HttpComponents是Apache 旗下的项目。其中有一个HttpClient，即HTTP客户端。
之后我们建立项目，导入jar包，开始开发
一、获取网页内容:
package com.zhi.httpClient; import java.io.IOException; import org.apache.http.HttpEntity;import org.apache.http.ParseException;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.util.EntityUtils; public class Demo { ???public static void main(String[] args) { ???????CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、创建实例 ???????//CloseableHttpClient意思是：可关闭的 ???????HttpGet httpGet=new HttpGet("http://www.huimsoft.com"); //2、创建实例 ????????????????//限制类型http://www.tuicool.com/ ????????????????CloseableHttpResponse closeableHttpResponse=null; ???????try { ???????????closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、执行 ???????} catch (ClientProtocolException e) { //客户端协议异常 ???????????// TODO Auto-generated catch block ???????????e.printStackTrace(); ???????} catch (IOException e) { //IO异常 ???????????// TODO Auto-generated catch block ???????????e.printStackTrace(); ???????} ???????HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、获取实体 ????????String str=""; ???????try { ???????????str=EntityUtils.toString(httpEntity, "utf-8"); //获取网页内容，并且指定编码 ???????} catch (ParseException e) { //解析异常 ???????????// TODO Auto-generated catch block ???????????e.printStackTrace(); ???????} catch (IOException e) { ???????????// TODO Auto-generated catch block ???????????e.printStackTrace(); ???????} ???????System.out.println(str); ????????????????//关闭closeableHttpResponse ???????try { ???????????closeableHttpResponse.close(); ???????} catch (IOException e) { ???????????// TODO Auto-generated catch block ???????????e.printStackTrace(); ???????} ????????????????//关闭closeableHttpClient ???????try { ???????????closeableHttpClient.close(); ???????} catch (IOException e) { ???????????// TODO Auto-generated catch block ???????????e.printStackTrace(); ???????} ???}}代码有很多，但是很多是在处理异常，所以我们也可以使用throws在方法上抛出，以简化代码格式，让其更好看。
package com.zhi.httpClient; import org.apache.http.HttpEntity;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.util.EntityUtils; public class Test { ???public static void main(String[] args) throws Exception { ???????CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、创建实例 ???????HttpGet httpGet=new HttpGet("http://www.huimsoft.com"); //2、创建请求 ????????????????CloseableHttpResponse closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、执行 ???????HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、获取实体 ???????System.out.println(EntityUtils.toString(httpEntity, "utf-8")); //5、获取网页内容，并且指定编码 ????????????????closeableHttpResponse.close(); ???????closeableHttpClient.close(); ???}}二、设置请求头信息
设置请求头信息的目的是为了模拟浏览器
package com.zhi.httpClient2; import org.apache.http.HttpEntity;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.util.EntityUtils; public class Demo { ????public static void main(String[] args) throws Exception { ???????CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、创建实例 ???????HttpGet httpGet=new HttpGet("http://www.tuicool.com"); //2、创建请求 ????????????????httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36 SE 2.X MetaSr 1.0"); ????????????????CloseableHttpResponse closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、执行 ???????HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、获取实体 ???????System.out.println(EntityUtils.toString(httpEntity, "utf-8")); //5、获取网页内容，并且指定编码 ????????????????closeableHttpResponse.close(); ???????closeableHttpClient.close(); ???} }三、获取相应头信息Response Headers的内容类型Content-type
package com.zhi.httpClient2; import org.apache.http.Header;import org.apache.http.HttpEntity;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients; public class Demo { ???public static void main(String[] args) throws Exception { ???????CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、创建实例 ???????HttpGet httpGet=new HttpGet("http://www.tuicool.com"); //2、创建请求 ????????????????httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36 SE 2.X MetaSr 1.0"); ????????????????CloseableHttpResponse closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、执行 ???????HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、获取实体 ????????????????Header header=httpEntity.getContentType(); ???????System.out.println(header.toString()); //获取头信息内容 ???????System.out.println(header.getName().toString()); //这是获取key ???????System.out.println(header.getValue().toString()); //这是获取value ????????????????//System.out.println(EntityUtils.toString(httpEntity, "utf-8")); //5、获取网页内容，并且指定编码 ???????closeableHttpResponse.close(); ???????closeableHttpClient.close(); ???}}运行输出：
Content-Type: text/html; charset=utf-8
Content-Type
text/html; charset=utf-8
我们的重点是获取的value的值，有些是text/html的，有些是其他的，比如我们请求一个js文件。
https://cdn.bootcss.com/jquery/1.12.4/jquery.min.js
HttpGet httpGet=new HttpGet("http://cdn.bootcss.com/jquery/1.12.4/jquery.min.js");public class Demo { ???public static void main(String[] args) throws Exception { ???????CloseableHttpClient closeableHttpClient=HttpClients.createDefault(); //1、创建实例 ???????HttpGet httpGet=new HttpGet("http://cdn.bootcss.com/jquery/1.12.4/jquery.min.js"); //2、创建实例 ????????????????httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36 SE 2.X MetaSr 1.0"); ????????????????CloseableHttpResponse closeableHttpResponse=closeableHttpClient.execute(httpGet); //3、执行 ???????HttpEntity httpEntity=closeableHttpResponse.getEntity(); //4、获取实体 ????????????????Header header=httpEntity.getContentType(); ???????System.out.println(header.getValue().toString()); //这是获取value ????????????????closeableHttpResponse.close(); ???????closeableHttpClient.close(); ???}}运行结果：
运行结果：application/javascript
如果请求一个图片，同上
运行结果：image/png
HttpClient配置及运用（一）
原文地址：http://www.cnblogs.com/FrankLiner/p/7718699.html