Spring Exception Handling:
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Using HTTP Status Codes

Normally any unhandled exception thrown when processing a web-request causes the server to return an HTTP 500 response. However, any exception that you write yourself can be annotated with the @ResponseStatus annotation (which supports all the HTTP status codes defined by the HTTP specification). When an annotated exception is thrown from a controller method, and not handled elsewhere, it will automatically cause the appropriate HTTP response to be returned with the specified status-code.

For example, here is an exception for a missing order.

 @ResponseStatus(value=HttpStatus.NOT_FOUND, reason="No such Order")  // 404
 public class OrderNotFoundException extends RuntimeException {
     // ...
 }

And here is a controller method using it:

 @RequestMapping(value="/orders/{id}", method=GET)
 public String showOrder(@PathVariable("id") long id, Model model) {
     Order order = orderRepository.findOrderById(id);

     if (order == null) throw new OrderNotFoundException(id);

     model.addAttribute(order);
     return "orderDetail";
 }

A familiar HTTP 404 response will be returned if the URL handled by this method includes an unknown order id.

Controller Based Exception Handling

Using @ExceptionHandler

You can add extra (@ExceptionHandler) methods to any controller to specifically handle exceptions thrown by request handling (@RequestMapping) methods in the same controller. Such methods can:

1. Handle exceptions without the @ResponseStatus annotation (typically predefined exceptions that you didn’t write)
2. Redirect the user to a dedicated error view
3. Build a totally custom error response