Java：HttpClient篇，HttpClient4.2在Java中的几则应用：Get、Post参数、Session（会话）保持、Proxy（代理服务器）设置，多线程设置......

原文：http://www.cnblogs.com/nayitian/p/3282029.html

新版HttpClient4.2与之前的3.x版本有了很大变化，建议从http://hc.apache.org/处以得到最新的信息。

关于HttpCore与HttpClient：HttpCore是位于HTTP传输组件的底层包，可以用来简化HTTP客户端与服务器端的开发。HttpClient是一个符合HTTP1.1版本，基于HttpCore类包的一个实现。它同时为客户端认证、HTTP状态管理、HTTP连接管理提供了可重用的客户端组件。HttpCore类包目前最新发布版本是httpcore-4.2.4；HttpClient类包的版本是httpclient-4.2.5。
了解到HttpCore包与HttpClient包的差别，在程序中就应该大致知道一些包它们存在于哪个类库中。比如：org.apache.http包属于HttpCore，而org.apache.http.client包属于HttpClient。
HttpClient的API文档在下载的zip中已经包括；
HttpCore的API文档可以参考：http://hc.apache.org/httpcomponents-core-4.2.x/httpcore/apidocs/index.html
HttpClient4.2需要Java 5.0及以上版本；需要支持包有（下载zip包中已经包括）：
* Apache HttpComponents HttpCore
* Apache Commons Logging
* Apache Commons Codec

1. 获取一个HTML页面的内容，一个简单的get应用

    // 获取一个HTML页面的内容，一个简单的get应用public void grabPageHTML() throws Exception {HttpClient httpclient = new DefaultHttpClient();HttpGet httpget = new HttpGet("http://www.baidu.com/");HttpResponse response = httpclient.execute(httpget);HttpEntity entity = response.getEntity();String html = EntityUtils.toString(entity, "GBK");// releaseConnection等同于reset，作用是重置request状态位，为下次使用做好准备。// 其实就是用一个HttpGet获取多个页面的情况下有效果；否则可以忽略此方法。httpget.releaseConnection();System.out.println(html);}

2. 下载一个文件到本地（本示范中为一个验证码图片）

    // 下载一个文件到本地（本示范中为一个验证码图片）public void downloadFile() throws Exception {String url = "http://www.lashou.com/account/captcha";String destfilename = "D:\\TDDOWNLOAD\\yz.png";HttpClient httpclient = new DefaultHttpClient();HttpGet httpget = new HttpGet(url);File file = new File(destfilename);if (file.exists()) {file.delete();}HttpResponse response = httpclient.execute(httpget);HttpEntity entity = response.getEntity();InputStream in = entity.getContent();try {FileOutputStream fout = new FileOutputStream(file);int l = -1;byte[] tmp = new byte[2048]; while ((l = in.read(tmp)) != -1) {fout.write(tmp);} fout.close();} finally {// 在用InputStream处理HttpEntity时，切记要关闭低层流。in.close();}httpget.releaseConnection();}

