求一个思路，从网站上保存到本地

      //一直在使用和写PHP spider的爬虫程序。如果用JAVA写的话前台可以加入spider 页面



但是jaxa部分要删去，因PHP不是多线程。下面是网上转载的一个JAVA爬虫小例。很好的学习资料。



/**

* @author Jack.Wang

* 

*/

import java.io.BufferedReader;

import java.io.InputStreamReader;

import java.net.URL;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.HashSet;

import java.util.LinkedHashSet;

import java.util.regex.Matcher;

import java.util.regex.Pattern;



// 搜索Web爬行者

public class SearchCrawler implements Runnable {



/*

* disallowListCache缓存robot不允许搜索的URL。 Robot协议在Web站点的根目录下设置一个robots.txt文件,

* 规定站点上的哪些页面是限制搜索的。 

* 搜索程序应该在搜索过程中跳过这些区域,下面是robots.txt的一个例子: 

* # robots.txt for http://somehost.com/ User-agent:

* Disallow: /cgi-bin/ 

* Disallow: /registration # Disallow robots on registration page

* Disallow: /login

*/



private HashMap<String, ArrayList<String>> disallowListCache = new HashMap<String, ArrayList<String>>();

ArrayList<String> errorList = new ArrayList<String>();// 错误信息

ArrayList<String> result = new ArrayList<String>(); // 搜索到的结果

String startUrl;// 开始搜索的起点

int maxUrl;// 最大处理的url数

String searchString;// 要搜索的字符串(英文)

boolean caseSensitive = false;// 是否区分大小写

boolean limitHost = false;// 是否在限制的主机内搜索



public SearchCrawler(String startUrl, int maxUrl, String searchString) {

   this.startUrl = startUrl;

   this.maxUrl = maxUrl;

   this.searchString = searchString;

}



public ArrayList<String> getResult() {

   return result;

}



public void run() {// 启动搜索线程

   crawl(startUrl, maxUrl, searchString, limitHost, caseSensitive);

}



// 检测URL格式

private URL verifyUrl(String url) {

   // 只处理HTTP URLs.

   if (!url.toLowerCase().startsWith("http://"))

    return null;

   URL verifiedUrl = null;

   try {

    verifiedUrl = new URL(url);

   } catch (Exception e) {

    return null;

   }

   return verifiedUrl;

}



// 检测robot是否允许访问给出的URL.

private boolean isRobotAllowed(URL urlToCheck) {

   String host = urlToCheck.getHost().toLowerCase();// 获取给出RUL的主机

   // System.out.println("主机="+host);



   // 获取主机不允许搜索的URL缓存

   ArrayList<String> disallowList = disallowListCache.get(host);



   // 如果还没有缓存,下载并缓存。

   if (disallowList == null) {

    disallowList = new ArrayList<String>();

    try {

     URL robotsFileUrl = new URL("http://" + host + "/robots.txt");

     BufferedReader reader = new BufferedReader(

       new InputStreamReader(robotsFileUrl.openStream()));



     // 读robot文件，创建不允许访问的路径列表。

     String line;

     while ((line = reader.readLine()) != null) {

      if (line.indexOf("Disallow:") == 0) {// 是否包含"Disallow:"

       String disallowPath = line.substring("Disallow:"

         .length());// 获取不允许访问路径



       // 检查是否有注释。

       int commentIndex = disallowPath.indexOf("#");

       if (commentIndex != -1) {

        disallowPath = disallowPath.substring(0,

          commentIndex);// 去掉注释

       }



       disallowPath = disallowPath.trim();

       disallowList.add(disallowPath);

      }

     }



     // 缓存此主机不允许访问的路径。

     disallowListCache.put(host, disallowList);

    } catch (Exception e) {

     return true; // web站点根目录下没有robots.txt文件,返回真

    }

   }



   String file = urlToCheck.getFile();

   // System.out.println("文件getFile()="+file);

   for (int i = 0; i < disallowList.size(); i++) {

    String disallow = disallowList.get(i);

    if (file.startsWith(disallow)) {

     return false;

    }

   }



   return true;

}



private String downloadPage(URL pageUrl) {

   try {

    // Open connection to URL for reading.

    BufferedReader reader = new BufferedReader(new InputStreamReader(

      pageUrl.openStream()));



    // Read page into buffer.

