HttpClient使用详解
一、简介
HttpClient是Apache Jakarta Common下的子项目，用来提供高效的、最新的、功能丰富的支持HTTP协议的客户端编程工具包，并且它支持HTTP协议最新的版本和建议。 HttpClient已经应用在很多的项目中，比如Apache Jakarta上很著名的另外两个开源项目Cactus和HTMLUnit都使用了HttpClient。
下载地址: http://hc.apache.org/downloads.cgi
二、特性
1. 基于标准、纯净的java语言。实现了Http1.0和Http1.1
2. 以可扩展的面向对象的结构实现了Http全部的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。
3. 支持HTTPS协议。
4. 通过Http代理建立透明的连接。
5. 利用CONNECT方法通过Http代理建立隧道的https连接。
6. Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos认证方案。
7. 插件式的自定义认证方案。
8. 便携可靠的套接字工厂使它更容易的使用第三方解决方案。
9. 连接管理器支持多线程应用。支持设置最大连接数，同时支持设置每个主机的最大连接数，发现并关闭过期的连接。
10. 自动处理Set-Cookie中的Cookie。
11. 插件式的自定义Cookie策略。
12. Request的输出流可以避免流中内容直接缓冲到socket服务器。
13. Response的输入流可以有效的从socket服务器直接读取相应内容。
14. 在http1.0和http1.1中利用KeepAlive保持持久连接。
15. 直接获取服务器发送的response code和 headers。
16. 设置连接超时的能力。
17. 实验性的支持http1.1 response caching。
18. 源代码基于Apache License 可免费获取。
三、使用方法
使用HttpClient发送请求、接收响应很简单，一般需要如下几步即可。
1. 创建HttpClient对象。
2. 创建请求方法的实例，并指定请求URL。如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象。
3. 如果需要发送请求参数，可调用HttpGet、HttpPost共同的 setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数。
4. 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。
5. 调用HttpResponse的getAllHeaders()、 getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器 的响应内容。程序可通过该对象获取服务器的响应内容。
6. 释放连接。无论执行方法是否成功，都必须释放连接
四、实例
package com . test ;import java.io.File ;import java.io.FileInputStream ;import java.io.IOException ;import java.io.UnsupportedEncodingException ;import java.security.KeyManagementException ;import java.security.KeyStore ;import java.security.KeyStoreException ;import java.security.NoSuchAlgorithmException ;import java.security.cert.CertificateException ;import java.util.ArrayList ;import java.util.List ;import javax.net.ssl.SSLContext ;import org.apache.http.HttpEntity ;import org.apache.http.NameValuePair ;import org.apache.http.ParseException ;import org.apache.http.client.ClientProtocolException ;import org.apache.http.client.entity.UrlEncodedFormEntity ;import org.apache.http.client.methods.CloseableHttpResponse ;import org.apache.http.client.methods.HttpGet ;import org.apache.http.client.methods.HttpPost ;import org.apache.http.conn.ssl.SSLConnectionSocketFactory ;import org.apache.http.conn.ssl.SSLContexts ;import org.apache.http.conn.ssl.TrustSelfSignedStrategy ;import org.apache.http.entity.ContentType ;import org.apache.http.entity.mime.MultipartEntityBuilder ;import org.apache.http.entity.mime.content.FileBody ;import org.apache.http.entity.mime.content.StringBody ;import org.apache.http.impl.client.CloseableHttpClient ;import org.apache.http.impl.client.HttpClients ;import org.apache.http.message.BasicNameValuePair ;import org.apache.http.util.EntityUtils ;import org.junit.Test ;public class HttpClientTest {@Testpublic void jUnitTest () {get ();}/*** HttpClient连接SSL*/public void ssl () {CloseableHttpClient httpclient = null ;try {KeyStore trustStore = KeyStore . getInstance ( KeyStore . getDefaultType ());FileInputStream instream = new FileInputStream ( new File ( "d:\\tomcat.keystore" ));try {// 加载keyStore d:\\tomcat.keystoretrustStore . load ( instream , "123456" . toCharArray ());} catch ( CertificateException e ) {e . printStackTrace ();} finally {try {instream . close ();} catch ( Exception ignore ) {}}// 相信自己的CA和所有自签名的证书SSLContext sslcontext = SSLContexts . custom (). loadTrustMaterial ( trustStore , new TrustSelfSignedStrategy ()). build ();// 只允许使用TLSv1协议SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory ( sslcontext , new String [] { "TLSv1" }, null ,SSLConnectionSocketFactory . BROWSER_COMPATIBLE_HOSTNAME_VERIFIER );httpclient = HttpClients . custom (). setSSLSocketFactory ( sslsf ). build ();// 创建http请求(get方式)HttpGet httpget = new HttpGet ( "https://localhost:8443/myDemo/Ajax/serivceJ.action" );System . out . println ( "executing request" + httpget . getRequestLine ());CloseableHttpResponse response = httpclient . execute ( httpget );try {HttpEntity entity = response . getEntity ();System . out . println ( "----------------------------------------" );System . out . println ( response . getStatusLine ());if ( entity != null ) {System . out . println ( "Response content length: " + entity . getContentLength ());System . out . println ( EntityUtils . toString ( entity ));EntityUtils . consume ( entity );}} finally {response . close ();}} catch ( ParseException e ) {e . printStackTrace ();} catch ( IOException e ) {e . printStackTrace ();} catch ( KeyManagementException e ) {e . printStackTrace ();} catch ( NoSuchAlgorithmException e ) {e . printStackTrace ();} catch ( KeyStoreException e ) {e . printStackTrace ();} finally {if ( httpclient != null ) {try {httpclient . close ();} catch ( IOException e ) {e . printStackTrace ();}}}}/*** post方式提交表单（模拟用户登录请求）*/public void postForm () {// 创建默认的httpClient实例.CloseableHttpClient httpclient = HttpClients . createDefault ();// 创建httppostHttpPost httppost = new HttpPost ( "http://localhost:8080/myDemo/Ajax/serivceJ.action" );// 创建参数队列List < namevaluepair > formparams = new ArrayList < namevaluepair >();formparams . add ( new BasicNameValuePair ( "username" , "admin" ));formparams . add ( new BasicNameValuePair ( "password" , "123456" ));UrlEncodedFormEntity uefEntity ;try {uefEntity = new UrlEncodedFormEntity ( formparams , "UTF-8" );httppost . setEntity ( uefEntity );System . out . println ( "executing request " + httppost . getURI ());CloseableHttpResponse response = httpclient . execute ( httppost );try {HttpEntity entity = response . getEntity ();if ( entity != null ) {System . out . println ( "--------------------------------------" );System . out . println ( "Response content: " + EntityUtils . toString ( entity , "UTF-8" ));System . out . println ( "--------------------------------------" );}} finally {response . close ();}} catch ( ClientProtocolException e ) {e . printStackTrace ();} catch ( UnsupportedEncodingException e1 ) {e1 . printStackTrace ();} catch ( IOException e ) {e . printStackTrace ();} finally {// 关闭连接,释放资源try {httpclient . close ();} catch ( IOException e ) {e . printStackTrace ();}}}/*** 发送 post请求访问本地应用并根据传递参数不同返回不同结果*/public void post () {// 创建默认的httpClient实例.CloseableHttpClient httpclient = HttpClients . createDefault ();// 创建httppostHttpPost httppost = new HttpPost ( "http://localhost:8080/myDemo/Ajax/serivceJ.action" );// 创建参数队列List < namevaluepair > formparams = new ArrayList < namevaluepair >();formparams . add ( new BasicNameValuePair ( "type" , "house" ));UrlEncodedFormEntity uefEntity ;try {uefEntity = new UrlEncodedFormEntity ( formparams , "UTF-8" );httppost . setEntity ( uefEntity );System . out . println ( "executing request " + httppost . getURI ());CloseableHttpResponse response = httpclient . execute ( httppost );try {HttpEntity entity = response . getEntity ();if ( entity != null ) {System . out . println ( "--------------------------------------" );System . out . println ( "Response content: " + EntityUtils . toString ( entity , "UTF-8" ));System . out . println ( "--------------------------------------" );}} finally {response . close ();}} catch ( ClientProtocolException e ) {e . printStackTrace ();} catch ( UnsupportedEncodingException e1 ) {e1 . printStackTrace ();} catch ( IOException e ) {e . printStackTrace ();} finally {// 关闭连接,释放资源try {httpclient . close ();} catch ( IOException e ) {e . printStackTrace ();}}}/*** 发送 get请求*/public void get () {CloseableHttpClient httpclient = HttpClients . createDefault ();try {// 创建httpget.HttpGet httpget = new HttpGet ( "http://www.baidu.com/" );System . out . println ( "executing request " + httpget . getURI ());// 执行get请求.CloseableHttpResponse response = httpclient . execute ( httpget );try {// 获取响应实体HttpEntity entity = response . getEntity ();System . out . println ( "--------------------------------------" );// 打印响应状态System . out . println ( response . getStatusLine ());if ( entity != null ) {// 打印响应内容长度System . out . println ( "Response content length: " + entity . getContentLength ());// 打印响应内容System . out . println ( "Response content: " + EntityUtils . toString ( entity ));}System . out . println ( "------------------------------------" );} finally {response . close ();}} catch ( ClientProtocolException e ) {e . printStackTrace ();} catch ( ParseException e ) {e . printStackTrace ();} catch ( IOException e ) {e . printStackTrace ();} finally {// 关闭连接,释放资源try {httpclient . close ();} catch ( IOException e ) {e . printStackTrace ();}}}/*** 上传文件*/public void upload () {CloseableHttpClient httpclient = HttpClients . createDefault ();try {HttpPost httppost = new HttpPost ( "http://localhost:8080/myDemo/Ajax/serivceFile.action" );FileBody bin = new FileBody ( new File ( "F:\\image\\sendpix0.jpg" ));StringBody comment = new StringBody ( "A binary file of some kind" , ContentType . TEXT_PLAIN );HttpEntity reqEntity = MultipartEntityBuilder . create (). addPart ( "bin" , bin ). addPart ( "comment" , comment ). build ();httppost . setEntity ( reqEntity );System . out . println ( "executing request " + httppost . getRequestLine ());CloseableHttpResponse response = httpclient . execute ( httppost );try {System . out . println ( "----------------------------------------" );System . out . println ( response . getStatusLine ());HttpEntity resEntity = response . getEntity ();if ( resEntity != null ) {System . out . println ( "Response content length: " + resEntity . getContentLength ());}EntityUtils . consume ( resEntity );} finally {response . close ();}} catch ( ClientProtocolException e ) {e . printStackTrace ();} catch ( IOException e ) {e . printStackTrace ();} finally {try {httpclient . close ();} catch ( IOException e ) {e . printStackTrace ();}}}}</ namevaluepair ></ namevaluepair ></ namevaluepair ></ namevaluepair >