3. Post方法，模拟表单提交参数登录到网站并打开会员页面获取内容（会话保持）

    // Post方法，模拟表单提交参数登录到网站。// 结合了上面两个方法：grabPageHTML/downloadFile，同时增加了Post的代码。public void login2Lashou() throws Exception {// 第一步：先下载验证码到本地String url = "http://www.lashou.com/account/captcha";String destfilename = "D:\\TDDOWNLOAD\\yz.png";HttpClient httpclient = new DefaultHttpClient();HttpGet httpget = new HttpGet(url);File file = new File(destfilename);if (file.exists()) {file.delete();}HttpResponse response = httpclient.execute(httpget);HttpEntity entity = response.getEntity();InputStream in = entity.getContent();try {FileOutputStream fout = new FileOutputStream(file);int l = -1;byte[] tmp = new byte[2048]; while ((l = in.read(tmp)) != -1) {fout.write(tmp);} fout.close();} finally {in.close();}httpget.releaseConnection();
        // 第二步：用Post方法带若干参数尝试登录，需要手工输入下载验证码中显示的字母、数字BufferedReader br = new BufferedReader(new InputStreamReader(System.in));System.out.println("请输入下载下来的验证码中显示的数字...");String yan = br.readLine();HttpPost httppost = new HttpPost("http://www.lashou.com/account/login/");List<NameValuePair> params = new ArrayList<NameValuePair>();params.add(new BasicNameValuePair("user_id", "testuser007"));params.add(new BasicNameValuePair("pwd", "asdfg123"));params.add(new BasicNameValuePair("yan", yan));params.add(new BasicNameValuePair("save_user", "on"));params.add(new BasicNameValuePair("save_pwd", "on"));params.add(new BasicNameValuePair("sub", "登录"));httppost.setEntity(new UrlEncodedFormEntity(params));response = httpclient.execute(httppost);entity = response.getEntity();// 在这里可以用Jsoup之类的工具对返回结果进行分析，以判断登录是否成功String postResult = EntityUtils.toString(entity, "GBK"); // 我们这里只是简单的打印出当前Cookie值以判断登录是否成功。List<Cookie> cookies = ((AbstractHttpClient)httpclient).getCookieStore().getCookies();for(Cookie cookie: cookies)System.out.println(cookie);httppost.releaseConnection();
        // 第三步：打开会员页面以判断登录成功（未登录用户是打不开会员页面的）String memberpage = "http://www.lashou.com/account/orders/";httpget = new HttpGet(memberpage);response = httpclient.execute(httpget); // 必须是同一个HttpClient！entity = response.getEntity();String html = EntityUtils.toString(entity, "GBK");httpget.releaseConnection();System.out.println(html);}

输出：

请输入下载下来的验证码中显示的数字...
sbzq
...

[version: 0][name: login_name2][value: testuser007][domain: www.lashou.com][path: /][expiry: Mon Sep 09 10:21:19 CST 2013]
[version: 0][name: pwd2][value: 4c88a4062736c26572d3ec382868fa2b][domain: lashou.com][path: /][expiry: Mon Sep 09 10:21:19 CST 2013]
?<!doctype html>

...

4. 设置代理服务器

    // 设置代理服务器public void testProxy() throws Exception {HttpHost proxy = new HttpHost("127.0.0.1", 8888);// 方式一HttpClient httpclient = new DefaultHttpClient();httpclient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY, proxy);// 方式二HttpParams params = new BasicHttpParams(); params.setParameter(ConnRoutePNames.DEFAULT_PROXY, proxy);HttpClient httpclient1 = new DefaultHttpClient(params);}

5. 几种常用HTTP头的设置

    // 几种常用HTTP头的设置public void testBasicHeader() throws Exception {HttpParams params = new BasicHttpParams(); Collection<BasicHeader> collection = new ArrayList<BasicHeader>();collection.add(new BasicHeader("Accept", "text/html, application/xhtml+xml, */*"));collection.add(new BasicHeader("Referer", "http://www.sina.com/"));collection.add(new BasicHeader("Accept-Language", "zh-CN"));collection.add(new BasicHeader("User-Agent", "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)"));collection.add(new BasicHeader("Accept-Encoding", "gzip, deflate"));params.setParameter(ClientPNames.DEFAULT_HEADERS, collection);HttpClient httpclient = new DefaultHttpClient(params);// 下面内容略}

6. 多线程编程下的线程池设置

    // 多线程编程下的线程池设置（这点在需要登录且用一个HttpClient对象抓取多个页面的情况下特别有用）public void testConnectionManager() throws Exception {// 连接池设置SchemeRegistry schemeRegistry = new SchemeRegistry();schemeRegistry.register(new Scheme("http", 80, PlainSocketFactory.getSocketFactory()));schemeRegistry.register(new Scheme("https", 443, SSLSocketFactory.getSocketFactory()));PoolingClientConnectionManager cm = new PoolingClientConnectionManager(schemeRegistry);cm.setMaxTotal(200); // 连接池里的最大连接数cm.setDefaultMaxPerRoute(20); // 每个路由的默认最大连接数HttpHost localhost = new HttpHost("locahost", 80); // 可以针对某特定网站指定最大连接数cm.setMaxPerRoute(new HttpRoute(localhost), 30);// 其它设置HttpParams params = new BasicHttpParams(); params.setParameter(ClientPNames.COOKIE_POLICY, CookiePolicy.BROWSER_COMPATIBILITY);HttpClient httpclient = new DefaultHttpClient(cm, params);// 下面内容略}

