HttpClient Quick Start

• Download ‘Binary’ package of the latest HttpClient 4.5 release or configure dependency on HttpClient and Fluent HC modules using a dependency manager of your choice as described here.

• HttpClient 4.5 requires Java 1.6 or newer.

• The below code fragment illustrates the execution of HTTP GET and POST requests using the HttpClient native API.

  CloseableHttpClient httpclient = HttpClients.createDefault();
  HttpGet httpGet = new HttpGet("http://targethost/homepage");
  CloseableHttpResponse response1 = httpclient.execute(httpGet);
  // The underlying HTTP connection is still held by the response object
  // to allow the response content to be streamed directly from the network socket.
  // In order to ensure correct deallocation of system resources
  // the user MUST call CloseableHttpResponse#close() from a finally clause.
  // Please note that if response content is not fully consumed the underlying
  // connection cannot be safely re-used and will be shut down and discarded
  // by the connection manager. 
  try {
      System.out.println(response1.getStatusLine());
      HttpEntity entity1 = response1.getEntity();
      // do something useful with the response body
      // and ensure it is fully consumed
      EntityUtils.consume(entity1);
  } finally {
      response1.close();
  }
  
  HttpPost httpPost = new HttpPost("http://targethost/login");
  List <NameValuePair> nvps = new ArrayList <NameValuePair>();
  nvps.add(new BasicNameValuePair("username", "vip"));
  nvps.add(new BasicNameValuePair("password", "secret"));
  httpPost.setEntity(new UrlEncodedFormEntity(nvps));
  CloseableHttpResponse response2 = httpclient.execute(httpPost);
  
  try {
      System.out.println(response2.getStatusLine());
      HttpEntity entity2 = response2.getEntity();
      // do something useful with the response body
      // and ensure it is fully consumed
      EntityUtils.consume(entity2);
  } finally {
      response2.close();
  }
  

• The same requests can be executed using a simpler, albeit less flexible, fluent API.

  // The fluent API relieves the user from having to deal with manual deallocation of system
  // resources at the cost of having to buffer response content in memory in some cases.
  
  Request.Get("http://targethost/homepage")
      .execute().returnContent();
  Request.Post("http://targethost/login")
      .bodyForm(Form.form().add("username",  "vip").add("password",  "secret").build())
      .execute().returnContent();
  

• HttpClient Examples - a set of examples demonstrating some of the more complex scenarios.

• HttpClient Tutorial - gives a detailed examination of the HttpClient API, which was written in close accordance with the (sometimes not very intuitive) HTTP specification/standard. A copy is also shipped with the release.
  A PDF version is also available.

• HttpClient Primer - explains the scope of HttpClient. Note that HttpClient is not a browser. It lacks the UI, HTML renderer and a JavaScript engine that a browser will possess.