Spring中ResponseBodyAdvice的使用详解

/**   数据的处理顺序向下

  * Allows customizing the response after the execution of an {@code @ResponseBody}

  * or a {@code ResponseEntity} controller method but before the body is written

  * with an {@code HttpMessageConverter}.

  *

  * <p>Implementations may be registered directly with

  * {@code RequestMappingHandlerAdapter} and {@code ExceptionHandlerExceptionResolver}

  * or more likely annotated with {@code @ControllerAdvice} in which case they

  * will be auto-detected by both.

  *

  * @author Rossen Stoyanchev

  * @since 4.1

  * @param <T> the body type

  */

public interface ResponseBodyAdvice<T> {

     /**

      * Whether this component supports the given controller method return type

      * and the selected {@code HttpMessageConverter} type.

      * @param returnType the return type   方法返回的类型

      * @param converterType the selected converter type   参数类型装换

      * @return {@code true} if {@link #beforeBodyWrite} should be invoked;

      * {@code false} otherwise

      * 返回 true 则下面 beforeBodyWrite方法被调用, 否则就不调用下述方法

      */

     boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType);

     /**

      * Invoked after an {@code HttpMessageConverter} is selected and just before

      * its write method is invoked.

      * @param body the body to be written

      * @param returnType the return type of the controller method

      * @param selectedContentType the content type selected through content negotiation

      * @param selectedConverterType the converter type selected to write to the response

      * @param request the current request

      * @param response the current response

      * @return the body that was passed in or a modified (possibly new) instance

      */

     @Nullable

     T beforeBodyWrite( @Nullable T body, MethodParameter returnType, MediaType selectedContentType,

             Class<? extends HttpMessageConverter<?>> selectedConverterType,

             ServerHttpRequest request, ServerHttpResponse response);

}

@ControllerAdvice

public class BaseResponseBodyAdvice implements ResponseBodyAdvice<Object> {

     @Override

     public boolean supports(MethodParameter returnType, Class converterType) {

         return true ;

     }

     @Override

     public Object beforeBodyWrite(Object body, MethodParameter returnType,

             MediaType selectedContentType, Class selectedConverterType, ServerHttpRequest request,

             ServerHttpResponse response) {

         // 遇到feign接口之类的请求, 不应该再次包装,应该直接返回

         // 上述问题的解决方案: 可以在feign拦截器中,给feign请求头中添加一个标识字段, 表示是feign请求

         // 在此处拦截到feign标识字段, 则直接放行 返回body.

         System.out.println( "响应拦截成功" );

         if (body instanceof BaseResponse) {

             return body;

         } else if (body == null ) {

             return BaseResponse.ok();

         } else {

             return BaseResponse.ok(body);

         }

     }

}

@Data

@AllArgsConstructor

@NoArgsConstructor

public class BaseResponse<T> {

     private T data;

     private int status = 200 ;

     private String message;

     private long srvTime = System.currentTimeMillis();

     public BaseResponse(String message) {

         this .message = message;

     }

     public BaseResponse<T> setData(T data) {

         this .data = data;

         return this ;

     }

     public static <T> BaseResponse<T> ok() {

         return new BaseResponse<>( "操作成功" );

     }

     public static <T> BaseResponse<T> ok(T data) {

         return new BaseResponse<T>( "操作成功" ).setData(data);

     }

}

@Controller

@RequestMapping ( "/hello" )

public class HelloWorld {

     // 此处数据从数据库中查询, 案例中也可以使用伪数据代替

     @Autowired

     private UserMapper userMapper;

     // {@code ResponseEntity} 案列

     @GetMapping ( "/one" )

     @ResponseBody

     public User one() {

         List<User> users = userMapper.selectAll();

         System.out.println(users.get( 0 ));

         return users.get( 0 );

     }

     // {@code @ResponseBody}  案列

     @GetMapping ( "/list" )

     @ResponseBody

     public List<User> list() {

         List<User> users = userMapper.selectAll();

         System.out.println(users);

         return users;

     }

}   

User(id= 1 , username=李子柒, phone= 77777 , icon=李子柒的头像, queryTime=Wed Oct 27 20 : 47 : 02 CST 2021 )

响应拦截成功

[User(id= 1 , username=李子柒, phone= 77777 , icon=李子柒的头像, queryTime=Wed Oct 27 20 : 46 : 58 CST 2021 )]

响应拦截成功