What's the difference between CloseableHttpResponse.close() and httpPost.releaseConnection()?

Question

CloseableHttpResponse response = null; try {     // do some thing ....     HttpPost request = new HttpPost("some url");     response = getHttpClient().execute(request);     // do some other thing .... } catch(Exception e) {     // deal with exception } finally {     if(response != null) {         try {             response.close(); // (1)         } catch(Exception e) {}         request.releaseConnection(); // (2)     } } 

I've made a http request like above.

In order to release the underlying connection, is it correct to call (1) and (2)? and what's the difference between the two invocation?

Answer 1

Short answer:

request.releaseConnection() is releasing the underlying HTTP connection to allow it to be reused. response.close() is closing a stream (not a connection), this stream is the response content we are streaming from the network socket.

Long Answer:

The correct pattern to follow in any recent version > 4.2 and probably even before that, is not to use releaseConnection.

request.releaseConnection() releases the underlying httpConnection so the request can be reused, however the Java doc says:

A convenience method to simplify migration from HttpClient 3.1 API...

Instead of releasing the connection, we ensure the response content is fully consumed which in turn ensures the connection is released and ready for reuse. A short example is shown below:

CloseableHttpClient httpclient = HttpClients.createDefault(); HttpGet httpGet = new HttpGet("http://targethost/homepage"); CloseableHttpResponse response1 = httpclient.execute(httpGet); try {     System.out.println(response1.getStatusLine());     HttpEntity entity1 = response1.getEntity();     // do something useful with the response body     String bodyAsString = EntityUtils.toString(exportResponse.getEntity());     System.out.println(bodyAsString);     // and ensure it is fully consumed (this is how stream is released.     EntityUtils.consume(entity1); } finally {     response1.close(); }