@ControllerAdvice返回ResponseEntity失败（T是POJO）

Question

我正在使用Spring4 MVC创建一个REST API。我希望能够在请求无效endpoint时提供一个默认的JSON错误对象。我读过关于@ControllerAdvice和@ExceptionHandler的文章，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类如下所示：

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>

> 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

然后返回标准Tomcat404页。请不要说：

>

返回新的ResponseEntity（错误，HttpStatus.internal_server_error)；

将返回一个带有空正文的HTTP500（比Tomcat默认页面更好）

另外，我使用了一个默认控制器，但我猜它没有用，因为我使用了@ControllerAdvice。我粘贴在这里以供参考：

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还利用ResponseEntity<>返回，并成功地返回了正确的JSON有效负载。

Answer 1

我不知道确切的答案是什么，但可能问题出在JSON配置上。首先，您的@Controller不是@RestController，您没有显式指定生成的内容。我希望你在请求中这样做，这样spring就知道该怎么做了。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方法支持尝试在这里捕获代码。检查哪个转换器返回true。如果有多个条件通过，则Spring使用第一个条件。通过stacktrace，您还可以找到哪些转换器可以满足您的请求，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#支持-java.lang.class-