How can I return an error message and HTTP status code that calls jQuery AJAX error function?

Question

Using Spring, I have a SimpleMappingExceptionResolver that catches any unexpected exceptions in my application in the resolveException method. In the method, I return a ModelAndView that gives error message text back to the HTTP client. Here's the code:

public class UnExpectedExceptionResolver extends SimpleMappingExceptionResolver {

private Log logger = LogFactory.getLog(this.getClass().getName());
private ResourceBundleMessageSource messageSource;

@Override
public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception exception) {

    // let the end user know that an error occurred
    Locale locale = RequestContextUtils.getLocale(request);
    String messageText = messageSource.getMessage("systemError", null, locale);
    Message message = new Message(messageText, MessageType.ERROR);
    ModelAndView mav = new ModelAndView();
    mav.setView(new MappingJacksonJsonView());
    mav.addObject("message", message);
    return mav;
}

As such, the response is returned with a HTTP status code of 200 with response text being the message (JSON). Unfortunately, the client thinks it's a valid response due to the 200 code and tries to process it as such. I tried setting the HTTP status code to 500 as follows:

 response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Server Error");

right before the

 return mav;

statement. Unfortunately, this returns a HTML page indicating a internal error instead of my JSON message. How can I return the JSON message and still indicate a server error (or some type of error) to the client? Specifically, I expect the client's error function in the AJAX call to be invoked and still have the message data sent back to the client. FYI - I'm using jQuery on the client side.

Solution 1

I don't know how exactly you are making the requests to the server. But this is how I would do it.

@ExceptionHandler(Exception.class)
@ResponseStatus(value = HttpStatus.INTERNAL_SERVER_ERROR, reason = "your message")
public void handleException(IllegalStateException ex, HttpServletResponse response) throws IOException
{
}

In in the client side

$.ajax({
type : "POST",
url : urlString,
data : params,
dataType : 'json',
success : function(data) {
    //  do something}
error: function (xhr, ajaxOptions, thrownError) {
    alert(xhr.status); //This will be 500
    alert(xhr.responseText); // your message
    //do stuff
  }

Solution 2

In Spring 3.2 you can put your exception handler inside a @ControllerAdvice annotated class.

From Spring 3.2 documenation

Classes annotated with @ControllerAdvice can contain @ExceptionHandler, @InitBinder, and @ModelAttribute methods and those will apply to @RequestMapping methods across controller hierarchies as opposed to the controller hierarchy within which they are declared. @ControllerAdvice is a component annotation allowing implementation classes to be auto-detected through classpath scanning.

So if your controllers are picked up by autoscanning @Controller annotated classes, @ControllerAdvice should also work(if you scan @Controller classes with an explicit annotation expression, you may need to register this bean separately).

@ControllerAdvice
public class AppControllerAdvice{
        @ExceptionHandler(Throwable.class)
        ResponseEntity<String> customHandler(Exception ex) {
        return new ResponseEntity<String>(
                "Custom user message",
                HttpStatus.INTERNAL_SERVER_ERROR);

} 

Please note that the text is a part of the returned entity and not an HTTP reason phrase.

Solution 3

Here is how I did it.

public class CustomExceptionResolver extends AbstractHandlerExceptionResolver {

    private static final Logger logger = Logger.getLogger(CustomExceptionResolver.class);

    protected ModelAndView doResolveException(HttpServletRequest request,
                                              HttpServletResponse response,
                                              Object handler,
                                              Exception ex) {
        try {
            response.reset();
            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            response.setCharacterEncoding("UTF-8");
            response.setContentType("text/json");
            MappingJacksonJsonView view = new MappingJacksonJsonView();
            Map<String, String> asd = new HashMap<String, String>();
            asd.put("message", ex.getMessage());
            view.setAttributesMap(asd);
            return new ModelAndView(view);
        } catch (Exception e) {
            logger.error("send back error status and message : " + ex.getMessage(), e);
        }
        return null;
    }

And then of course in my json-servlet.xml file:

<bean id="exceptionResolver" class="com.autolytix.common.web.CustomExceptionResolver"/>