Spring REST API 的自定义错误消息处理

最后修改:2024年5月11日

by baeldung

1. 概述

本教程将讨论如何为 Spring REST API 实现一个全局异常处理器。

我们的目标是根据每个异常的语义，构建出对客户端有意义的错误信息，让客户端能够轻松诊断问题。

2. 自定义错误消息结构

我们先来实现一个简单的错误信息传输结构 —— ApiError：

public class ApiError {

    private HttpStatus status;
    private String message;
    private List<String> errors;

    public ApiError(HttpStatus status, String message, List<String> errors) {
        super();
        this.status = status;
        this.message = message;
        this.errors = errors;
    }

    public ApiError(HttpStatus status, String message, String error) {
        super();
        this.status = status;
        this.message = message;
        errors = Arrays.asList(error);
    }
}

字段含义如下：

  • status – HTTP 状态码
  • message – 与异常相关的错误信息
  • errors – 构造的错误消息列表

在 Spring 中处理异常时，我们将使用 @ControllerAdvice 注解：

@ControllerAdvice
public class CustomRestExceptionHandler extends ResponseEntityExceptionHandler {
    ...
}

3. 处理 Bad Request 异常

3.1. 异常处理逻辑

我们先来看最常见的客户端错误处理场景 —— 客户端发送了无效请求：

✅ BindException 和 MethodArgumentNotValidException

当方法参数使用 @Valid 注解校验失败时会抛出 MethodArgumentNotValidException：

@Override
protected ResponseEntity<Object> handleMethodArgumentNotValid(
  MethodArgumentNotValidException ex, 
  HttpHeaders headers, 
  HttpStatus status, 
  WebRequest request) {
    List<String> errors = new ArrayList<String>();
    for (FieldError error : ex.getBindingResult().getFieldErrors()) {
        errors.add(error.getField() + ": " + error.getDefaultMessage());
    }
    for (ObjectError error : ex.getBindingResult().getGlobalErrors()) {
        errors.add(error.getObjectName() + ": " + error.getDefaultMessage());
    }
    
    ApiError apiError = 
      new ApiError(HttpStatus.BAD_REQUEST, ex.getLocalizedMessage(), errors);
    return handleExceptionInternal(
      ex, apiError, headers, apiError.getStatus(), request);
}

⚠️ 注意：我们是在重写 ResponseEntityExceptionHandler 中的方法，实现自己的处理逻辑。

✅ MissingServletRequestPartException 和 MissingServletRequestParameterException

分别用于处理 multipart 请求缺失部分和请求参数缺失的情况：

@Override
protected ResponseEntity<Object> handleMissingServletRequestParameter(
  MissingServletRequestParameterException ex, HttpHeaders headers, 
  HttpStatus status, WebRequest request) {
    String error = ex.getParameterName() + " parameter is missing";
    
    ApiError apiError = 
      new ApiError(HttpStatus.BAD_REQUEST, ex.getLocalizedMessage(), error);
    return new ResponseEntity<Object>(
      apiError, new HttpHeaders(), apiError.getStatus());
}

✅ ConstraintViolationException

用于处理 Bean Validation 中的约束违反：

@ExceptionHandler({ ConstraintViolationException.class })
public ResponseEntity<Object> handleConstraintViolation(
  ConstraintViolationException ex, WebRequest request) {
    List<String> errors = new ArrayList<String>();
    for (ConstraintViolation<?> violation : ex.getConstraintViolations()) {
        errors.add(violation.getRootBeanClass().getName() + " " + 
          violation.getPropertyPath() + ": " + violation.getMessage());
    }

    ApiError apiError = 
      new ApiError(HttpStatus.BAD_REQUEST, ex.getLocalizedMessage(), errors);
    return new ResponseEntity<Object>(
      apiError, new HttpHeaders(), apiError.getStatus());
}

