此处所用HttpClient版本是4.5，在HttpClient的实例化过程中可能会有人遇到不能实例化的问题，因为在3.x版本中HttpClient是个类，而在4.x版本中变成了接口，下面是4.x版本的使用实例。
所需jar包httpclient-4.5.1.jar、httpcore-4.4.1.jar、httpmime-4.5.jar，这三个是必需的，但在使用过程中发现也需要commons-logging.jar包，因此有四个jar包需要导入。
代码示例：
import java.io.IOException; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.client.ClientProtocolException; import org.apache.http.client.methods.HttpPost; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; public class Client4 { public static void main(String[] args) { // 创建默认的客户端实例 CloseableHttpClient httpCLient = HttpClients.createDefault(); // 创建get请求实例 HttpPost httpost = new HttpPost("http://www.baidu.com"); try { // 客户端执行post请求 返回响应实体 HttpResponse response = httpCLient.execute(httpost); // 服务器响应状态行 // System.out.println(response.getStatusLine()); // Header[] heads = response.getAllHeaders(); // // 打印所有响应头 // for(Header h:heads){ // System.out.println(h.getName()+":"+h.getValue()); // } // 获取响应消息实体 HttpEntity entity = response.getEntity(); if(entity != null){ //响应内容 System.out.println(EntityUtils.toString(entity)); } } catch (ClientProtocolException e){ e.printStackTrace(); } catch (IOException e){ e.printStackTrace(); }finally{ try { if(httpCLient!=null){ httpCLient.close(); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }
输出的结果如下：
<!DOCTYPE html>
<!--STATUS OK--><html> <head><meta http-equiv=content-type content=text/html;charset=utf-8><meta http-equiv=X-UA-Compatible content=IE=Edge><meta content=always name=referrer><link rel=stylesheet type=text/css href=http://s1.bdstatic.com/r/www/cache/bdorz/baidu.min.css><title>百度一下，你就知道</title></head> <body link=#0000cc> <div id=wrapper> <div id=head> <div class=head_wrapper> <div class=s_form> <div class=s_form_wrapper> <div id=lg> <img hidefocus=true src=//www.baidu.com/img/bd_logo1.png width=270 height=129> </div> <form id=form name=f action=//www.baidu.com/s class=fm> <input type=hidden name=bdorz_come value=1> <input type=hidden name=ie value=utf-8> <input type=hidden name=f value=8> <input type=hidden name=rsv_bp value=1> <input type=hidden name=rsv_idx value=1> <input type=hidden name=tn value=baidu><span class="bg s_ipt_wr"><input id=kw name=wd class=s_ipt value maxlength=255 autocomplete=off autofocus></span><span class="bg s_btn_wr"><input type=submit id=su value=百度一下 class="bg s_btn"></span> </form> </div> </div> <div id=u1> <a href=http://news.baidu.com name=tj_trnews class=mnav>新闻</a> <a href=http://www.hao123.com name=tj_trhao123 class=mnav>hao123</a> <a href=http://map.baidu.com name=tj_trmap class=mnav>地图</a> <a href=http://v.baidu.com name=tj_trvideo class=mnav>视频</a> <a href=http://tieba.baidu.com name=tj_trtieba class=mnav>贴吧</a> <noscript> <a href=http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2f%3fbdorz_come%3d1 name=tj_login class=lb>登录</a> </noscript> <script>document.write('<a href="http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u='+ encodeURIComponent(window.location.href+ (window.location.search === "" ? "?" : "&")+ "bdorz_come=1")+ '" name="tj_login" class="lb">登录</a>');</script> <a href=//www.baidu.com/more/ name=tj_briicon class=bri style="display: block;">更多产品</a> </div> </div> </div> <div id=ftCon> <div id=ftConw> <p id=lh> <a href=http://home.baidu.com>关于百度</a> <a href=http://ir.baidu.com>About Baidu</a> </p> <p id=cp>©2016 Baidu <a href=http://www.baidu.com/duty/>使用百度前必读</a> <a href=http://jianyi.baidu.com/ class=cp-feedback>意见反馈</a> 京ICP证030173号 <img src=//www.baidu.com/img/gs.gif> </p> </div> </div> </div> </body> </html>