Apache HttpClient - Closing Connection


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If you are processing HTTP responses manually instead of using a response handler, you need to close all the http connections by yourself. This chapter explains how to close the connections manually.

While closing HTTP connections manually follow the steps given below −

Step 1 - Create an HttpClient object

The createDefault() method of the HttpClients class returns an object of the class CloseableHttpClient, which is the base implementation of the HttpClient interface.

Using this method, create an HttpClient object as shown below −

CloseableHttpClient httpClient = HttpClients.createDefault();

Step 2 - Start a try-finally block

Start a try-finally block, write the remaining code in the programs in the try block and close the CloseableHttpClient object in the finally block.

CloseableHttpClient httpClient = HttpClients.createDefault();
try{
   //Remaining code . . . . . . . . . . . . . . .
}finally{
   httpClient.close();
}

Step 3 - Create a HttpGetobject

The HttpGet class represents the HTTP GET request which retrieves the information of the given server using a URI.

Create a HTTP GET request by instantiating the HttpGet class by passing a string representing the URI.

HttpGet httpGet = new HttpGet("http://www.tutorialspoint.com/");

Step 4 - Execute the Get request

The execute() method of the CloseableHttpClient object accepts a HttpUriRequest (interface) object (i.e. HttpGet, HttpPost, HttpPut, HttpHead etc.) and returns a response object.

Execute the request using the given method −

HttpResponse httpResponse = httpclient.execute(httpGet);

Step 5 - Start another (nested) try-finally

Start another try-finally block (nested within the previous try-finally), write the remaining code in the programs in this try block and close the HttpResponse object in the finally block.

CloseableHttpClient httpclient = HttpClients.createDefault();
try{
   . . . . . . .
   . . . . . . .
   CloseableHttpResponse httpresponse = httpclient.execute(httpget);
   try{
      . . . . . . .
      . . . . . . .
   }finally{
      httpresponse.close();
   }
}finally{
   httpclient.close();
}

Example

Whenever you create/obtain objects such as request, response stream, etc., start a try finally block in the next line, write the remaining code within the try and close the respective object in the finally block as demonstrated in the following program −

import java.util.Scanner;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;

public class CloseConnectionExample {
   
   public static void main(String args[])throws Exception{
 
      //Create an HttpClient object
      CloseableHttpClient httpclient = HttpClients.createDefault();

      try{
         //Create an HttpGet object
         HttpGet httpget = new HttpGet("http://www.tutorialspoint.com/");

         //Execute the Get request
         CloseableHttpResponse httpresponse = httpclient.execute(httpget);

         try{
            Scanner sc = new Scanner(httpresponse.getEntity().getContent());
            while(sc.hasNext()) {
               System.out.println(sc.nextLine());
            }
         }finally{
            httpresponse.close();
         }
      }finally{
         httpclient.close();
      }
   }
}

Output

On executing the above program, the following output is generated −

<!DOCTYPE html>
<!--[if IE 8]><html class = "ie ie8"> <![endif]-->
<!--[if IE 9]><html class = "ie ie9"> <![endif]-->
<!--[if gt IE 9]><!-->
<html lang = "en-US"> <!--<![endif]-->
<head>
<!-- Basic -->
<meta charset = "utf-8">
<meta http-equiv = "X-UA-Compatible" content = "IE = edge">
<meta name = "viewport" content = "width = device-width,initial-scale = 1.0,userscalable = yes">
<link href = "https://cdn.muicss.com/mui-0.9.39/extra/mui-rem.min.css"
rel = "stylesheet" type = "text/css" />
<link rel = "stylesheet" href = "/questions/css/home.css?v = 3" />
<script src = "/questions/js/jquery.min.js"></script>
<script src = "/questions/js/fontawesome.js"></script>
<script src = "https://cdn.muicss.com/mui-0.9.39/js/mui.min.js"></script>
</head>
. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . 
<script>
window.dataLayer = window.dataLayer || [];
function gtag() {dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'UA-232293-17');
</script>
</body>
</html>
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