✅ MethodArgumentTypeMismatchException

用于处理参数类型不匹配的情况：

@ExceptionHandler({ MethodArgumentTypeMismatchException.class })
public ResponseEntity<Object> handleMethodArgumentTypeMismatch(
  MethodArgumentTypeMismatchException ex, WebRequest request) {
    String error = 
      ex.getName() + " should be of type " + ex.getRequiredType().getName();

    ApiError apiError = 
      new ApiError(HttpStatus.BAD_REQUEST, ex.getLocalizedMessage(), error);
    return new ResponseEntity<Object>(
      apiError, new HttpHeaders(), apiError.getStatus());
}

3.2. 客户端调用示例

我们来看一个测试，模拟 MethodArgumentTypeMismatchException：

@Test
public void whenMethodArgumentMismatch_thenBadRequest() {
    Response response = givenAuth().get(URL_PREFIX + "/api/foos/ccc");
    ApiError error = response.as(ApiError.class);

    assertEquals(HttpStatus.BAD_REQUEST, error.getStatus());
    assertEquals(1, error.getErrors().size());
    assertTrue(error.getErrors().get(0).contains("should be of type"));
}

发送的请求如下：

Request method:    GET
Request path:    http://localhost:8080/spring-security-rest/api/foos/ccc

返回的 JSON 错误信息如下：

{
    "status": "BAD_REQUEST",
    "message": 
      "Failed to convert value of type [java.lang.String] 
       to required type [java.lang.Long]; nested exception 
       is java.lang.NumberFormatException: For input string: \"ccc\"",
    "errors": [
        "id should be of type java.lang.Long"
    ]
}

4. 处理 NoHandlerFoundException

我们可以配置 Servlet，使其在找不到处理方法时抛出异常而不是返回 404：

<servlet>
    <servlet-name>api</servlet-name>
    <servlet-class>
      org.springframework.web.servlet.DispatcherServlet</servlet-class>        
    <init-param>
        <param-name>throwExceptionIfNoHandlerFound</param-name>
        <param-value>true</param-value>
    </init-param>
</servlet>

然后就可以像其他异常一样处理：

@Override
protected ResponseEntity<Object> handleNoHandlerFoundException(
  NoHandlerFoundException ex, HttpHeaders headers, HttpStatus status, WebRequest request) {
    String error = "No handler found for " + ex.getHttpMethod() + " " + ex.getRequestURL();

    ApiError apiError = new ApiError(HttpStatus.NOT_FOUND, ex.getLocalizedMessage(), error);
    return new ResponseEntity<Object>(apiError, new HttpHeaders(), apiError.getStatus());
}

测试代码：

@Test
public void whenNoHandlerForHttpRequest_thenNotFound() {
    Response response = givenAuth().delete(URL_PREFIX + "/api/xx");
    ApiError error = response.as(ApiError.class);

    assertEquals(HttpStatus.NOT_FOUND, error.getStatus());
    assertEquals(1, error.getErrors().size());
    assertTrue(error.getErrors().get(0).contains("No handler found"));
}

请求如下：

Request method:    DELETE
Request path:    http://localhost:8080/spring-security-rest/api/xx

错误响应如下：

{
    "status":"NOT_FOUND",
    "message":"No handler found for DELETE /spring-security-rest/api/xx",
    "errors":[
        "No handler found for DELETE /spring-security-rest/api/xx"
    ]
}

5. 处理 HttpRequestMethodNotSupportedException

当客户端使用了不支持的 HTTP 方法时会抛出该异常：

@Override
protected ResponseEntity<Object> handleHttpRequestMethodNotSupported(
  HttpRequestMethodNotSupportedException ex, 
  HttpHeaders headers, 
  HttpStatus status, 
  WebRequest request) {
    StringBuilder builder = new StringBuilder();
    builder.append(ex.getMethod());
    builder.append(
      " method is not supported for this request. Supported methods are ");
    ex.getSupportedHttpMethods().forEach(t -> builder.append(t + " "));

