[FIXED] Intercept @RequestHeader exception for missing header

Issue

I have a method in controller with has parameter for example

@RequestMapping(value = "/{blabla}", method = RequestMethod.POST)
@ResponseStatus(HttpStatus.CREATED)
public void post(@RequestHeader("ETag") int etag)

If there is no ETag header in request - client gets 400 (BAD_REQUEST), which is not any informative. I need to somehow handle this exception and send my own exception to client (I use JSON for this purpose). I know that I can intercept exception via @ExceptionHandler, but in that case all HTTP 400 requests will be handled, but I want that have missing ETag in headers. Any ideas?

Solution

You should user an @ExceptionHandler method that looks if ETag header is present and takes appropriate action :

@ExceptionHandler(UnsatisfiedServletRequestParameterException.class)
public onErr400(@RequestHeader(value="ETag", required=false) String ETag,
        UnsatisfiedServletRequestParameterException ex) {
    if(ETag == null) {
        // Ok the problem was ETag Header : give your informational message
    } else {
        // It is another error 400  : simply say request is incorrect or use ex
    }
}

Answered By - Serge Ballesta