HttpClient Authentication Doument:
http://hc.apache.org/httpclient-3.x/authentication.html
HttpClient支持使用代理服务器以及身份认证
1、代理服务器的设置很简单：
HttpClient client = new HttpClient();
client.getHostConfiguration().setProxy(host, port);
2、身份验证：
HttpClient client = new HttpClient();
client.getParams().setAuthenticationPreemptive(true);
Credentials defaultcreds = new UsernamePasswordCredentials("username", "password");
client.getState().setCredentials(AuthScope.ANY, defaultcreds);