www.pudn.com > SearchCr.zip > SearchCrawler.java

import java.util.*; 
import java.net.*; 
import java.io.*; 
import java.util.regex.*; 
 
// 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> disallowListCache = new HashMap>();  
  ArrayList errorList= new ArrayList();//错误信息  
  ArrayList result=new ArrayList(); //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 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 disallowList =disallowListCache.get(host);  
 
    // 如果还没有缓存,下载并缓存。  
    if (disallowList == null) {  
      disallowList = new ArrayList();  
      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 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("]",Pattern.CASE_INSENSITIVE); 
    Matcher m = p.matcher(pageContents); 
 
     
    ArrayList linkList = new ArrayList(); 
    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 crawl(String startUrl, int maxUrls, String searchString,boolean limithost,boolean caseSensitive ) 
  {  
     
    System.out.println("searchString="+searchString); 
    HashSet crawledList = new HashSet(); 
    LinkedHashSet toCrawlList = new LinkedHashSet(); 
 
     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 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) { 
     if(args.length!=3){ 
        System.out.println("Usage:java SearchCrawler startUrl maxUrl searchString"); 
        return; 
     } 
    int max=Integer.parseInt(args[1]); 
    SearchCrawler crawler = new SearchCrawler(args[0],max,args[2]); 
    Thread  search=new Thread(crawler); 
    System.out.println("Start searching..."); 
    System.out.println("result:"); 
    search.start(); 
    
  } 
}