Nested Exception handling in Spring MVC

Question

I am getting the following error:

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException

And to handle this in a controller, I have used the following code:

@ExceptionHandler(NestedServletException.class)
public ModelAndView handleServletErrors(){
    System.out.println("Servlet Exception is thrown");
    ModelAndView mv = new ModelAndView("error"); 
    mv.addObject("error", "Error encountered while processing reqeust.");
    return mv;
}

But this does not handle the exception thrown above. Whereas if I use NullPointerException class instead of NestedServletException , it works. Since Spring is throwing exception in response to NullPointerException shouldn't it be handled by the code above?

Answer 1

Quoting the documentation of @ExceptionHandler :

Annotation for handling exceptions in specific handler classes and/or handler methods.

This annotation will allow a method to handle exceptions that are thrown by handler methods, ie methods that are annotated with @RequestMapping . Quoting the Spring reference :

You can do that with @ExceptionHandler methods. When declared within a controller such methods apply to exceptions raised by @RequestMapping methods of that contoroller (or any of its sub-classes). You can also declare an @ExceptionHandler method within an @ControllerAdvice class in which case it handles exceptions from @RequestMapping methods from many controllers.

Since the exception thrown by your handler is NullPointerException , the exception handler method will handle that specific exception. It will not handle the generic NestedServletException that Spring uses to encapsulate servlet exceptions.