显示Spring使用JSP处理的异常消息

Question

I'm new in Spring and also in JSP. I'm working in the project and I needed to create a page where application will be redirected in case of specific exceptions. I have service's method which throws one of exceptions. This method is called in one of our page controller with @RequestMapping annotation. So to redirect to specific error page, I created two methods with @ExceptionHanlder which handle this exceptions in this controller. How it looks:

@ExceptionHandler(IllegalStateException.class)
public ModelAndView handleIllegalStateException (IllegalStateException ex) {
    ModelAndView modelAndView =  new ModelAndView("redirect:/error");
    modelAndView.addObject("exceptionMsg", ex.getMessage());
    return modelAndView;
}

But there wasn't enough. I also need to create ErrorPageController:

@Controller
@RequestMapping("/error")
public class ErrorPageController {
    @RequestMapping(method = RequestMethod.GET)
    public ModelAndView displayErrorPage() {
        return new ModelAndView("error");
    }
}

And now works displaying error page. But my problem is, that I can't display error message in JSP... I have:

<h3>Error page: "${exceptionMsg}"</h3>

But I don't see a message ;/ Instead of it, I see message in URL:

localhost/error?exceptionMsg=Cannot+change+participation+status+if+the+event+is+cancelled+or+it+has+ended.

And it's wrong because in URL I want to have only an "localhost/error" and nothing more. This message I want to display in JSP.

Answer 1

To fix both of your issues (show the message, and have the proper url) you should in original code change you exception handler method to eg

@ExceptionHandler(IllegalStateException.class)
public RedirectView handleIllegalStateException(IllegalStateException ex, HttpServletRequest request) {
    RedirectView rw = new RedirectView("/error");
    FlashMap outputFlashMap = RequestContextUtils.getOutputFlashMap(request);
    if (outputFlashMap != null) {
        outputFlashMap.put("exceptionMsg", ex.getMessage());
    }
    return rw;
}

Why? If you want your attributes to persist through redirect, you need to add them to flash scope. The code above uses the FlashMap, from the docs

A FlashMap is saved before the redirect (typically in the session) and is made available after the redirect and removed immediately.

If it were to be a normal controller method, you could have simply added RedirectAttributes as an argument, but on @ExceptionHandler methods, the arguments of RedirectAttributes are not resolved, so you need to add the HttpServletRequest and use the RedirectView.

Answer 2

You have to change ModelAndView to:

@ExceptionHandler(IllegalStateException.class)
public ModelAndView handleIllegalStateException (IllegalStateException ex) {
    ModelAndView modelAndView =  new ModelAndView("error");
    modelAndView.addObject("exceptionMsg", ex.getMessage());
    return modelAndView;
}

And have this part in error.jsp:

<h3>Error page: "${exceptionMsg}"</h3>