ResponseBodyAdvice可以在注解@ResponseBody将返回值处理成相应格式之前操作返回值。实现这个接口即可完成相应操作。可用于对response 数据的一些统一封装或者加密等操作
1 ResponseBodyAdvice的简介
ResponseBodyAdvice接口和之前记录的RequestBodyAdvice接口类似, RequestBodyAdvice是请求到Controller之前拦截,做相应的处理操作, 而ResponseBodyAdvice是对Controller返回的{@code @ResponseBody}or a {@code ResponseEntity} 后,{@code HttpMessageConverter} 类型转换之前拦截, 进行相应的处理操作后,再将结果返回给客户端.
ResponseBodyAdvice的源代码:
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/** 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);} |
说明:
- supports方法: 判断是否要执行beforeBodyWrite方法,true为执行,false不执行. 通过该方法可以选择哪些类或那些方法的response要进行处理, 其他的不进行处理.
- beforeBodyWrite方法: 对response方法进行具体操作处理
{@code @ResponseBody} 返回响应体, 例如List集合
{@code ResponseEntity} 返回响应实体对象,例如User对象
2 ResponseBodyAdvice的使用
1 准备一个SpringBoot项目环境
2 添加一个响应拦截类
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@ControllerAdvicepublic 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); } }} |
3 添加一个返回包装类
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@Data@AllArgsConstructor@NoArgsConstructorpublic 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); }} |
4 添加控制类
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@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; }} |
5 接口测试
浏览器访问: http://localhost:8080/hello/one
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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 |
浏览器访问: http://localhost:8080/hello/list
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[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 |
ps: 如果直接响应字符串返回,则会报类型转换异常.
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原文链接：https://blog.csdn.net/ABestRookie/article/details/121003742