7. 测试HTTP上下文对象（HttpContext）

    // 测试HTTP上下文对象（HttpContext）public void testContext() throws Exception {// 请求一个页面，然后解析各上下文对象DefaultHttpClient httpclient = new DefaultHttpClient();HttpContext localContext = new BasicHttpContext();HttpGet httpget = new HttpGet("http://www.baidu.com/");HttpResponse response = httpclient.execute(httpget, localContext);// the actual connection to the target server.HttpConnection conn = (HttpConnection) localContext.getAttribute(ExecutionContext.HTTP_CONNECTION);  System.out.println("Socket timeout: " + conn.getSocketTimeout());  // the connection targetHttpHost target = (HttpHost) localContext.getAttribute(ExecutionContext.HTTP_TARGET_HOST);System.out.println("Final target: " + target);// the connection proxy, if used HttpHost proxy = (HttpHost) localContext.getAttribute(ExecutionContext.HTTP_PROXY_HOST);if (proxy != null)System.out.println("Proxy host/port: " + proxy.getHostName() + "/"+ proxy.getPort());// the actual HTTP requestHttpRequest request = (HttpRequest) localContext.getAttribute(ExecutionContext.HTTP_REQUEST);System.out.println("HTTP version: " + request.getProtocolVersion());Header[] headers = request.getAllHeaders();System.out.println("HTTP Headers: ");for (Header header : headers) {System.out.println("\t" + header.getName() + ": " + header.getValue());}System.out.println("HTTP URI: " + request.getRequestLine().getUri());// the actual HTTP responseresponse = (HttpResponse) localContext.getAttribute(ExecutionContext.HTTP_RESPONSE);HttpEntity entity = response.getEntity();if (entity != null) {System.out.println("Content Encoding：" + entity.getContentEncoding());System.out.println("Content Type：" + entity.getContentType());}// the flag indicating whether the actual request has been fully transmitted to the connection target. System.out.println("Sent flag: " + localContext.getAttribute(ExecutionContext.HTTP_REQ_SENT));
        // 如果没有用到返回entity中的内容，那么要把它消费掉，以保证底层的资源得以释放。entity = response.getEntity();EntityUtils.consume(entity);}

输出：

Socket timeout: 0
Final target: http://www.baidu.com
HTTP version: HTTP/1.1
HTTP Headers:
    Host: www.baidu.com
    Connection: Keep-Alive
    User-Agent: Apache-HttpClient/4.2.5 (java 1.5)
HTTP URI: /
Content Encoding：null
Content Type：Content-Type: text/html;charset=utf-8
Sent flag: true

