json - @ControllerAdvice 无法返回 ResponseEntity(T 是 POJO)

Question

我正在使用 Spring 4 MVC 创建 REST API。
我希望我可以在请求无效端点时提供默认的 JSON 错误对象。
我已经阅读了关于 @ControllerAdvice 和 @ExceptionHandler 的信息，我试图正确使用它们:

package com.yopyop.wackend.controller;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.NoHandlerFoundException;

import com.yopyop.wackend.controller.ErrorResponse;
import com.yopyop.wackend.service.NotFoundException;


@ControllerAdvice
public class ExceptionControllerAdvice {

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ErrorResponse> exceptionHandler(Exception ex) {

        ErrorResponse error = new ErrorResponse();
        error.setErrorCode(HttpStatus.INTERNAL_SERVER_ERROR.value());

        if (ex.getClass()==NotFoundException.class) {
            error.setMessage("ExceptionControllerAdvice() Not found");
            error.setErrorCode(HttpStatus.NOT_FOUND.value());
            return new ResponseEntity<ErrorResponse>(error, HttpStatus.NOT_FOUND);
        }
        else {
            error.setMessage("ExceptionControllerAdvice() " + ex.getClass() + "(" + ex.getMessage() + ")");
            error.setErrorCode(HttpStatus.INTERNAL_SERVER_ERROR.value());
        }

        return new ResponseEntity<ErrorResponse>(error, HttpStatus.INTERNAL_SERVER_ERROR);
    }

    @ExceptionHandler({NoHandlerFoundException.class})
    ResponseEntity<ErrorResponse> handleNoHandlerFoundException(NoHandlerFoundException ex,
            WebRequest request) {

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);

        ErrorResponse error = new ErrorResponse();
        error.setErrorCode(HttpStatus.INTERNAL_SERVER_ERROR.value());
        error.setMessage("ExceptionControllerAdvice() " + ex.getClass() + "(" + ex.getMessage() + ")");

        return new ResponseEntity<ErrorResponse>(error, HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

我的 ErrorResponse 类如下:

package com.yopyop.wackend.controller;

public class ErrorResponse {
    private int errorCode;
    private String message;

    public int getErrorCode() {
        return errorCode;
    }
    public void setErrorCode(int errorCode) {
        this.errorCode = errorCode;
    }
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
}

我修改了 web.xml 以便抛出 NoHandlerFound 异常:

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Wackend WebApp</display-name>
  <servlet>
 <servlet-name>wackend</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>

 <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
 <servlet-name>wackend</servlet-name>
 <url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>

尽管如此，当收到对未映射端点的请求时，我得到:

