SpringMVC | Controller 返回值及异常的统一处理

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发布于: 3 小时前

旧的设计方案

开发 api 的时候,需要先定义好接口的数据响应结果.如下是一个很简单直接的 Controller 实现方法及响应结果定义.

@RestController@RequestMapping("/users")public class UserController {
  @Inject  private UserService userService;
  @GetRequest("/{userId:\\d+}")  public ResponseBean signin(@PathVariable long userId) {    try {      User user = userService.getUserBaseInfo(userId);      return ResponseBean.success(user);    } catch (ServiceException e) {      return new ReponseBean(e.getCode(), e.getMsg());    } catch (Exception e) {      return ResponseBean.systemError();    }  }}

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{  code: "",  data: {}, // 可以是对象或者数组  msg: ""}

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从上面的代码，我们可以看到对于每个 Controller 方法，都会有很多重复的代码出现，我们应该设法去避免重复的代码。将重复的代码移除之后，可以得到如下的代码，简单易懂。

@RestController@RequestMapping("/users")public class UserController {          @Inject  private UserService userService;
    @GetRequest("/{userId:\\d+}")  public User signin(@PathVariable long userId) {        return userService.getUserBaseInfo(userId);  }}

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在以上的实现中，还做了一个必要的要求，就是 ServiceException 需要定义为 RuntimeException的子类，而不是 Exception的子类。由于 ServiceException 表示服务异常，一般发生这种异常是应该直接提示前端，而无需进行其他特殊处理的。在定义为 RuntimeException 的子类之后，会减少大量的异常抛出声明，而且不再需要在事务@Transactional 中进行特殊声明。

统一 Controller 返回值格式

在开发的过程中，我发现上面的结构

@ControllerAdvicepublic class ControllerResponseHandler implements ResponseBodyAdvice<Object> {    private Logger logger = LogManager.getLogger(getClass());
  @Override  public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {    // 支持所有的返回值类型    return true;  }
  @Override  public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,      Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request,      ServerHttpResponse response) {    if(body instanceof ResponseBean) {      return body;    } else {      // 所有没有返回　ResponseBean　结构的结果均认为是成功的      return ResponseBean.success(body);    }  }}

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统一异常处理

如下的代码中，ServiceException ServiceMessageException ValidatorErrorType FieldValidatorError 均为自定义类。