    String line;

    StringBuffer pageBuffer = new StringBuffer();

    while ((line = reader.readLine()) != null) {

     pageBuffer.append(line);

    }



    return pageBuffer.toString();

   } catch (Exception e) {

   }



   return null;

}



// 从URL中去掉"www"

private String removeWwwFromUrl(String url) {

   int index = url.indexOf("://www.");

   if (index != -1) {

    return url.substring(0, index + 3) + url.substring(index + 7);

   }



   return (url);

}



// 解析页面并找出链接

private ArrayList<String> retrieveLinks(URL pageUrl, String pageContents,

    HashSet crawledList, boolean limitHost) {

   // 用正则表达式编译链接的匹配模式。

   Pattern p = Pattern.compile("<a\\s+href\\s*=\\s*\"?(.*?)[\"|>]",

     Pattern.CASE_INSENSITIVE);

   Matcher m = p.matcher(pageContents);



   ArrayList<String> linkList = new ArrayList<String>();

   while (m.find()) {

    String link = m.group(1).trim();



    if (link.length() < 1) {

     continue;

    }



    // 跳过链到本页面内链接。

    if (link.charAt(0) == '#') {

     continue;

    }



    if (link.indexOf("mailto:") != -1) {

     continue;

    }



    if (link.toLowerCase().indexOf("javascript") != -1) {

     continue;

    }



    if (link.indexOf("://") == -1) {

     if (link.charAt(0) == '/') {// 处理绝对地

      link = "http://" + pageUrl.getHost() + ":"

        + pageUrl.getPort() + link;

     } else {

      String file = pageUrl.getFile();

      if (file.indexOf('/') == -1) {// 处理相对地址

       link = "http://" + pageUrl.getHost() + ":"

         + pageUrl.getPort() + "/" + link;

      } else {

       String path = file.substring(0,

         file.lastIndexOf('/') + 1);

       link = "http://" + pageUrl.getHost() + ":"

         + pageUrl.getPort() + path + link;

      }

     }

    }



    int index = link.indexOf('#');

    if (index != -1) {

     link = link.substring(0, index);

    }



    link = removeWwwFromUrl(link);



    URL verifiedLink = verifyUrl(link);

    if (verifiedLink == null) {

     continue;

    }



    /* 如果限定主机，排除那些不合条件的URL */

    if (limitHost

      && !pageUrl.getHost().toLowerCase().equals(

        verifiedLink.getHost().toLowerCase())) {

     continue;

    }



    // 跳过那些已经处理的链接.

    if (crawledList.contains(link)) {

     continue;

    }



    linkList.add(link);

   }



   return (linkList);

}



// 搜索下载Web页面的内容，判断在该页面内有没有指定的搜索字符串



private boolean searchStringMatches(String pageContents,

    String searchString, boolean caseSensitive) {

   String searchContents = pageContents;

   if (!caseSensitive) {// 如果不区分大小写

    searchContents = pageContents.toLowerCase();

   }



   Pattern p = Pattern.compile("[\\s]+");

   String[] terms = p.split(searchString);

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

    if (caseSensitive) {

     if (searchContents.indexOf(terms[i]) == -1) {

      return false;

     }

    } else {

     if (searchContents.indexOf(terms[i].toLowerCase()) == -1) {

      return false;

     }

    }

   }



   return true;

}



// 执行实际的搜索操作

public ArrayList<String> crawl(String startUrl, int maxUrls,

    String searchString, boolean limithost, boolean caseSensitive) {



   HashSet<String> crawledList = new HashSet<String>();

   LinkedHashSet<String> toCrawlList = new LinkedHashSet<String>();



   if (maxUrls < 1) {

    errorList.add("Invalid Max URLs value.");

    System.out.println("Invalid Max URLs value.");

   }



   if (searchString.length() < 1) {

    errorList.add("Missing Search String.");

    System.out.println("Missing search String");

   }



   if (errorList.size() > 0) {

    System.out.println("err!!!");

    return errorList;

   }



   // 从开始URL中移出www

   startUrl = removeWwwFromUrl(startUrl);



   toCrawlList.add(startUrl);

   while (toCrawlList.size() > 0) {



    if (maxUrls != -1) {

     if (crawledList.size() == maxUrls) {

      break;

     }

    }



    // Get URL at bottom of the list.

    String url = toCrawlList.iterator().next();



    // Remove URL from the to crawl list.

    toCrawlList.remove(url);



    // Convert string url to URL object.

    URL verifiedUrl = verifyUrl(url);



    // Skip URL if robots are not allowed to access it.

    if (!isRobotAllowed(verifiedUrl)) {

     continue;

    }



    // 增加已处理的URL到crawledList

    crawledList.add(url);

    String pageContents = downloadPage(verifiedUrl);



    if (pageContents != null && pageContents.length() > 0) {

     // 从页面中获取有效的链接

     ArrayList<String> links = retrieveLinks(verifiedUrl,

       pageContents, crawledList, limitHost);



     toCrawlList.addAll(links);



     if (searchStringMatches(pageContents, searchString,

       caseSensitive)) {

      result.add(url);

      System.out.println(url);

     }

    }



   }

   return result;

}



// 主函数

public static void main(String[] args) { 

   SearchCrawler crawler = new SearchCrawler("http://www.blogjava.net/Jack2007/", 20,"jack");

   Thread search = new Thread(crawler);

   System.out.println("Start searching...");

   System.out.println("result:");

   search.start();

   try {

    search.join();

   } catch (InterruptedException e) {

    // TODO Auto-generated catch block

    e.printStackTrace();

   }

}

}