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("");
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<Cookie> 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("" +
"org=self_registered_users&" +
"goto=/portal/dt&" +
"gotoOnFail=/portal/dt?error=true");
List <NameValuePair> nvps = new ArrayList <NameValuePair>();
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();
}