@ControllerAdvicepublic class ControllerExceptionHandler {
  private Logger logger = LogManager.getLogger(getClass());
  private static final String logExceptionFormat = "[EXIGENCE] Some thing wrong with the system: %s";
  /**   * 自定义异常   */  @ExceptionHandler(ServiceMessageException.class)  public ResponseBean handleServiceMessageException(HttpServletRequest request, ServiceMessageException ex) {    logger.debug(ex);    return new ResponseBean(ex.getMsgCode(), ex.getMessage());  }
  /**   * 自定义异常   */  @ExceptionHandler(ServiceException.class)  public ResponseBean handleServiceException(HttpServletRequest request, ServiceException ex) {    logger.debug(ex);    String message = codeToMessage(ex.getMsgCode());    return new ResponseBean(ex.getMsgCode(), message);  }
  /**   * MethodArgumentNotValidException: 实体类属性校验不通过   * 如: listUsersValid(@RequestBody @Valid UserFilterOption option)   */  @ExceptionHandler(MethodArgumentNotValidException.class)  public ResponseBean handleMethodArgumentNotValid(HttpServletRequest request, MethodArgumentNotValidException ex) {    logger.debug(ex);    return validatorErrors(ex.getBindingResult());  }
  private ResponseBean validatorErrors(BindingResult result) {    List<FieldValidatorError> errors = new ArrayList<FieldValidatorError>();    for (FieldError error : result.getFieldErrors()) {      errors.add(toFieldValidatorError(error));    }    return ResponseBean.validatorError(errors);  }
  /**   * ConstraintViolationException: 直接对方法参数进行校验，校验不通过。   * 如: pageUsers(@RequestParam @Min(1)int pageIndex, @RequestParam @Max(100)int pageSize)   */  @ExceptionHandler(ConstraintViolationException.class)  public ResponseBean handleConstraintViolationException(HttpServletRequest request,      ConstraintViolationException ex) {    logger.debug(ex);    //     List<FieldValidatorError> errors = new ArrayList<FieldValidatorError>();
    for (ConstraintViolation<?> violation : ex.getConstraintViolations()) {      errors.add(toFieldValidatorError(violation));    }    return ResponseBean.validatorError(errors);  }
  private FieldValidatorError toFieldValidatorError(ConstraintViolation<?> violation) {    Path.Node lastNode = null;    for (Path.Node node : violation.getPropertyPath()) {      lastNode = node;    }
    FieldValidatorError fieldNotValidError = new FieldValidatorError();    // fieldNotValidError.setType(ValidatorTypeMapping.toType(violation.getConstraintDescriptor().getAnnotation().annotationType()));    fieldNotValidError.setType(ValidatorErrorType.INVALID.value());    fieldNotValidError.setField(lastNode.getName());    fieldNotValidError.setMessage(violation.getMessage());    return fieldNotValidError;  }
  private FieldValidatorError toFieldValidatorError(FieldError error) {    FieldValidatorError fieldNotValidError = new FieldValidatorError();    fieldNotValidError.setType(ValidatorErrorType.INVALID.value());    fieldNotValidError.setField(error.getField());    fieldNotValidError.setMessage(error.getDefaultMessage());    return fieldNotValidError;  }
  /**   * BindException: 数据绑定异常，效果与MethodArgumentNotValidException类似，为MethodArgumentNotValidException的父类   */  @ExceptionHandler(BindException.class)  public ResponseBean handleBindException(HttpServletRequest request, BindException ex) {    logger.debug(ex);    return validatorErrors(ex.getBindingResult());  }
  /**   * 返回值类型转化错误   */  @ExceptionHandler(HttpMessageConversionException.class)  public ResponseBean exceptionHandle(HttpServletRequest request,      HttpMessageConversionException ex) {    return internalServiceError(ex);  }    /**   * 对应 Http 请求头的 accept   * 客户器端希望接受的类型和服务器端返回类型不一致。   * 这里虽然设置了拦截，但是并没有起到作用。需要通过http请求的流程来进一步确定原因。   */  @ExceptionHandler(HttpMediaTypeNotAcceptableException.class)  public ResponseBean handleHttpMediaTypeNotAcceptableException(HttpServletRequest request,      HttpMediaTypeNotAcceptableException ex) {    logger.debug(ex);    StringBuilder messageBuilder = new StringBuilder().append("The media type is not acceptable.")        .append(" Acceptable media types are ");    ex.getSupportedMediaTypes().forEach(t -> messageBuilder.append(t + ", "));    String message = messageBuilder.substring(0, messageBuilder.length() - 2);
    return new ResponseBean(HttpStatus.NOT_ACCEPTABLE.value(), message);  }
  /**   * 对应请求头的 content-type   * 客户端发送的数据类型和服务器端希望接收到的数据不一致   */  @ExceptionHandler(HttpMediaTypeNotSupportedException.class)  public ResponseBean handleHttpMediaTypeNotSupportedException(HttpServletRequest request,      HttpMediaTypeNotSupportedException ex) {     logger.debug(ex);    StringBuilder messageBuilder = new StringBuilder().append(ex.getContentType())        .append(" media type is not supported.").append(" Supported media types are ");    ex.getSupportedMediaTypes().forEach(t -> messageBuilder.append(t + ", "));    String message = messageBuilder.substring(0, messageBuilder.length() - 2);    System.out.println(message);    return new ResponseBean(HttpStatus.UNSUPPORTED_MEDIA_TYPE.value(), message);  }
