Spring #ExceptionHandler does not work with #ResponseBody - rest

Question

I try to configure a spring exception handler for a rest controller that is able to render a map to both xml and json based on the incoming accept header. It throws a 500 servlet exception right now.
This works, it picks up the home.jsp:
#ExceptionHandler(IllegalArgumentException.class)
public String handleException(final Exception e, final HttpServletRequest request, Writer writer)
{
return "home";
}
This does not work:
#ExceptionHandler(IllegalArgumentException.class)
public #ResponseBody Map<String, Object> handleException(final Exception e, final HttpServletRequest request, Writer writer)
{
final Map<String, Object> map = new HashMap<String, Object>();
map.put("errorCode", 1234);
map.put("errorMessage", "Some error message");
return map;
}
In the same controller mapping the response to xml or json via the respective converter works:
#RequestMapping(method = RequestMethod.GET, value = "/book/{id}", headers = "Accept=application/json,application/xml")
public #ResponseBody
Book getBook(#PathVariable final String id)
{
logger.warn("id=" + id);
return new Book("12345", new Date(), "Sven Haiges");
}

Answer 1

Your method
#ExceptionHandler(IllegalArgumentException.class)
public #ResponseBody Map<String, Object> handleException(final Exception e, final HttpServletRequest request, Writer writer)
does not work because it has the wrong return type. #ExceptionHandler methods have only two valid return types:
String
ModelAndView.
See http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/mvc.html for more information. Here's the specific text from the link:
The return type can be a String, which
is interpreted as a view name or a
ModelAndView object.
In response to the comment
Thanx, seems I overread this. That's
bad... any ideas how to provides
exceptions automatically in xml/json
format? – Sven Haiges 7 hours ago
Here's what I've done (I've actually done it in Scala so I'm not sure if the syntax is exactly correct, but you should get the gist).
#ExceptionHandler(Throwable.class)
#ResponseBody
public void handleException(final Exception e, final HttpServletRequest request,
Writer writer)
{
writer.write(String.format(
"{\"error\":{\"java.class\":\"%s\", \"message\":\"%s\"}}",
e.getClass(), e.getMessage()));
}

Answer 2

Thanx, seems I overread this. That's bad... any ideas how to provides
exceptions automatically in xml/json format?
New in Spring 3.0 MappingJacksonJsonView can be utilized to achieve that:
private MappingJacksonJsonView jsonView = new MappingJacksonJsonView();
#ExceptionHandler(Exception.class)
public ModelAndView handleAnyException( Exception ex )
{
return new ModelAndView( jsonView, "error", new ErrorMessage( ex ) );
}

Answer 3

This seems ilke a confirmed Bug (SPR-6902
#ResponseBody does not work with #ExceptionHandler)
https://jira.springsource.org/browse/SPR-6902
Fixed in 3.1 M1 though...

Answer 4

The following could be a workaround if you are using message converters to marshall error objects as the response content
#ExceptionHandler(IllegalArgumentException.class)
public String handleException(final Exception e, final HttpServletRequest request)
{
final Map<String, Object> map = new HashMap<String, Object>();
map.put("errorCode", 1234);
map.put("errorMessage", "Some error message");
request.setAttribute("error", map);
return "forward:/book/errors"; //forward to url for generic errors
}
//set the response status and return the error object to be marshalled
#SuppressWarnings("unchecked")
#RequestMapping(value = {"/book/errors"}, method = {RequestMethod.POST, RequestMethod.GET})
public #ResponseBody Map<String, Object> showError(HttpServletRequest request, HttpServletResponse response){
Map<String, Object> map = new HashMap<String, Object>();
if(request.getAttribute("error") != null)
map = (Map<String, Object>) request.getAttribute("error");
response.setStatus(Integer.parseInt(map.get("errorCode").toString()));
return map;
}

Answer 5

I am using Spring 3.2.4. My solution to the problem was to make sure that the object I was returning from the exception handler had getters.
Without getters Jackson was unable to serialize the object to JSON.
In my code, for the following ExceptionHandler:
#ExceptionHandler(RuntimeException.class)
#ResponseBody
public List<ErrorInfo> exceptionHandler(Exception exception){
return ((ConversionException) exception).getErrorInfos();
}
I needed to make sure my ErrorInfo object had getters:
package com.pelletier.valuelist.exception;
public class ErrorInfo {
private int code;
private String field;
private RuntimeException exception;
public ErrorInfo(){}
public ErrorInfo(int code, String field, RuntimeException exception){
this.code = code;
this.field = field;
this.exception = exception;
}
public int getCode() {
return code;
}
public String getField() {
return field;
}
public String getException() {
return exception.getMessage();
}
}

Answer 6

AnnotationMethodHandlerExceptionResolver also need MappingJacksonHttpMessageConverter
<bean
class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver">
<property name="messageConverters">
<list>
<bean
class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
<property name="objectMapper" ref="jacksonObjectMapper" />
</bean>
</list>
</property>
</bean>
<bean id="jacksonObjectMapper"
class="iacm.cemetery.framework.web.servlet.rest.JacksonObjectMapper" />

Answer 7

I faced the similar issue, this problem occurs when your Controller method return type and ExceptionHandler return types are not same. Make sure you have exactly same return types.
Controller method:
#RequestMapping(value = "/{id}", produces = "application/json", method = RequestMethod.POST)
public ResponseEntity<?> getUserById(#PathVariable String id) throws NotFoundException {
String response = userService.getUser(id);
return new ResponseEntity(response, HttpStatus.OK);
}
Advice method:
#ExceptionHandler(NotFoundException.class)
public ResponseEntity<?> notFoundException(HttpServletRequest request, NotFoundException e) {
ExceptionResponse response = new ExceptionResponse();
response.setSuccess(false);
response.setMessage(e.getMessage());
return new ResponseEntity(response, HttpStatus.NOT_FOUND);
}
As you can see return types in both the classes are same ResponseEntity<?>.