HttpClient使用详解

【本文非博主原创，原文链接：http://blog.csdn.net/wangpeng047/article/details/19624529/】

1.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。

2.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。

3.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

4.示例：

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 {        @Test      public 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.keystore                    trustStore.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httppost            HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");          // 创建参数队列            List formparams = new ArrayList();          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httppost            HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");          // 创建参数队列            List formparams = new ArrayList();          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();              }          }      }  }