如何在返回字符串的 Spring MVC @ResponseBody方法中响应 HTTP 400 错误

这不一定是最紧凑的方式，但在我看来相当干净：

if(json == null) {
    throw new BadThingException();
}
...

@ExceptionHandler(BadThingException.class)
@ResponseStatus(value = HttpStatus.BAD_REQUEST)
public @ResponseBody MyError handleException(BadThingException e) {
    return new MyError("That doesn’t work");
}

如果使用 Spring 3.1+，则可以在异常处理程序方法中使用 @ResponseBody，否则使用 a 或其他东西。ModelAndView

@ResponseBody不适用于@ExceptionHandler [SPR-6902] #11567

这样的东西应该有效，但我不确定是否有更简单的方法：

@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public String match(@PathVariable String matchId, @RequestBody String body,
            HttpServletRequest request, HttpServletResponse response) {
    String json = matchService.getMatchJson(matchId);
    if (json == null) {
        response.setStatus( HttpServletResponse.SC_BAD_REQUEST  );
    }
    return json;
}

将返回类型更改为 ，然后您可以将以下内容用于 400：ResponseEntity<>

return new ResponseEntity<>(HttpStatus.BAD_REQUEST);

对于正确的请求：

return new ResponseEntity<>(json,HttpStatus.OK);

在 Spring 4.1 之后，ResponseEntity 中有一些辅助方法，可以用作：

return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(null);

和

return ResponseEntity.ok(json);

我会稍微改变实现：

首先，我创建一个：UnknownMatchException

@ResponseStatus(HttpStatus.NOT_FOUND)
public class UnknownMatchException extends RuntimeException {
    public UnknownMatchException(String matchId) {
        super("Unknown match: " + matchId);
    }
}

请注意 @ResponseStatus 的使用，Spring 的 .如果抛出异常，它将创建具有相应响应状态的响应。（我还冒昧地更改了我认为更适合此用例的状态代码，但如果您愿意，您可以坚持使用。ResponseStatusExceptionResolver404 - Not FoundHttpStatus.BAD_REQUEST

---

接下来，我将更改为具有以下签名：MatchService

interface MatchService {
    public Match findMatch(String matchId);
}

---

最后，我会更新控制器并委托给 Spring 以自动处理 JSON 序列化（如果您将 Jackson 添加到类路径并添加其中任何一个或您的配置，则默认情况下会添加它。请参阅参考文档）：MappingJackson2HttpMessageConverter@EnableWebMvc<mvc:annotation-driven />

@RequestMapping(value = "/matches/{matchId}", produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public Match match(@PathVariable String matchId) {
    // Throws an UnknownMatchException if the matchId is not known
    return matchService.findMatch(matchId);
}

---

请注意，将域对象与视图对象或 DTO 对象分开是很常见的。这可以通过添加一个返回可序列化的 JSON 对象的小型 DTO 工厂来轻松实现：

@RequestMapping(value = "/matches/{matchId}", produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public MatchDTO match(@PathVariable String matchId) {
    Match match = matchService.findMatch(matchId);
    return MatchDtoFactory.createDTO(match);
}

我正在我的Spring Boot应用程序中使用它：

@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public ResponseEntity<?> match(@PathVariable String matchId, @RequestBody String body,
            HttpServletRequest request, HttpServletResponse response) {

    Product p;
    try {
      p = service.getProduct(request.getProductId());
    } catch(Exception ex) {
       return new ResponseEntity<String>(HttpStatus.BAD_REQUEST);
    }

    return new ResponseEntity(p, HttpStatus.OK);
}

这是一种不同的方法。创建一个带有 注释的自定义，如下所示。Exception@ResponseStatus

@ResponseStatus(code = HttpStatus.NOT_FOUND, reason = "Not Found")
public class NotFoundException extends Exception {

    public NotFoundException() {
    }
}

并在需要时扔掉它。

@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public String match(@PathVariable String matchId) {
    String json = matchService.getMatchJson(matchId);
    if (json == null) {
        throw new NotFoundException();
    }
    return json;
}

正如某些答案中提到的，可以为要返回的每个 HTTP 状态创建一个异常类。我不喜欢必须为每个项目创建每个状态的类的想法。这是我想出的。

• 创建接受 HTTP 状态的泛型异常
• 创建 Controller Advice 异常处理程序

让我们来看看代码

package com.javaninja.cam.exception;

import org.springframework.http.HttpStatus;


