用java写一个程序爬取一个网页的内容

Question

要爬取http://epaper.632news.com/zzrb/html/2016-06/07/node_2.htm这个页面，要整个页面的内容，用java程序

Answer 1

 package com.hanxb.crawler;

import java.util.*;
import java.net.*;
import java.io.*;
import java.util.regex.*;

// 搜索Web爬行者
public class NativeCrawler 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
    public ArrayList<String> getResult() {
        return result;
    }

    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 NativeCrawler(String startUrl, int maxUrl, String searchString) {
        this.startUrl = startUrl;
        this.maxUrl = maxUrl;
        this.searchString = searchString;
    }

    public void run() {// 启动搜索线程
        crawl(startUrl, maxUrl, searchString, limitHost, caseSensitive);
    }

    // 执行实际的搜索操作
    public ArrayList<String> crawl(String startUrl, int maxUrls,
            String searchString, boolean limithost, boolean caseSensitive) {

        System.out.println("searchString=" + searchString);

        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;
    }

    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;
    }

    // 在Web页面的内容中，判断是否存在指定的字符串
    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;
    }

    // 检测URL格式
    private URL verifyUrl(String url) {
        // 只处理HTTPS URLs.
        if (!url.toLowerCase().startsWith("https://"))
            return null;

        URL verifiedUrl = null;
        try {
            verifiedUrl = new URL(url);
        } catch (Exception e) {
            return null;//not needed
        }

        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;
    }

    // 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<String> 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);
    }

    // 主函数
    public static void main(String[] args) {
        if (args.length != 3) {
            System.out
                    .println("Usage:java NativeCrawler startUrl maxUrl searchString");
            return;
        }
        int max = Integer.parseInt(args[1]);
        NativeCrawler crawler = new NativeCrawler(args[0], max, args[2]);
        Thread search = new Thread(crawler);
        System.out.println("Start searching...");
        System.out.println("result:");
        search.start();

    }
}