淺析@ResponseBodyAdvice的理解以及實際應用

一、@ResponseBodyAdvice的理解

1、ResponseBodyAdvice接口類  ——  其描述大致解釋下：

　　允許在執行{@code@ResponseBody}或{@code ResponseEntity}控制器方法之后，但在使用{@code HttpMessageConverter}編寫主體之前自定義響應。

　　實現可以直接用{@code RequestMappingHandlerAdapter}和{@code exceptionhandleexceptionresolver}注冊，或者更可能用{@code@ControllerAdvice}注釋，在這種情況下，它們將被兩者自動檢測。

/** * 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、個人理解：

　　ResponseBodyAdvice 接口是在 Controller 執行 return 之后，在 response 返回給客戶端之前，執行的對 response 的一些處理，可以實現對 response 數據的一些統一封裝或者加密等操作。

　　該接口一共有兩個方法：

（1）supports  —— 判斷是否要執行beforeBodyWrite方法，true為執行，false不執行  ——  通過supports方法，我們可以選擇哪些類或哪些方法要對response進行處理，其余的則不處理。

（2）beforeBodyWrite  ——  對 response 處理的具體執行方法。

二、實例

　　有一個Controller類，返回參數為OutputObject，我們通過ResponseBodyAdvice，對該類的所有方法返回的OutputObject中的部分數據進行統一加密處理。

// 對響應報文統一處理，對bean內容進行加密 @Component //聲明該類要處理的包路徑
@ControllerAdvice("com.cmos.edcreg.web.controller") public class ResponseAdvice implements ResponseBodyAdvice { private final Logger logger = LoggerFactory.getLogger(ResponseAdvice.class); // 對response處理的具體方法 @Override public Object beforeBodyWrite(Object arg0, MethodParameter arg1, MediaType arg2, Class arg3, ServerHttpRequest arg4, ServerHttpResponse arg5) { OutputObject out = new OutputObject(); try { //arg0轉換為OutputObject類型
            ObjectMapper objectMapper=new ObjectMapper(); out = objectMapper.readValue(org.json.JSONObject.valueToString(arg0), OutputObject.class); //獲取加密密鑰
            String oldEncryptKey = out.getBean().get("oldEncryptKey"); //獲取加密字符串
            DesSpecial des = new DesSpecial(); String encryptData = des.strEnc(JSON.toJSONString(out.getBean()), oldEncryptKey, null, null); //封裝數據（清除原來數據，放入加密數據）
 out.getBean().clear(); out.getBean().put("data", encryptData); return out; } catch (Exception e) { logger.error("返回報文處理出錯", e); out.setReturnCode(ReturnInfoEnums.PROCESS_ERROR.getCode()); out.setReturnMessage(ReturnInfoEnums.PROCESS_ERROR.getMessage()); return out; } } /* 選擇哪些類，或哪些方法需要走beforeBodyWrite * 從arg0中可以獲取方法名和類名 * arg0.getMethod().getDeclaringClass().getName()為獲取方法名 */ @Override public boolean supports(MethodParameter arg0, Class arg1) { return "com.cmos.edcreg.web.controller.GdH5AppointmentActiveVideoNewController".equals(arg0.getMethod().getDeclaringClass().getName()); } }

三、在spring項目開發過程中的應用場景

　　對controller層返回值進行修改增強處理。比如返回值5，需要封裝成：{"code":"0","data":5,,"msg":"success"} 格式返回前端

1、controller層業務代碼

@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、實現ResponseBodyAdvice接口的切面類

/** *此注解針對controller層的類做增強功能，即對加了@RestController注解的類進行處理 */ @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) { //定義一個統一的返回類
            RestResult responseResult = new RestResult( "0", body, "success"); //如果handler處理類的返回類型是String（即控制層的返回值類型），為了保證一致性，這里需要將ResponseResult轉回去
            if(body instanceof String) { return JSON.toJSONString(responseResult); } //封裝后的數據返回到前端頁面
            return JSONObject.toJSON(responseResult); } }

3、返回公共類的創建

// 統一返回Rest風格的數據結構
public class RestResult<T>  implements Serializable { private String code = "2000"; // 成功時返回的數據，失敗時返回具體的異常信息
    private T data; // 請求失敗返回的提示信息，給前端進行頁面展示的信息
    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; } }