HttpComponents 也就是以前的httpclient项目，可以用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端/服务器编程工具包，并且它支持 HTTP 协议最新的版本和建议。不过现在的 HttpComponents 包含多个子项目，有：

HttpComponents Core

HttpComponents Client

HttpComponents AsyncClient

Commons HttpClient

以下列出的是 HttpClient 提供的主要的功能，要知道更多详细的功能可以参见 HttpClient 的主页。

实现了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）

支持自动转向

支持 HTTPS 协议

支持代理服务器等

支持Cookie

HttpClient 示例代码：

DefaultHttpClient httpclient = new DefaultHttpClient();

try {

HttpGet httpget = new HttpGet("https://portal.sun.com/portal/dt");

HttpResponse response = httpclient.execute(httpget);

HttpEntity entity = response.getEntity();

System.out.println("Login form get: " + response.getStatusLine());

EntityUtils.consume(entity);

System.out.println("Initial set of cookies:");

List cookies = httpclient.getCookieStore().getCookies();

if (cookies.isEmpty()) {

System.out.println("None");

} else {

for (int i = 0; i < cookies.size(); i++) {

System.out.println("- " + cookies.get(i).toString());

}

}

HttpPost httpost = new HttpPost("https://portal.sun.com/amserver/UI/Login?" +

"org=self_registered_users&" +

"goto=/portal/dt&" +

"gotoOnFail=/portal/dt?error=true");

List nvps = new ArrayList ();

nvps.add(new BasicNameValuePair("IDToken1", "username"));

nvps.add(new BasicNameValuePair("IDToken2", "password"));

httpost.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8));

response = httpclient.execute(httpost);

entity = response.getEntity();

System.out.println("Login form get: " + response.getStatusLine());

EntityUtils.consume(entity);

System.out.println("Post logon cookies:");

cookies = httpclient.getCookieStore().getCookies();

if (cookies.isEmpty()) {

System.out.println("None");

} else {

for (int i = 0; i < cookies.size(); i++) {

System.out.println("- " + cookies.get(i).toString());

}

}

} finally {

// When HttpClient instance is no longer needed,

// shut down the connection manager to ensure

// immediate deallocation of all system resources

httpclient.getConnectionManager().shutdown();

}