/**
 * The exception used to return a status and a message to the calling system.
 * @author norrisshelton
 */
@SuppressWarnings("ClassWithoutNoArgConstructor")
public class ResourceException extends RuntimeException {

    private HttpStatus httpStatus = HttpStatus.INTERNAL_SERVER_ERROR;

    /**
     * Gets the HTTP status code to be returned to the calling system.
     * @return http status code.  Defaults to HttpStatus.INTERNAL_SERVER_ERROR (500).
     * @see HttpStatus
     */
    public HttpStatus getHttpStatus() {
        return httpStatus;
    }

    /**
     * Constructs a new runtime exception with the specified HttpStatus code and detail message.
     * The cause is not initialized, and may subsequently be initialized by a call to {@link #initCause}.
     * @param httpStatus the http status.  The detail message is saved for later retrieval by the {@link
     *                   #getHttpStatus()} method.
     * @param message    the detail message. The detail message is saved for later retrieval by the {@link
     *                   #getMessage()} method.
     * @see HttpStatus
     */
    public ResourceException(HttpStatus httpStatus, String message) {
        super(message);
        this.httpStatus = httpStatus;
    }
}

然后我创建一个控制器建议类

package com.javaninja.cam.spring;


import com.javaninja.cam.exception.ResourceException;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ExceptionHandler;


/**
 * Exception handler advice class for all SpringMVC controllers.
 * @author norrisshelton
 * @see org.springframework.web.bind.annotation.ControllerAdvice
 */
@org.springframework.web.bind.annotation.ControllerAdvice
public class ControllerAdvice {

    /**
     * Handles ResourceExceptions for the SpringMVC controllers.
     * @param e SpringMVC controller exception.
     * @return http response entity
     * @see ExceptionHandler
     */
    @ExceptionHandler(ResourceException.class)
    public ResponseEntity handleException(ResourceException e) {
        return ResponseEntity.status(e.getHttpStatus()).body(e.getMessage());
    }
}

使用它

throw new ResourceException(HttpStatus.BAD_REQUEST, "My message");

http://javaninja.net/2016/06/throwing-exceptions-messages-spring-mvc-controller/

对于Spring Boot，我不完全确定为什么这是必要的（即使我得到了回退，即使定义在 ），但以下内容本身不起作用：/error@ResponseBody@ExceptionHandler

@ResponseBody
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(IllegalArgumentException.class)
public ErrorMessage handleIllegalArguments(HttpServletRequest httpServletRequest, IllegalArgumentException e) {
    log.error("Illegal arguments received.", e);
    ErrorMessage errorMessage = new ErrorMessage();
    errorMessage.code = 400;
    errorMessage.message = e.getMessage();
    return errorMessage;
}

它仍然抛出一个异常，显然是因为没有可生产的媒体类型被定义为请求属性：

// AbstractMessageConverterMethodProcessor
@SuppressWarnings("unchecked")
protected <T> void writeWithMessageConverters(T value, MethodParameter returnType,
        ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage)
        throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {

    Class<?> valueType = getReturnValueType(value, returnType);
    Type declaredType = getGenericType(returnType);
    HttpServletRequest request = inputMessage.getServletRequest();
    List<MediaType> requestedMediaTypes = getAcceptableMediaTypes(request);
    List<MediaType> producibleMediaTypes = getProducibleMediaTypes(request, valueType, declaredType);
if (value != null && producibleMediaTypes.isEmpty()) {
        throw new IllegalArgumentException("No converter found for return value of type: " + valueType);   // <-- throws
    }

// ....

@SuppressWarnings("unchecked")
protected List<MediaType> getProducibleMediaTypes(HttpServletRequest request, Class<?> valueClass, Type declaredType) {
    Set<MediaType> mediaTypes = (Set<MediaType>) request.getAttribute(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE);
    if (!CollectionUtils.isEmpty(mediaTypes)) {
        return new ArrayList<MediaType>(mediaTypes);

所以我添加了它们。

@ResponseBody
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(IllegalArgumentException.class)
public ErrorMessage handleIllegalArguments(HttpServletRequest httpServletRequest, IllegalArgumentException e) {
    Set<MediaType> mediaTypes = new HashSet<>();
    mediaTypes.add(MediaType.APPLICATION_JSON_UTF8);
    httpServletRequest.setAttribute(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE, mediaTypes);
    log.error("Illegal arguments received.", e);
    ErrorMessage errorMessage = new ErrorMessage();
    errorMessage.code = 400;
    errorMessage.message = e.getMessage();
    return errorMessage;
}

