[springmvc] Exception Handling

1. @Controller level

　　Annotate a separate method in your @Controller as a @ExceptionHandler

　　simply catch the Exception yourself in your handler method

2. DispatcherServlet level

　　Rely on the DefaultHandlerExceptionResolver:Maps common exceptions to appropriate status codes

　　Supplement with your own custom HandlerExceptionResolver as needed

    @ExceptionHandler
    public @ResponseBody String handle(IllegalStateException e) {
        return "IllegalStateException handled!";
    }
    
    @RequestMapping("/exception")
    public @ResponseBody String exception() {
        throw new IllegalStateException("Sorry!");
    }