HttpClient+Jericho HTML Parser 实现网页的抓取

//转自：chenqi19831112/archive/2008/11/07/3248863.aspx

Jericho HTML Parser是一个简单而功能强大的Java HTML解析器库，可以分析和处理HTML文档的一部分，包括一些通用的服务器端标签，同时也可以重新生成无法识别的或无效的HTML。它也提供了一个有用的HTML表单分析器。
  下载地址:[url]http://sourceforge.net/project/showfiles.php?group_id=101067[/url]

  HttpClient作为HTTP客户端组件与服务器进行通讯，同时使用了jdom进行XML数据的解析。

    * HttpClient 可以在[url]http://jakarta.apache.org/commons/httpclient/downloads.html[/url]下载
    * HttpClient 用到了 Apache Jakarta common 下的子项目 logging，你可以从这个地址[url]http://jakarta.apache.org/site/downloads[/url] /downloads_commons-logging.cgi下载到 common logging，从下载后的压缩包中取出 commons-logging.jar 加到 CLASSPATH 中
    * HttpClient 用到了 Apache Jakarta common 下的子项目 codec，你可以从这个地址[url]http://jakarta.apache.org/site/downloads[/url] /downloads_commons-codec.cgi 下载到最新的 common codec，从下载后的压缩包中取出 commons-codec-1.x.jar 加到 CLASSPATH 中


在对网页信息进行抓取时,主要会用到GET 方法

使用 HttpClient 需要以下 6 个步骤：

1. 创建 HttpClient 的实例

2. 创建某种连接方法的实例，在这里是 GetMethod。在 GetMethod 的构造函数中传入待连接的地址

3. 调用第一步中创建好的实例的 execute 方法来执行第二步中创建好的 method 实例

4. 读 response

5. 释放连接。无论执行方法是否成功，都必须释放连接

6. 对得到后的内容进行处理
在eclipse下建立工程 -->snatch
将上面下载的四个jar文件导入到项目路径中.
环境搭建完成

现在,首先介绍一下HttpClient的使用
在工程目录下创建test包,在包中创建Httpclient Test类

package test;
import java.io.IOException;
import org.apache.commons.httpclient.*;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;
public class HttpClientTest...{
     public static void main(String[] args) {
     //构造HttpClient的实例
    HttpClient httpClient = new HttpClient();
     //创建GET方法的实例
    GetMethod getMethod = new GetMethod( "http://www.google.com.cn");
    //使用系统提供的默认的恢复策略
    getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER,
        new DefaultHttpMethodRetryHandler());
    try {
     //执行getMethod
     int statusCode = httpClient.executeMethod(getMethod);
     if (statusCode != HttpStatus.SC_OK) {
        System.err.println("Method failed: "
            + getMethod.getStatusLine());
     }
     //读取内容
     byte[] responseBody = getMethod.getResponseBoy();
     //处理内容
     System.out.println(new String(responseBody));
    } catch (HttpException e) {
     //发生致命的异常，可能是协议不对或者返回的内容有问题
     System.out.println("Please check your provided http address!");
     e.printStackTrace();
    } catch (IOException e) {
     //发生网络异常
     e.printStackTrace();
    } finally {
     //释放连接
     getMethod.releaseConnection();
    }
}
}

这样得到的是页面的源代码.
这里 byte[] responseBody = getMethod.getResponseBoy();是读取内容
除此之外,我们还可以这样读取:
InputStream inputStream=   getMethod.getResponseBodyAsStream();
String responseBody = getMethod.getResponseBodyAsString();


下面结合两者给个事例
取出[url]http://www.ahcourt.gov.cn/gb/ahgy_2004/fyxw/index.html[/url]
中"信息快递"栏的前几条信息.
新建类CourtNews

package test;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.httpclient.DefaultHttpMethodRetryHandler;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpException;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;

import au.id.jericho.lib.html.Element;
import au.id.jericho.lib.html.HTMLElementName;
import au.id.jericho.lib.html.Segment;
import au.id.jericho.lib.html.Source;

/** *//**
* @author oscar 07-5-17
*
*/
public class CourtNews {
         private int newsCount = 3;

         private List newsList = new ArrayList();

         public int getNewsCount() {
                 return newsCount;
        }

         public void setNewsCount( int newsCount) {
                 this.newsCount = newsCount;
        }

         public List getNewsList() {
                HttpClient httpClient = new HttpClient();
                GetMethod getMethod = new GetMethod(
                                 "http://www.ahcourt.gov.cn/gb/ahgy_2004/fyxw/index.html");
                getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER,
                                new DefaultHttpMethodRetryHandler());

                try {
                        int statusCode = httpClient.executeMethod(getMethod);
                        if (statusCode != HttpStatus.SC_OK) {
                                System.err
                                                .println("Method failed:" + getMethod.getStatusLine());
                        }

                        String responseBody = getMethod.getResponseBodyAsString();
                        responseBody = new String(responseBody.getBytes("ISO-8859-1"),
                                        "GB2312");
                        Source source = new Source(responseBody);

                        int tableCount = 0;

                        for (Iterator i = source.findAllElements(HTMLElementName.TABLE)
                                        .iterator(); i.hasNext(); tableCount++) {

                                Segment segment = (Segment) i.next();

                                if (tableCount == 13) {

                                        int hrefCount = 0;
                                        for (Iterator j = segment
                                                        .findAllElements(HTMLElementName.A).iterator(); j
                                                        .hasNext();) {
                                                Segment childsegment = (Segment) j.next();
                                                String title = childsegment.extractText();
                                                title.replace(" ", " ");
                                                title = trimTitle(title);
                                                Element childelement = (Element) childsegment;
                                                if (hrefCount < newsCount) {

                                                        String[] news = new String[] {
                                                                        title,
                                                                        "http://www.ahcourt.gov.cn"
                                                                                        + childelement
                                                                                                        .getAttributeValue("href") };
                                                        newsList.add(news);
                                                        hrefCount++;
                                                }
                                        }

                                }
                        }
                } catch (HttpException e) {
                        System.out.println("please check your provided http address!");
                        e.printStackTrace();
                } catch (IOException e) {
                        e.printStackTrace();
                } finally {
                        getMethod.releaseConnection();
                }
                return newsList;
        }

        private String trimTitle(String title) {
                String titlenew = "";

                for (int i = 0; i < title.length(); i++) {

                        if (Character.isSpaceChar(title.charAt(i)))
                                titlenew += " ";
                        else {
                                titlenew += title.charAt(i);
                        }

                }
                return titlenew;
        }
        public static void main(String[] args) {
                // TODO Auto-generated method stub
                CourtNews justice = new CourtNews();
                justice.setNewsCount(4);
                List list = justice.getNewsList();
                Iterator it = list.iterator();
                while (it.hasNext()) {
                        String[] news = (String[]) it.next();
                        System.out.println(news[0]);
                        System.out.println(news[1]);
        }
        }

}