转自：https://www.cnblogs.com/codingexperience/p/5319850.html
一、HttpClient简介
HttpClient是一个客户端的HTTP通信实现库，它不是一个浏览器。关于HTTP协议，可以搜索相关的资料。它设计的目的是发送与接收HTTP报文。它不会执行嵌入在页面中JavaScript代码，所以当需要抓取通过AJAX技术获取实际内容的页面时需要使用WebClient等其他开源库。HttpClient最新版已经到第5版，但已经稳定的应该是4.5.2版本，官方网址：http://hc.apache.org/。
二、HttpClient简单使用
HttpClient的主要用途是接收HTTP响应的内容，下面介绍HttpClient的简单使用，抓取博客园的首页。至于HttpClient4.5的常用API可以参考这篇文章：http://liangbizhi.github.io/httpclient-4-3-x-chapter-1/。
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package com.httpclient.demo;import java.io.IOException;import java.nio.charset.Charset;import java.util.regex.Matcher;import java.util.regex.Pattern;import org.apache.http.HttpEntity;import org.apache.http.HttpStatus;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.entity.ContentType;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.util.EntityUtils;public class SimpleHttpClient { // 使用HttpClient获取博客园首页 public static void main(String[] args) throws ClientProtocolException, IOException { String targetUrl = "http://www.cnblogs.com/"; // 1.建立HttpClient对象 CloseableHttpClient client = HttpClients.createDefault(); // 2.建立Get请求 HttpGet get = new HttpGet(targetUrl); // 3.发送Get请求 CloseableHttpResponse res = client.execute(get); // 4.处理请求结果 if (res.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { HttpEntity entity = res.getEntity(); ContentType contentType = ContentType.getOrDefault(entity); Charset charset = contentType.getCharset(); String mimeType = contentType.getMimeType(); // 获取字节数组 byte[] content = EntityUtils.toByteArray(entity); if (charset == null) { // 默认编码转成字符串 String temp = new String(content); String regEx = "(?=<meta).*?(?<=charset=[\'|\"]?)([[a-z]|[A-Z]|[0-9]|-]*)"; Pattern p = Pattern.compile(regEx, Pattern.CASE_INSENSITIVE); Matcher m = p.matcher(temp); if (m.find() && m.groupCount() == 1) { charset = Charset.forName(m.group(1)); } else { charset = Charset.forName("ISO-8859-1"); } } System.out.println(new String(content, charset)); } }} |
三、HttpClient模拟登陆
HTTP协议本来是无状态的，但为了保持会话的状态，使用Cookie保存Session信息，当向服务器发送请求时会附加一些会话信息，从而能区分不同会话的状态。用户登陆过程，其实简单而言，就是首先验证用户名与密码，然后服务器生成会话信息保存到本地，最后用户凭借会话信息能够访问类似用户信息等需登陆的网页。
HttpClient4.5通过CookieStore保存用户的会话信息，还提供HttpClientContext保存用户连接的信息。下面是一个使用HttpClient模拟知乎登陆的简单案例。
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package com.httpclient.demo;import java.io.IOException;import java.util.LinkedList;import java.util.List;import org.apache.http.Consts;import org.apache.http.NameValuePair;import org.apache.http.client.CookieStore;import org.apache.http.client.config.CookieSpecs;import org.apache.http.client.config.RequestConfig;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.client.protocol.HttpClientContext;import org.apache.http.cookie.Cookie;import org.apache.http.impl.client.BasicCookieStore;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;/** * 模拟登陆知乎 */public class ZhiHuTest { public static void main(String[] args) throws java.text.ParseException { String name = "username"; String password = "password" // 全局请求设置 RequestConfig globalConfig = RequestConfig.custom().setCookieSpec(CookieSpecs.STANDARD).build(); // 创建cookie store的本地实例 CookieStore cookieStore = new BasicCookieStore(); // 创建HttpClient上下文 HttpClientContext context = HttpClientContext.create(); context.setCookieStore(cookieStore); // 创建一个HttpClient CloseableHttpClient httpClient = HttpClients.custom().setDefaultRequestConfig(globalConfig) .setDefaultCookieStore(cookieStore).build(); CloseableHttpResponse res = null; // 创建本地的HTTP内容 try { try { // 创建一个get请求用来获取必要的Cookie，如_xsrf信息 HttpGet get = new HttpGet("http://www.zhihu.com/"); res = httpClient.execute(get, context); // 获取常用Cookie,包括_xsrf信息 System.out.println("访问知乎首页后的获取的常规Cookie:==============="); for (Cookie c : cookieStore.getCookies()) { System.out.println(c.getName() + ": " + c.getValue()); } res.close(); // 构造post数据 List<NameValuePair> valuePairs = new LinkedList<NameValuePair>(); valuePairs.add(new BasicNameValuePair("email", name)); valuePairs.add(new BasicNameValuePair("password", password)); valuePairs.add(new BasicNameValuePair("remember_me", "true")); UrlEncodedFormEntity entity = new UrlEncodedFormEntity(valuePairs, Consts.UTF_8); entity.setContentType("application/x-www-form-urlencoded"); // 创建一个post请求 HttpPost post = new HttpPost("https://www.zhihu.com/login/email"); // 注入post数据 post.setEntity(entity); res = httpClient.execute(post, context); // 打印响应信息，查看是否登陆是否成功 System.out.println("打印响应信息==========="); HttpClientUtils.printResponse(res); res.close(); System.out.println("登陆成功后,新的Cookie:==============="); for (Cookie c : context.getCookieStore().getCookies()) { System.out.println(c.getName() + ": " + c.getValue()); } // 构造一个新的get请求，用来测试登录是否成功 HttpGet newGet = new HttpGet("http://www.zhihu.com/question/following"); res = httpClient.execute(newGet, context); String content = EntityUtils.toString(res.getEntity()); System.out.println("登陆成功后访问的页面==============="); System.out.println(content); res.close(); } finally { httpClient.close(); } } catch (IOException e) { e.printStackTrace(); } }} |