> 22:47:28.545 [http-nio-8080-exec-15] DEBUG
> o.s.web.servlet.DispatcherServlet - DispatcherServlet with name
> 'wackend' processing GET request for [/wackend/swagger-ui.html]
> 22:47:28.548 [http-nio-8080-exec-15] DEBUG
> o.s.w.s.m.m.a.RequestMappingHandlerMapping - Looking up handler method
> for path /swagger-ui.html 22:47:28.552 [http-nio-8080-exec-15] DEBUG
> o.s.w.s.m.m.a.RequestMappingHandlerMapping - Returning handler method
> [public void
> com.yopyop.wackend.controller.DefaultController.unmappedRequest(javax.servlet.http.HttpServletRequest)
> throws org.springframework.web.servlet.NoHandlerFoundException]
> 22:47:28.552 [http-nio-8080-exec-15] DEBUG
> o.s.b.f.s.DefaultListableBeanFactory - Returning cached instance of
> singleton bean 'defaultController' 22:47:28.553
> [http-nio-8080-exec-15] DEBUG o.s.web.servlet.DispatcherServlet -
> Last-Modified value for [/wackend/swagger-ui.html] is: -1 22:47:28.566
> [http-nio-8080-exec-15] DEBUG
> o.s.w.s.m.m.a.ExceptionHandlerExceptionResolver - Resolving exception
> from handler [public void
> com.yopyop.wackend.controller.DefaultController.unmappedRequest(javax.servlet.http.HttpServletRequest)
> throws org.springframework.web.servlet.NoHandlerFoundException]:
> org.springframework.web.servlet.NoHandlerFoundException: No handler
> found for GET /wackend/swagger-ui.html, headers={} 22:47:28.567
> [http-nio-8080-exec-15] DEBUG o.s.b.f.s.DefaultListableBeanFactory -
> Returning cached instance of singleton bean
> 'exceptionControllerAdvice' 22:47:28.567 [http-nio-8080-exec-15] DEBUG
> o.s.w.s.m.m.a.ExceptionHandlerExceptionResolver - Invoking
> @ExceptionHandler method:
> org.springframework.http.ResponseEntity<com.yopyop.wackend.controller.ErrorResponse>
> com.yopyop.wackend.controller.ExceptionControllerAdvice.handleNoHandlerFoundException(org.springframework.web.servlet.NoHandlerFoundException,org.springframework.web.context.request.WebRequest)
> 22:47:28.603 [http-nio-8080-exec-15] ERROR
> o.s.w.s.m.m.a.ExceptionHandlerExceptionResolver - Failed to invoke
> @ExceptionHandler method:
> org.springframework.http.ResponseEntity<com.yopyop.wackend.controller.ErrorResponse>
> com.yopyop.wackend.controller.ExceptionControllerAdvice.handleNoHandlerFoundException(org.springframework.web.servlet.NoHandlerFoundException,org.springframework.web.context.request.WebRequest)
> org.springframework.web.HttpMediaTypeNotAcceptableException: Could not
> find acceptable representation    at
> org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:134)
> ~[spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]  at
> org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:146)
> ~[spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]  at
> org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71)
> ~[spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE] [...]   at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> [na:1.8.0_101]    at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> [na:1.8.0_101]    at
> org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
> [tomcat-util.jar:8.0.36]  at java.lang.Thread.run(Thread.java:745)
> [na:1.8.0_101] 22:47:28.603 [http-nio-8080-exec-15] DEBUG
> o.s.w.s.m.m.a.ExceptionHandlerExceptionResolver - Resolving exception
> from handler [public void
> com.yopyop.wackend.controller.DefaultController.unmappedRequest(javax.servlet.http.HttpServletRequest)
> throws org.springframework.web.servlet.NoHandlerFoundException]:
> org.springframework.web.servlet.NoHandlerFoundException: No handler
> found for GET /wackend/swagger-ui.html, headers={} 22:47:28.603
> [http-nio-8080-exec-15] DEBUG o.s.b.f.s.DefaultListableBeanFactory -
> Returning cached instance of singleton bean
> 'exceptionControllerAdvice' 22:47:28.603 [http-nio-8080-exec-15] DEBUG
> o.s.w.s.m.m.a.ExceptionHandlerExceptionResolver - Invoking
> @ExceptionHandler method:
> org.springframework.http.ResponseEntity<com.yopyop.wackend.controller.ErrorResponse>
> com.yopyop.wackend.controller.ExceptionControllerAdvice.handleNoHandlerFoundException(org.springframework.web.servlet.NoHandlerFoundException,org.springframework.web.context.request.WebRequest)
> 22:47:28.604 [http-nio-8080-exec-15] ERROR
> o.s.w.s.m.m.a.ExceptionHandlerExceptionResolver - Failed to invoke
> @ExceptionHandler method:
> org.springframework.http.ResponseEntity<com.yopyop.wackend.controller.ErrorResponse>
> com.yopyop.wackend.controller.ExceptionControllerAdvice.handleNoHandlerFoundException(org.springframework.web.servlet.NoHandlerFoundException,org.springframework.web.context.request.WebRequest)
> org.springframework.web.HttpMediaTypeNotAcceptableException: Could not
> find acceptable representation    at
> org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:134)
> ~[spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]  at
> org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:146)
> ~[spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE]  at
> org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71)
> ~[spring-web-4.1.6.RELEASE.jar:4.1.6.RELEASE]     at
> org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126)
> ~[spring-webmvc-4.1.6.RELEASE.jar:4.1.6.RELEASE] [...]    at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> [na:1.8.0_101]    at
> org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
> [tomcat-util.jar:8.0.36]  at java.lang.Thread.run(Thread.java:745)
> [na:1.8.0_101] 22:47:28.604 [http-nio-8080-exec-15] DEBUG
> o.s.w.s.m.a.ResponseStatusExceptionResolver - Resolving exception from
> handler [public void
> com.yopyop.wackend.controller.DefaultController.unmappedRequest(javax.servlet.http.HttpServletRequest)
> throws org.springframework.web.servlet.NoHandlerFoundException]:
> org.springframework.web.servlet.NoHandlerFoundException: No handler
> found for GET /wackend/swagger-ui.html, headers={} 22:47:28.604
> [http-nio-8080-exec-15] DEBUG
> o.s.w.s.m.s.DefaultHandlerExceptionResolver - Resolving exception from
> handler [public void
> com.yopyop.wackend.controller.DefaultController.unmappedRequest(javax.servlet.http.HttpServletRequest)
> throws org.springframework.web.servlet.NoHandlerFoundException]:
> org.springframework.web.servlet.NoHandlerFoundException: No handler
> found for GET /wackend/swagger-ui.html, headers={} 22:47:28.604
> [http-nio-8080-exec-15] DEBUG o.s.web.servlet.DispatcherServlet - Null
> ModelAndView returned to DispatcherServlet with name 'wackend':
> assuming HandlerAdapter completed request handling 22:47:28.604
> [http-nio-8080-exec-15] DEBUG o.s.web.servlet.DispatcherServlet -
> Successfully completed request

