关于初次了解搜索引擎---爬虫

package com;
/*
以下是一个Java爬虫程序，它能从指定主页开始，按照指定的深度抓取该站点域名下的网页并维护简单索引。
参数：private static int webDepth = 2;//爬虫深度。主页的深度为1，设置深度后超过该深度的网页不会抓取。
     private int intThreadNum = 10;//线程数。开启的线程数。

抓取时也会在程序源文件目录下生成一个report.txt文件记录爬虫的运行情况，并在抓取结束后生成一个fileindex.txt
文件维护网页文件索引。

本程序用到了多线程(静态变量和同步)，泛型，文件操作，URL类和连接，Hashtable类关联数组，正则表达式及其相关类。
运行时需使用命令行参数，第一个参数应使用http://开头的有效URL字符串作为爬虫的主页，第二个参数（可选）
应输入可转换为int型的字符串（用Integer.parseInt(String s)静态方法可以转换的字符串，如3）作为爬虫深度，
如果没有，则默认深度为2。

本程序的不足之处是：只考虑了href= href=' href="后加绝对url的这三种情况(由于url地址在网页源文件中情况比
较复杂，有时处理也会出现错误)，还有相对url和window.open('的情况没有考虑。异常处理程序也只是简单处理。


附上源代码如下（保存名为GetWeb.java）：

*/

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class GetWeb {
private int webDepth = 2;// 爬虫深度
private int intThreadNum = 10;// 线程数
private String strHomePage = "";// 主页地址
private String myDomain;// 域名
private String fPath = "web";// 储存网页文件的目录名
private ArrayList<String> arrUrls = new ArrayList<String>();// 存储未处理URL
private ArrayList<String> arrUrl = new ArrayList<String>();// 存储所有URL供建立索引
private Hashtable<String, Integer> allUrls = new Hashtable<String, Integer>();// 存储所有URL的网页号
private Hashtable<String, Integer> deepUrls = new Hashtable<String, Integer>();// 存储所有URL深度
private int intWebIndex = 0;// 网页对应文件下标，从0开始
private String charset = "GB2312";
private String report = "";
private long startTime;
private int webSuccessed = 0;
private int webFailed = 0;

public GetWeb(String s) {
   this.strHomePage = s;
}

public GetWeb(String s, int i) {
   this.strHomePage = s;
   this.webDepth = i;
}

public synchronized void addWebSuccessed() {
   webSuccessed++;
}

public synchronized void addWebFailed() {
   webFailed++;
}

public synchronized void addReport(String s) {
   try {
    report += s;
    PrintWriter pwReport = new PrintWriter(new FileOutputStream(
      "report.txt"));
    pwReport.println(report);
    pwReport.close();
   } catch (Exception e) {
    System.out.println("生成报告文件失败!");
   }
}

public synchronized String getAUrl() {
   String tmpAUrl = arrUrls.get(0);
   arrUrls.remove(0);
   return tmpAUrl;
}

public synchronized String getUrl() {
   String tmpUrl = arrUrl.get(0);
   arrUrl.remove(0);
   return tmpUrl;
}

public synchronized Integer getIntWebIndex() {
   intWebIndex++;
   return intWebIndex;
}

/**
* @param args
*/
public static void main(String[] args) {
   /*if (args.length == 0 || args[0].equals("")) {
    System.out.println("No input!");
    System.exit(1);
   } else if (args.length == 1) {
    GetWeb gw = new GetWeb(args[0]);
    gw.getWebByHomePage();
   } else {
    GetWeb gw = new GetWeb(args[0], Integer.parseInt(args[1]));
    gw.getWebByHomePage();
   }*/
   Scanner cin=new Scanner(System.in);
   String url = cin.next();
   int webDepth = cin.nextInt();
  
   GetWeb gw = new GetWeb(url, webDepth);
   gw.getWebByHomePage();
}

public void getWebByHomePage() {
   startTime = System.currentTimeMillis();
   this.myDomain = getDomain();
   if (myDomain == null) {
    System.out.println("Wrong input!");
    // System.exit(1);
    return;
   }
   System.out.println("Homepage = " + strHomePage);
   addReport("Homepage = " + strHomePage + "!\n");
   System.out.println("Domain = " + myDomain);
   addReport("Domain = " + myDomain + "!\n");
   arrUrls.add(strHomePage);
   arrUrl.add(strHomePage);
   allUrls.put(strHomePage, 0);
   deepUrls.put(strHomePage, 1);
   File fDir = new File(fPath);
   if (!fDir.exists()) {
    fDir.mkdir();
   }
   System.out.println("Start!");
   this.addReport("Start!\n");
   String tmp = getAUrl();
   this.getWebByUrl(tmp, charset, allUrls.get(tmp) + "");
   int i = 0;
   for (i = 0; i < intThreadNum; i++) {
    new Thread(new Processer(this)).start();
   }
   while (true) {
    if (arrUrls.isEmpty() && Thread.activeCount() == 1) {
     long finishTime = System.currentTimeMillis();
     long costTime = finishTime - startTime;
     System.out.println("\n\n\n\n\nFinished!");
     addReport("\n\n\n\n\nFinished!\n");
     System.out.println("Start time = " + startTime + "   "
       + "Finish time = " + finishTime + "   "
       + "Cost time = " + costTime + "ms");
     addReport("Start time = " + startTime + "   "
       + "Finish time = " + finishTime + "   "
       + "Cost time = " + costTime + "ms" + "\n");
     System.out.println("Total url number = "
       + (webSuccessed + webFailed) + "   Successed: "
       + webSuccessed + "   Failed: " + webFailed);
     addReport("Total url number = " + (webSuccessed + webFailed)
       + "   Successed: " + webSuccessed + "   Failed: "
       + webFailed + "\n");