8. 完整的代码

package com.clzhang.sample.net;import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;import org.apache.http.Header;
import org.apache.http.HttpConnection;
import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.params.ClientPNames;
import org.apache.http.client.params.CookiePolicy;
import org.apache.http.conn.params.ConnRoutePNames;
import org.apache.http.conn.routing.HttpRoute;
import org.apache.http.conn.scheme.PlainSocketFactory;
import org.apache.http.conn.scheme.Scheme;
import org.apache.http.conn.scheme.SchemeRegistry;
import org.apache.http.conn.ssl.SSLSocketFactory;
import org.apache.http.cookie.Cookie;
import org.apache.http.impl.client.AbstractHttpClient;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.PoolingClientConnectionManager;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpParams;
import org.apache.http.protocol.BasicHttpContext;
import org.apache.http.protocol.ExecutionContext;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.EntityUtils;public class HttpClientSample1 {// 获取一个HTML页面的内容，一个简单的get应用public void grabPageHTML() throws Exception {HttpClient httpclient = new DefaultHttpClient();HttpGet httpget = new HttpGet("http://www.baidu.com/");HttpResponse response = httpclient.execute(httpget);HttpEntity entity = response.getEntity();String html = EntityUtils.toString(entity, "GBK");// releaseConnection等同于reset，作用是重置request状态位，为下次使用做好准备。// 其实就是用一个HttpGet获取多个页面的情况下有效果；否则可以忽略此方法。httpget.releaseConnection();System.out.println(html);}// 下载一个文件到本地（本示范中为一个验证码图片）public void downloadFile() throws Exception {String url = "http://www.lashou.com/account/captcha";String destfilename = "D:\\TDDOWNLOAD\\yz.png";HttpClient httpclient = new DefaultHttpClient();HttpGet httpget = new HttpGet(url);File file = new File(destfilename);if (file.exists()) {file.delete();}HttpResponse response = httpclient.execute(httpget);HttpEntity entity = response.getEntity();InputStream in = entity.getContent();try {FileOutputStream fout = new FileOutputStream(file);int l = -1;byte[] tmp = new byte[2048]; while ((l = in.read(tmp)) != -1) {fout.write(tmp);} fout.close();} finally {// 在用InputStream处理HttpEntity时，切记要关闭低层流。in.close();}httpget.releaseConnection();}// Post方法，模拟表单提交参数登录到网站。// 结合了上面两个方法：grabPageHTML/downloadFile，同时增加了Post的代码。public void login2Lashou() throws Exception {// 第一步：先下载验证码到本地String url = "http://www.lashou.com/account/captcha";String destfilename = "D:\\TDDOWNLOAD\\yz.png";HttpClient httpclient = new DefaultHttpClient();HttpGet httpget = new HttpGet(url);File file = new File(destfilename);if (file.exists()) {file.delete();}HttpResponse response = httpclient.execute(httpget);HttpEntity entity = response.getEntity();InputStream in = entity.getContent();try {FileOutputStream fout = new FileOutputStream(file);int l = -1;byte[] tmp = new byte[2048]; while ((l = in.read(tmp)) != -1) {fout.write(tmp);} fout.close();} finally {in.close();}httpget.releaseConnection();// 第二步：用Post方法带若干参数尝试登录，需要手工输入下载验证码中显示的字母、数字BufferedReader br = new BufferedReader(new InputStreamReader(System.in));System.out.println("请输入下载下来的验证码中显示的数字...");String yan = br.readLine();HttpPost httppost = new HttpPost("http://www.lashou.com/account/login/");List<NameValuePair> params = new ArrayList<NameValuePair>();params.add(new BasicNameValuePair("user_id", "testuser007"));params.add(new BasicNameValuePair("pwd", "asdfg123"));params.add(new BasicNameValuePair("yan", yan));params.add(new BasicNameValuePair("save_user", "on"));params.add(new BasicNameValuePair("save_pwd", "on"));params.add(new BasicNameValuePair("sub", "登录"));httppost.setEntity(new UrlEncodedFormEntity(params));response = httpclient.execute(httppost);entity = response.getEntity();// 在这里可以用Jsoup之类的工具对返回结果进行分析，以判断登录是否成功String postResult = EntityUtils.toString(entity, "GBK"); // 我们这里只是简单的打印出当前Cookie值以判断登录是否成功。List<Cookie> cookies = ((AbstractHttpClient)httpclient).getCookieStore().getCookies();for(Cookie cookie: cookies)System.out.println(cookie);httppost.releaseConnection();// 第三步：打开会员页面以判断登录成功（未登录用户是打不开会员页面的）String memberpage = "http://www.lashou.com/account/orders/";httpget = new HttpGet(memberpage);response = httpclient.execute(httpget); // 必须是同一个HttpClient！