  /**   * 前端发送过来的数据无法被正常处理   * 比如后天希望收到的是一个json的数据，但是前端发送过来的却是xml格式的数据或者是一个错误的json格式数据   */  @ExceptionHandler(HttpMessageNotReadableException.class)  public ResponseBean handlerHttpMessageNotReadableException(HttpServletRequest request,      HttpMessageNotReadableException ex) {    logger.debug(ex);    String message = "Problems parsing JSON";    return new ResponseBean(HttpStatus.BAD_REQUEST.value(), message);  }
  /**   * 将返回的结果转化到响应的数据时候导致的问题。   * 当使用json作为结果格式时，可能导致的原因为序列化错误。   * 目前知道，如果返回一个没有属性的对象作为结果时，会导致该异常。   */  @ExceptionHandler(HttpMessageNotWritableException.class)  public ResponseBean handlerHttpMessageNotWritableException(HttpServletRequest request,      HttpMessageNotWritableException ex) {    return internalServiceError(ex);  }
  /**   * 请求方法不支持   */  @ExceptionHandler(HttpRequestMethodNotSupportedException.class)  public ResponseBean exceptionHandle(HttpServletRequest request, HttpRequestMethodNotSupportedException ex) {    logger.debug(ex);    StringBuilder messageBuilder = new StringBuilder().append(ex.getMethod())        .append(" method is not supported for this request.").append(" Supported methods are ");
    ex.getSupportedHttpMethods().forEach(m -> messageBuilder.append(m + ","));    String message = messageBuilder.substring(0, messageBuilder.length() - 2);    return new ResponseBean(HttpStatus.METHOD_NOT_ALLOWED.value(), message);  }
  /**   * 参数类型不匹配   */  @ExceptionHandler(MethodArgumentTypeMismatchException.class)  public ResponseBean methodArgumentTypeMismatchExceptionHandler(HttpServletRequest request,      MethodArgumentTypeMismatchException ex) {    logger.debug(ex);    String message = "The parameter '" + ex.getName() + "' should of type '"        + ex.getRequiredType().getSimpleName().toLowerCase() + "'";
    FieldValidatorError fieldNotValidError = new FieldValidatorError();    fieldNotValidError.setType(ValidatorErrorType.TYPE_MISMATCH.value());    fieldNotValidError.setField(ex.getName());    fieldNotValidError.setMessage(message);
    return ResponseBean.validatorError(Arrays.asList(fieldNotValidError));  }
  /**   * 缺少必填字段   */  @ExceptionHandler(MissingServletRequestParameterException.class)  public ResponseBean exceptionHandle(HttpServletRequest request,      MissingServletRequestParameterException ex) {    logger.debug(ex);    String message = "Required parameter '" + ex.getParameterName() + "' is not present";
    FieldValidatorError fieldNotValidError = new FieldValidatorError();    fieldNotValidError.setType(ValidatorErrorType.MISSING_FIELD.value());    fieldNotValidError.setField(ex.getParameterName());    fieldNotValidError.setMessage(message);
    return ResponseBean.validatorError(Arrays.asList(fieldNotValidError));  }
  /**   * 文件上传时，缺少　file 字段   */  @ExceptionHandler(MissingServletRequestPartException.class)  public ResponseBean exceptionHandle(HttpServletRequest request, MissingServletRequestPartException ex) {    logger.debug(ex);    return new ResponseBean(HttpStatus.BAD_REQUEST.value(), ex.getMessage());  }
  /**   * 请求路径不存在   */  @ExceptionHandler(NoHandlerFoundException.class)  public ResponseBean exceptionHandle(HttpServletRequest request, NoHandlerFoundException ex) {    logger.debug(ex);    String message = "No resource found for " + ex.getHttpMethod() + " " + ex.getRequestURL();    return new ResponseBean(HttpStatus.NOT_FOUND.value(), message);  }
  /**   * 缺少路径参数   * Controller方法中定义了　@PathVariable(required=true)　的参数，但是却没有在url中提供   */  @ExceptionHandler(MissingPathVariableException.class)  public ResponseBean exceptionHandle(HttpServletRequest request, MissingPathVariableException ex) {    return internalServiceError(ex);  }
  /**   * 其他所有的异常   */  @ExceptionHandler()  public ResponseBean handleAll(HttpServletRequest request, Exception ex) {    return internalServiceError(ex);  }
  private String codeToMessage(int code) {    //TODO 这个需要进行自定，每个 code 会匹配到一个相应的 msg    return "The code is " + code;  }
  private ResponseBean internalServiceError(Exception ex) {    logException(ex);    // do something else    return ResponseBean.systemError();  }
  private <T extends Throwable> void logException(T e) {    logger.error(String.format(logExceptionFormat, e.getMessage()), e);  }}

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通过上面的配置，可以有效地将异常进行统一的处理，同时对返回的结果进行统一的封装。

发布于: 3 小时前阅读数: 2

原文链接:【http://xie.infoq.cn/article/a723a9a7610d54eac8dda0c25】。文章转载请联系作者。

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SpringMVC | Controller 返回值及异常的统一处理

旧的设计方案

统一 Controller 返回值格式

统一异常处理

DoneSpeak

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