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();
    }
    

Source can be downloaded here

  • 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();
    

Source can be downloaded here

  • 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.