entity = response.getEntity();String html = EntityUtils.toString(entity, "GBK");httpget.releaseConnection();System.out.println(html);}// 设置代理服务器public void testProxy() throws Exception {HttpHost proxy = new HttpHost("127.0.0.1", 8888);// 方式一HttpClient httpclient = new DefaultHttpClient();httpclient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY, proxy);// 方式二HttpParams params = new BasicHttpParams(); params.setParameter(ConnRoutePNames.DEFAULT_PROXY, proxy);HttpClient httpclient1 = new DefaultHttpClient(params);}// 几种常用HTTP头的设置public void testBasicHeader() throws Exception {HttpParams params = new BasicHttpParams(); Collection<BasicHeader> collection = new ArrayList<BasicHeader>();collection.add(new BasicHeader("Accept", "text/html, application/xhtml+xml, */*"));collection.add(new BasicHeader("Referer", "http://www.sina.com/"));collection.add(new BasicHeader("Accept-Language", "zh-CN"));collection.add(new BasicHeader("User-Agent", "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)"));collection.add(new BasicHeader("Accept-Encoding", "gzip, deflate"));params.setParameter(ClientPNames.DEFAULT_HEADERS, collection);HttpClient httpclient = new DefaultHttpClient(params);// 下面内容略}// 多线程编程下的线程池设置（这点在需要登录且用一个HttpClient对象抓取多个页面的情况下特别有用）public void testConnectionManager() throws Exception {// 连接池设置SchemeRegistry schemeRegistry = new SchemeRegistry();schemeRegistry.register(new Scheme("http", 80, PlainSocketFactory.getSocketFactory()));schemeRegistry.register(new Scheme("https", 443, SSLSocketFactory.getSocketFactory()));PoolingClientConnectionManager cm = new PoolingClientConnectionManager(schemeRegistry);cm.setMaxTotal(200); // 连接池里的最大连接数cm.setDefaultMaxPerRoute(20); // 每个路由的默认最大连接数HttpHost localhost = new HttpHost("locahost", 80); // 可以针对某特定网站指定最大连接数cm.setMaxPerRoute(new HttpRoute(localhost), 30);// 其它设置HttpParams params = new BasicHttpParams(); params.setParameter(ClientPNames.COOKIE_POLICY, CookiePolicy.BROWSER_COMPATIBILITY);HttpClient httpclient = new DefaultHttpClient(cm, params);// 下面内容略}// 测试HTTP上下文对象（HttpContext）public void testContext() throws Exception {// 请求一个页面，然后解析各上下文对象DefaultHttpClient httpclient = new DefaultHttpClient();HttpContext localContext = new BasicHttpContext();HttpGet httpget = new HttpGet("http://www.baidu.com/");HttpResponse response = httpclient.execute(httpget, localContext);// the actual connection to the target server.HttpConnection conn = (HttpConnection) localContext.getAttribute(ExecutionContext.HTTP_CONNECTION);  System.out.println("Socket timeout: " + conn.getSocketTimeout());  // the connection targetHttpHost target = (HttpHost) localContext.getAttribute(ExecutionContext.HTTP_TARGET_HOST);System.out.println("Final target: " + target);// the connection proxy, if used HttpHost proxy = (HttpHost) localContext.getAttribute(ExecutionContext.HTTP_PROXY_HOST);if (proxy != null)System.out.println("Proxy host/port: " + proxy.getHostName() + "/"+ proxy.getPort());// the actual HTTP requestHttpRequest request = (HttpRequest) localContext.getAttribute(ExecutionContext.HTTP_REQUEST);System.out.println("HTTP version: " + request.getProtocolVersion());Header[] headers = request.getAllHeaders();System.out.println("HTTP Headers: ");for (Header header : headers) {System.out.println("\t" + header.getName() + ": " + header.getValue());}System.out.println("HTTP URI: " + request.getRequestLine().getUri());// the actual HTTP responseresponse = (HttpResponse) localContext.getAttribute(ExecutionContext.HTTP_RESPONSE);HttpEntity entity = response.getEntity();if (entity != null) {System.out.println("Content Encoding：" + entity.getContentEncoding());System.out.println("Content Type：" + entity.getContentType());}// the flag indicating whether the actual request has been fully transmitted to the connection target. System.out.println("Sent flag: " + localContext.getAttribute(ExecutionContext.HTTP_REQ_SENT));// 如果没有用到返回entity中的内容，那么要把它消费掉，以保证底层的资源得以释放。entity = response.getEntity();EntityUtils.consume(entity);}    public static void main(String[] args) throws Exception {HttpClientSample1 ins = new HttpClientSample1();//        ins.grabPageHTML();
//        ins.downloadFile();ins.login2Lashou();
//        ins.testContext();}
}

转载于:https://www.cnblogs.com/shihaiming/p/7657012.html