Safe use of HttpURLConnection

Question

When using HttpURLConnection does the InputStream need to be closed if we do not 'get' and use it?

i.e. is this safe?

HttpURLConnection conn = (HttpURLConnection) uri.getURI().toURL().openConnection(); conn.connect(); // check for content type I don't care about if (conn.getContentType.equals("image/gif") return;  // get stream and read from it InputStream is = conn.getInputStream(); try {     // read from is } finally {     is.close(); } 

Secondly, is it safe to close an InputStream before all of it's content has been fully read?

Is there a risk of leaving the underlying socket in ESTABLISHED or even CLOSE_WAIT state?

Answer 1

According to http://docs.oracle.com/javase/6/docs/technotes/guides/net/http-keepalive.html and OpenJDK source code.

(When keepAlive == true)

If client called HttpURLConnection.getInputSteam().close(), the later call to HttpURLConnection.disconnect() will NOT close the Socket. i.e. The Socket is reused (cached)

If client does not call close(), call disconnect() will close the InputStream and close the Socket.

So in order to reuse the Socket, just call InputStream.close(). Do not call HttpURLConnection.disconnect().

Answer 2

is it safe to close an InputStream before all of it's content has been read

You need to read all of the data in the input stream before you close it so that the underlying TCP connection gets cached. I have read that it should not be required in latest Java, but it was always mandated to read the whole response for connection re-use.

Check this post: keep-alive in java6