Proper usage of Apache HttpClient and when to close it.

Question

I am using HttpClient within a servlet to make calls to a resource which I return as the servlets response after some manipulation.

My HttpClient uses PoolingHttpClientConnectionManager.

I create the client like so:

private CloseableHttpClient getConfiguredHttpClient(){
    return HttpClientBuilder
        .create()
        .setDefaultRequestConfig(config)
        .setConnectionReuseStrategy(NoConnectionReuseStrategy.INSTANCE)
        .setConnectionManagerShared(true)
        .setConnectionManager(connManager)
        .build();
}

I use this client within a Try With Resource within the servlets service method, so it is auto closed. To stop the the connection manager from being closed, I set setConnectionManagerShared to true.

I have seen other code samples that do not close the HttpClient. Should I not be closing this resource?

Thanks

Answer 1

For httpcomponents version 4.5.x:

I found that you really need to close the resource as shown in the documentation: https://hc.apache.org/httpcomponents-client-4.5.x/quickstart.html

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();
    EntityUtils.consume(entity1);
} finally {
    response1.close();
}

Answer 2

For other versions of httpcomponents, see other answers.

For older versions of httpcomponents (http://hc.apache.org/httpcomponents-client-4.2.x/quickstart.html):

You do not need to explicitly close the HttpClient, however, (you may be doing this already but worth noting) you should ensure that connections are released after method execution.

Edit: The ClientConnectionManager within the HttpClient is going to be responsible for maintaining the state of connections.

 GetMethod httpget = new GetMethod("http://www.url.com/");
  try {
    httpclient.executeMethod(httpget);
    Reader reader = new InputStreamReader(httpget.getResponseBodyAsStream(), httpget.getResponseCharSet()); 
    // consume the response entity and do something awesome
  } finally {
    httpget.releaseConnection();
  }