Read error response body in Java

Question

In Java, this code throws an exception when the HTTP result is 404 range:

URL url = new URL("http://stackoverflow.com/asdf404notfound"); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.getInputStream(); // throws! 

In my case, I happen to know that the content is 404, but I'd still like to read the body of the response anyway.

(In my actual case the response code is 403, but the body of the response explains the reason for rejection, and I'd like to display that to the user.)

How can I access the response body?

Answer 1

Here is the bug report (close, will not fix, not a bug).

Their advice there is to code like this:

HttpURLConnection httpConn = (HttpURLConnection)_urlConnection; InputStream _is; if (httpConn.getResponseCode() < HttpURLConnection.HTTP_BAD_REQUEST) {     _is = httpConn.getInputStream(); } else {      /* error from server */     _is = httpConn.getErrorStream(); } 

Answer 2

It's the same problem I was having: HttpUrlConnection returns FileNotFoundException if you try to read the getInputStream() from the connection.
You should instead use getErrorStream() when the status code is higher than 400.

More than this, please be careful since it's not only 200 to be the success status code, even 201, 204, etc. are often used as success statuses.

Here is an example of how I went to manage it

... connection code code code ...  // Get the response code  int statusCode = connection.getResponseCode();  InputStream is = null;  if (statusCode >= 200 && statusCode < 400) {    // Create an InputStream in order to extract the response object    is = connection.getInputStream(); } else {    is = connection.getErrorStream(); }  ... callback/response to your handler.... 

In this way, you'll be able to get the needed response in both success and error cases.

Hope this helps!