     String strIndex = "";
     String tmpUrl = "";
     while (!arrUrl.isEmpty()) {
      tmpUrl = getUrl();
      strIndex += "Web depth:" + deepUrls.get(tmpUrl)
        + "   Filepath: " + fPath + "/web"
        + allUrls.get(tmpUrl) + ".htm" + "   url:" + tmpUrl
        + "\n\n";
     }
     System.out.println(strIndex);
     try {
      PrintWriter pwIndex = new PrintWriter(new FileOutputStream(
        "fileindex.txt"));
      pwIndex.println(strIndex);
      pwIndex.close();
     } catch (Exception e) {
      System.out.println("生成索引文件失败!");
     }
     break;
    }
   }
}

public void getWebByUrl(String strUrl, String charset, String fileIndex) {
   try {
    // if(charset==null||"".equals(charset))charset="utf-8";
    System.out.println("Getting web by url: " + strUrl);
    addReport("Getting web by url: " + strUrl + "\n");
    URL url = new URL(strUrl);
    URLConnection conn = url.openConnection();
    conn.setDoOutput(true);
    InputStream is = null;
    is = url.openStream();

    String filePath = fPath + "/web" + fileIndex + ".htm";
    PrintWriter pw = null;
    FileOutputStream fos = new FileOutputStream(filePath);
    OutputStreamWriter writer = new OutputStreamWriter(fos);
    pw = new PrintWriter(writer);
    BufferedReader bReader = new BufferedReader(new InputStreamReader(
      is));
    StringBuffer sb = new StringBuffer();
    String rLine = null;
    String tmp_rLine = null;
    while ((rLine = bReader.readLine()) != null) {
     tmp_rLine = rLine;
     int str_len = tmp_rLine.length();
     if (str_len > 0) {
      sb.append("\n" + tmp_rLine);
      pw.println(tmp_rLine);
      pw.flush();
      if (deepUrls.get(strUrl) < webDepth)
       getUrlByString(tmp_rLine, strUrl);
     }
     tmp_rLine = null;
    }
    is.close();
    pw.close();
    System.out.println("Get web successfully! " + strUrl);
    addReport("Get web successfully! " + strUrl + "\n");
    addWebSuccessed();
   } catch (Exception e) {
    System.out.println("Get web failed!       " + strUrl);
    addReport("Get web failed!       " + strUrl + "\n");
    addWebFailed();
   }
}

public String getDomain() {
   String reg = "(?<=http\\://[a-zA-Z0-9]{0,100}[.]{0,1})[^.\\s]*?\\.(com|cn|net|org|biz|info|cc|tv)";
   Pattern p = Pattern.compile(reg, Pattern.CASE_INSENSITIVE);
   Matcher m = p.matcher(strHomePage);
   boolean blnp = m.find();
   if (blnp == true) {
    return m.group(0);
   }
   return null;
}

public void getUrlByString(String inputArgs, String strUrl) {
   String tmpStr = inputArgs;
   String regUrl = "(?<=(href=)[\"]?[\']?)[http://][^\\s\"\'\\?]*("
     + myDomain + ")[^\\s\"\'>]*";
   Pattern p = Pattern.compile(regUrl, Pattern.CASE_INSENSITIVE);
   Matcher m = p.matcher(tmpStr);
   boolean blnp = m.find();
   // int i = 0;
   while (blnp == true) {
    if (!allUrls.containsKey(m.group(0))) {
     System.out.println("Find a new url,depth:"
       + (deepUrls.get(strUrl) + 1) + " " + m.group(0));
     addReport("Find a new url,depth:" + (deepUrls.get(strUrl) + 1)
       + " " + m.group(0) + "\n");
     arrUrls.add(m.group(0));
     arrUrl.add(m.group(0));
     allUrls.put(m.group(0), getIntWebIndex());
     deepUrls.put(m.group(0), (deepUrls.get(strUrl) + 1));
    }
    tmpStr = tmpStr.substring(m.end(), tmpStr.length());
    m = p.matcher(tmpStr);
    blnp = m.find();
   }
}

class Processer implements Runnable {
   GetWeb gw;

   public Processer(GetWeb g) {
    this.gw = g;
   }

   public void run() {
    // Thread.sleep(5000);
    while (!arrUrls.isEmpty()) {
     String tmp = getAUrl();
     getWebByUrl(tmp, charset, allUrls.get(tmp) + "");
    }
   }
}
}

转载至：http://hi.baidu.com/yxh265/blog/item/27820203ece6d4074bfb51a1.html