Spring MVC REST Handing Bad Url (404) by returning JSON

Question

I am developing a REST service using SpringMVC, where I have @RequestMapping at class and method level.

This application is currently configured to return error-page js

Answer 1

After digging around DispatcherServlet and HttpServletBean.init() in SpringFramework I see that its possible in Spring 4.

org.springframework.web.servlet.DispatcherServlet

/** Throw a NoHandlerFoundException if no Handler was found to process this request? **/
private boolean throwExceptionIfNoHandlerFound = false;

protected void noHandlerFound(HttpServletRequest request, HttpServletResponse response) throws Exception {
    if (pageNotFoundLogger.isWarnEnabled()) {
        String requestUri = urlPathHelper.getRequestUri(request);
        pageNotFoundLogger.warn("No mapping found for HTTP request with URI [" + requestUri +
                "] in DispatcherServlet with name '" + getServletName() + "'");
    }
    if(throwExceptionIfNoHandlerFound) {
        ServletServerHttpRequest req = new ServletServerHttpRequest(request);
        throw new NoHandlerFoundException(req.getMethod().name(),
                req.getServletRequest().getRequestURI(),req.getHeaders());
    } else {
        response.sendError(HttpServletResponse.SC_NOT_FOUND);
    }
}

throwExceptionIfNoHandlerFound is false by default and we should enable that in web.xml

    appServlet
    org.springframework.web.servlet.DispatcherServlet
        
            throwExceptionIfNoHandlerFound
            true
        
    1
    true

And then you can catch it in a class annotated with @ControllerAdvice using this method.

@ExceptionHandler(NoHandlerFoundException.class)
@ResponseStatus(value=HttpStatus.NOT_FOUND)
@ResponseBody
public ResponseEntity requestHandlingNoHandlerFound(HttpServletRequest req, NoHandlerFoundException ex) {
    Locale locale = LocaleContextHolder.getLocale();
    String errorMessage = messageSource.getMessage("error.bad.url", null, locale);

    String errorURL = req.getRequestURL().toString();

    ErrorInfo errorInfo = new ErrorInfo(errorURL, errorMessage);
    return new ResponseEntity(errorInfo.toJson(), HttpStatus.BAD_REQUEST);
}

Which allows me to return JSON response for bad URLs for which no mapping exist, instead of redirecting to a JSP page :)

{"message":"URL does not exist","url":"http://localhost:8080/service/patientssd"}