rest - Spring @ExceptionHandler does not work with @ResponseBody

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");
}

Anyone?

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()));
}