    ApiError apiError = new ApiError(HttpStatus.METHOD_NOT_ALLOWED, 
      ex.getLocalizedMessage(), builder.toString());
    return new ResponseEntity<Object>(
      apiError, new HttpHeaders(), apiError.getStatus());
}

测试代码：

@Test
public void whenHttpRequestMethodNotSupported_thenMethodNotAllowed() {
    Response response = givenAuth().delete(URL_PREFIX + "/api/foos/1");
    ApiError error = response.as(ApiError.class);

    assertEquals(HttpStatus.METHOD_NOT_ALLOWED, error.getStatus());
    assertEquals(1, error.getErrors().size());
    assertTrue(error.getErrors().get(0).contains("Supported methods are"));
}

请求如下：

Request method:    DELETE
Request path:    http://localhost:8080/spring-security-rest/api/foos/1

错误响应如下：

{
    "status":"METHOD_NOT_ALLOWED",
    "message":"Request method 'DELETE' not supported",
    "errors":[
        "DELETE method is not supported for this request. Supported methods are GET "
    ]
}

6. 处理 HttpMediaTypeNotSupportedException

当客户端发送了不支持的媒体类型时抛出该异常：

@Override
protected ResponseEntity<Object> handleHttpMediaTypeNotSupported(
  HttpMediaTypeNotSupportedException ex, 
  HttpHeaders headers, 
  HttpStatus status, 
  WebRequest request) {
    StringBuilder builder = new StringBuilder();
    builder.append(ex.getContentType());
    builder.append(" media type is not supported. Supported media types are ");
    ex.getSupportedMediaTypes().forEach(t -> builder.append(t + ", "));

    ApiError apiError = new ApiError(HttpStatus.UNSUPPORTED_MEDIA_TYPE, 
      ex.getLocalizedMessage(), builder.substring(0, builder.length() - 2));
    return new ResponseEntity<Object>(
      apiError, new HttpHeaders(), apiError.getStatus());
}

测试代码：

@Test
public void whenSendInvalidHttpMediaType_thenUnsupportedMediaType() {
    Response response = givenAuth().body("").post(URL_PREFIX + "/api/foos");
    ApiError error = response.as(ApiError.class);

    assertEquals(HttpStatus.UNSUPPORTED_MEDIA_TYPE, error.getStatus());
    assertEquals(1, error.getErrors().size());
    assertTrue(error.getErrors().get(0).contains("media type is not supported"));
}

请求如下：

Request method:    POST
Request path:    http://localhost:8080/spring-security-
Headers:    Content-Type=text/plain; charset=ISO-8859-1

错误响应如下：

{
    "status":"UNSUPPORTED_MEDIA_TYPE",
    "message":"Content type 'text/plain;charset=ISO-8859-1' not supported",
    "errors":["text/plain;charset=ISO-8859-1 media type is not supported. 
       Supported media types are text/xml 
       application/x-www-form-urlencoded 
       application/*+xml 
       application/json;charset=UTF-8 
       application/*+json;charset=UTF-8 */"
    ]
}

7. 默认异常处理器

最后，我们实现一个兜底的异常处理器，用于处理未被其他方法覆盖的异常：

@ExceptionHandler({ Exception.class })
public ResponseEntity<Object> handleAll(Exception ex, WebRequest request) {
    ApiError apiError = new ApiError(
      HttpStatus.INTERNAL_SERVER_ERROR, ex.getLocalizedMessage(), "error occurred");
    return new ResponseEntity<Object>(
      apiError, new HttpHeaders(), apiError.getStatus());
}

8. 总结

构建一个成熟、完善的 Spring REST API 异常处理器并非一蹴而就，需要在实践中不断迭代。希望本教程能为你提供一个良好的起点，帮助客户端快速定位和解决问题。

完整的代码示例可以在这里找到：GitHub 项目地址。这是一个基于 Eclipse 的项目，可直接导入运行。

原始标题:Custom Error Message Handling for REST API

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