然后返回一个标准的Tomcat 404页面。
请不要那样:

返回新的响应实体(错误，
HttpStatus.INTERNAL_SERVER_ERROR);

将返回一个带有空体的 HTTP 500(比 Tomcat 更好
默认页面)

返回新的响应实体(“woot”，
HttpStatus.INTERNAL_SERVER_ERROR);将返回一个带有 woot 作为主体的 HTTP 500。

看起来我的 ErrorResponse 类无法完成 JSON 映射。

此外，我使用默认 Controller ，但我想它没用，因为我使用了@ControllerAdvice。我把它贴在这里以获取信息:

package com.yopyop.wackend.controller;

import javax.servlet.http.HttpServletRequest;

import org.springframework.http.HttpHeaders;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.NoHandlerFoundException;

/**
 * Default controller that exists to return a proper REST response for unmapped requests.
 */
@Controller
public class DefaultController {

    @RequestMapping("/**")
    public void unmappedRequest(HttpServletRequest request) throws NoHandlerFoundException {
        String uri = request.getRequestURI();
        String method = request.getMethod();
        HttpHeaders h = new HttpHeaders();

        throw new NoHandlerFoundException(method, uri, h);
    }
}

我的 REST API 也使用 ResponseEntity<> 返回并成功返回正确的 JSON 有效负载。

Answer 1

我不知道确切的答案是什么，但问题可能出在 JSON 配置上。起初，您的 @Controller 不是 @RestController 并且您没有明确指定生成的内容。我希望你在你的请求中这样做，所以 spring 知道该怎么做。我认为来自@Controller 的 mime 类型是继承的并用于转换。

您可以尝试在 http 消息转换器中添加断点。在每个转换器中都有一个数学方法 supports尝试在此处捕获您的代码。检查哪个转换器返回 true。如果有多个通过条件，Spring 将使用第一个。通过堆栈跟踪，您还可以找到哪些转换器可用于您的请求以及需要哪种转换器。

http://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/http/converter/AbstractHttpMessageConverter.html#supports-java.lang.Class-