSON.toJSONString(baseResponse, defaultSerializerFeature));
    
        }
    }

定义一个WebMVC 配置类 加入自定义的处理器 ZouResponseBodyHandleReturnValue

@Configuration
    public class WebMvcConfig implements WebMvcConfigurer { 
    
        @Override
        public void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) { 
            returnValueHandlers.add(new ZouResponseBodyHandleReturnValue());
        }
    }

## 使用测试 ##

@RestController
    @RequestMapping("/user")
    public class UserController { 
    
        @ZouResponseBody
        @GetMapping("/user")
        public List<Student> getUsers() { 
            Student student = new Student();
            student.setName("小奏");
            student.setAge(22);
            Student student1 = new Student();
            student.setName("小明");
            student.setAge(23);
            return Lists.newArrayList(student, student1);
        }
    
    }

返回结果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNjUxOTA0_size_16_color_FFFFFF_t_70]

> 使用起来要比原先的那种方式更为简洁

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNjUxOTA0_size_16_color_FFFFFF_t_70]: /images/20221014/955eb923c4024e37a03fa4955acc7430.png