FileNotFoundException while getting the InputStream object from HttpURLConnection

I don't know about your Spring/JAXB combination, but the average REST webservice won't return a response body on POST/PUT, just a response status. You'd like to determine it instead of the body.

Replace

InputStream response = con.getInputStream();

by

int status = con.getResponseCode();

All available status codes and their meaning are available in the HTTP spec, as linked before. The webservice itself should also come along with some documentation which overviews all status codes supported by the webservice and their special meaning, if any.

If the status starts with 4nn or 5nn, you'd like to use getErrorStream() instead to read the response body which may contain the error details.

InputStream error = con.getErrorStream();

FileNotFound is just an unfortunate exception used to indicate that the web server returned a 404.

To anyone with this problem in the future, the reason is because the status code was a 404 (or in my case was a 500). It appears the InpuStream function will throw an error when the status code is not 200.

In my case I control my own server and was returning a 500 status code to indicate an error occurred. Despite me also sending a body with a string message detailing the error, the inputstream threw an error regardless of the body being completely readable.

If you control your server I suppose this can be handled by sending yourself a 200 status code and then handling whatever the string error response was.