浅析@ResponseBodyAdvice的理解以及实际应用

一、@ResponseBodyAdvice的理解

1、ResponseBodyAdvice接口类  ——  其描述大致解释下：

　　允许在执行{@code@ResponseBody}或{@code ResponseEntity}控制器方法之后，但在使用{@code HttpMessageConverter}编写主体之前自定义响应。

　　实现可以直接用{@code RequestMappingHandlerAdapter}和{@code exceptionhandleexceptionresolver}注册，或者更可能用{@code@ControllerAdvice}注释，在这种情况下，它们将被两者自动检测。

/** * 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}. * * 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.*/
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 * @param converterType the selected converter type * @return {@code true} if {@link #beforeBodyWrite} should be invoked; * {@code false} otherwise */
    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 */ T beforeBodyWrite(T body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response); }

2、个人理解：

　　ResponseBodyAdvice 接口是在 Controller 执行 return 之后，在 response 返回给客户端之前，执行的对 response 的一些处理，可以实现对 response 数据的一些统一封装或者加密等操作。

　　该接口一共有两个方法：

（1）supports  —— 判断是否要执行beforeBodyWrite方法，true为执行，false不执行  ——  通过supports方法，我们可以选择哪些类或哪些方法要对response进行处理，其余的则不处理。

（2）beforeBodyWrite  ——  对 response 处理的具体执行方法。

二、实例

　　有一个Controller类，返回参数为OutputObject，我们通过ResponseBodyAdvice，对该类的所有方法返回的OutputObject中的部分数据进行统一加密处理。

// 对响应报文统一处理，对bean内容进行加密 @Component //声明该类要处理的包路径
@ControllerAdvice("com.cmos.edcreg.web.controller") public class ResponseAdvice implements ResponseBodyAdvice { private final Logger logger = LoggerFactory.getLogger(ResponseAdvice.class); // 对response处理的具体方法 @Override public Object beforeBodyWrite(Object arg0, MethodParameter arg1, MediaType arg2, Class arg3, ServerHttpRequest arg4, ServerHttpResponse arg5) { OutputObject out = new OutputObject(); try { //arg0转换为OutputObject类型
            ObjectMapper objectMapper=new ObjectMapper(); out = objectMapper.readValue(org.json.JSONObject.valueToString(arg0), OutputObject.class); //获取加密密钥
            String oldEncryptKey = out.getBean().get("oldEncryptKey"); //获取加密字符串
            DesSpecial des = new DesSpecial(); String encryptData = des.strEnc(JSON.toJSONString(out.getBean()), oldEncryptKey, null, null); //封装数据（清除原来数据，放入加密数据）
 out.getBean().clear(); out.getBean().put("data", encryptData); return out; } catch (Exception e) { logger.error("返回报文处理出错", e); out.setReturnCode(ReturnInfoEnums.PROCESS_ERROR.getCode()); out.setReturnMessage(ReturnInfoEnums.PROCESS_ERROR.getMessage()); return out; } } /* 选择哪些类，或哪些方法需要走beforeBodyWrite * 从arg0中可以获取方法名和类名 * arg0.getMethod().getDeclaringClass().getName()为获取方法名 */ @Override public boolean supports(MethodParameter arg0, Class arg1) { return "com.cmos.edcreg.web.controller.GdH5AppointmentActiveVideoNewController".equals(arg0.getMethod().getDeclaringClass().getName()); } }

三、在spring项目开发过程中的应用场景

　　对controller层返回值进行修改增强处理。比如返回值5，需要封装成：{"code":"0","data":5,,"msg":"success"} 格式返回前端

1、controller层业务代码

@RestController //此注解包含@ResponseBody注解
@RequestMapping("/mp") public class ResponseBodyAdviceController { @RequestMapping(value = "/hello", method = RequestMethod.GET) public int hello() {
        return 5; } }

2、实现ResponseBodyAdvice接口的切面类

/** *此注解针对controller层的类做增强功能，即对加了@RestController注解的类进行处理 */ @ControllerAdvice(annotations = RestController.class) public class RestResultWrapper implements ResponseBodyAdvice<Object> { @Override public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) { return true; } @Override public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) { //定义一个统一的返回类
            RestResult responseResult = new RestResult( "0", body, "success"); //如果handler处理类的返回类型是String（即控制层的返回值类型），为了保证一致性，这里需要将ResponseResult转回去
            if(body instanceof String) { return JSON.toJSONString(responseResult); } //封装后的数据返回到前端页面
            return JSONObject.toJSON(responseResult); } }

3、返回公共类的创建

// 统一返回Rest风格的数据结构
public class RestResult<T>  implements Serializable { private String code = "2000"; // 成功时返回的数据，失败时返回具体的异常信息
    private T data; // 请求失败返回的提示信息，给前端进行页面展示的信息
    private String message ; public RestResult() { } @Override public String toString() { return "RestResult{" +
                "code='" + code + '\'' +
                ", data=" + data +
                ", message=" + message +
                '}'; } public RestResult(String code, T data, String message) { this.code = code; this.data = data; this.message = message; } }