这让我获得了“支持的兼容媒体类型”，但后来它仍然不起作用，因为我有问题：ErrorMessage

public class ErrorMessage {
    int code;

    String message;
}

JacksonMapper 没有将其处理为“可转换”，所以我不得不添加 getters/setter，并且我还添加了注释@JsonProperty

public class ErrorMessage {
    @JsonProperty("code")
    private int code;

    @JsonProperty("message")
    private String message;

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

然后我按预期收到了我的消息

{"code":400,"message":"An \"url\" parameter must be defined."}

你也可以抛出新的 HttpMessageNotReadableException（“error description”） 来从 Spring 的默认错误处理中受益。

但是，与这些默认错误一样，不会设置响应正文。

我发现这些在拒绝只能合理地手工制作的请求时很有用，这可能表明恶意意图，因为它们掩盖了基于更深入的自定义验证及其标准拒绝请求的事实。

最简单的方法是抛出一个：ResponseStatusException

@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public String match(@PathVariable String matchId, @RequestBody String body) {
    String json = matchService.getMatchJson(matchId);
    if (json == null) {
        throw new ResponseStatusException(HttpStatus.NOT_FOUND);
    }
    return json;
}

另一种方法是使用 with 将所有处理程序集中到同一个类中。否则，必须将处理程序方法放在要为其管理异常的每个控制器中。@ExceptionHandler@ControllerAdvice

处理程序类：

@ControllerAdvice
public class MyExceptionHandler extends ResponseEntityExceptionHandler {

  @ExceptionHandler(MyBadRequestException.class)
  public ResponseEntity<MyError> handleException(MyBadRequestException e) {
    return ResponseEntity
        .badRequest()
        .body(new MyError(HttpStatus.BAD_REQUEST, e.getDescription()));
  }
}

您的自定义例外：

public class MyBadRequestException extends RuntimeException {

  private String description;

  public MyBadRequestException(String description) {
    this.description = description;
  }

  public String getDescription() {
    return this.description;
  }
}

现在，您可以从任何控制器引发异常，并且可以在建议类中定义其他处理程序。

使用带有状态代码的自定义响应。

喜欢这个：

class Response<T>(
    val timestamp: String = DateTimeFormatter
            .ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSS")
            .withZone(ZoneOffset.UTC)
            .format(Instant.now()),
    val code: Int = ResultCode.SUCCESS.code,
    val message: String? = ResultCode.SUCCESS.message,
    val status: HttpStatus = HttpStatus.OK,
    val error: String? = "",
    val token: String? = null,
    val data: T? = null
) : : ResponseEntity<Response.CustomResponseBody>(status) {

data class CustomResponseBody(
    val timestamp: String = DateTimeFormatter
            .ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSS")
            .withZone(ZoneOffset.UTC)
            .format(Instant.now()),
    val code: Int = ResultCode.SUCCESS.code,
    val message: String? = ResultCode.SUCCESS.message,
    val error: String? = "",
    val token: String? = null,
    val data: Any? = null
)

override fun getBody(): CustomResponseBody? = CustomResponseBody(timestamp, code, message, error, token, data)

在控制器中处理异常而不必显式返回的最简单、最干净的方法是添加方法。ResponseEntity@ExceptionHandler

使用 Spring Boot 2.0.3.RELEASE 的示例代码片段：

// Prefer static import of HttpStatus constants as it's cleaner IMHO

// Handle with no content returned
@ExceptionHandler(IllegalArgumentException.class)
@ResponseStatus(BAD_REQUEST)
void onIllegalArgumentException() {}

// Return 404 when JdbcTemplate does not return a single row
@ExceptionHandler(IncorrectResultSizeDataAccessException.class)
@ResponseStatus(NOT_FOUND)
void onIncorrectResultSizeDataAccessException() {}

// Catch all handler with the exception as content
@ExceptionHandler(Exception.class)
@ResponseStatus(I_AM_A_TEAPOT)
@ResponseBody Exception onException(Exception e) {
  return e;
}

顺便说一句：

• 如果在所有上下文/用法中都是无效的，那么我的建议是抛出一个异常，例如，而不是返回并让它冒泡到控制器的 .matchService.getMatchJson(matchId) == nullgetMatchJsonIllegalArgumentExceptionnull@ExceptionHandler

• 如果用于测试其他条件，那么我将有一个特定的方法，例如， .一般来说，如果可能的话，我会避免，以避免意外。nullmatchService.hasMatchJson(matchId)nullNullPointerException