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。如果读者有改进办法可以把源代码帖出,不胜感激。
附上源代码如下(保存名为GetWeb.java):
import java.io.File; import java.io.BufferedReader; 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.regex.Matcher; import java.util.regex.Pattern; import java.util.Hashtable; 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(); } } 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)+""); } } } }
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