HttpClient-Quick-Start.md

HttpClient Quick Start

1. 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.

2. HttpClient 4.5 requires Java 1.5 or newer.

3. 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

4. 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

5. HttpClient Examples - a set of examples demonstrating some of the more complex behavior.

6. 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

7. 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.