hotbot.java

一个Web爬虫（机器人

/*
 * WebSPHINX web crawling toolkit
 * Copyright (C) 1998,1999 Carnegie Mellon University 
 * 
 * This library is free software; you can redistribute it
 * and/or modify it under the terms of the GNU Library
 * General Public License as published by the Free Software 
 * Foundation, version 2.
 *
 * WebSPHINX homepage: http://www.cs.cmu.edu/~rcm/websphinx/
 */
package websphinx.searchengine;

import websphinx.*;
import java.net.URL;
import java.net.URLEncoder;
import java.net.MalformedURLException;

/**
 * <A href="http://www.hotbot.com/">HotBot</a> search engine.
 */
public class HotBot implements SearchEngine {

    static Pattern patTitle = new Regexp ("^");

    static Pattern patCount = new Regexp (
        "Returned <B>(\\d+)</b> matches"
    );
    static Pattern patNoHits = new Regexp (
        "Sorry -- your search yielded no results"
    );

    // FIX: works only for Netscape
    static Pattern patResult = new Tagexp (
      "<td><b>(?{rank})</b></td>" // rank
    + "<td>(?:<a><img></a>)?"     // optional icon
    + "(?{link}<a>(?{title})</a>)</td>" // title and main link
    + "</tr><tr><td><font>(?{score})</font></td><td>(?{description})<br></td>" // description
    );

    static Pattern patMoreLink = new Tagexp (
        "<input type=image name=act.next>"
    );

    /**
     * Classify a page.  Sets the following labels:
     * <TABLE>
     * <TR><TH>Name <TH>Type  <TH>Meaning
     * <TR><TD>searchengine.source <TD>Page label <TD>HotBot object that labeled this page
     * <TR><TD>searchengine.count <TD>Page field <TD>Number of results on page
     * <TR><TD>searchengine.results <TD>Page fields <TD>Array of results.  Each result region
     * contains subfields: rank, title, description, and link.
     * <TR><TD>searchengine.more-results <TD>Link label <TD>Link to a page containing more results.
     * </TABLE>
     */
    public void classify (Page page) {
        String title = page.getTitle ();
        if (title != null && title.startsWith ("HotBot results:")) {
            page.setObjectLabel ("searchengine.source", this);

            Region count = patCount.oneMatch (page);
            if (count != null)
                page.setField ("searchengine.count", count.getField ("0"));
            
            Region[] results = patResult.allMatches (page);
            //System.err.println ("found " + results.length + " results");
            SearchEngineResult[] ser = new SearchEngineResult[results.length];
            for (int i=0; i<results.length; ++i) {
                ser[i] = new SearchEngineResult (results[i]);
                //System.out.println (ser[i]);
            }
            page.setFields ("searchengine.results", ser);

            PatternMatcher m = patMoreLink.match (page);
            while (m.hasMoreElements ()) {
                Link link = (Link)m.nextMatch ();
                link.setLabel ("searchengine.more-results");
                link.setLabel ("hyperlink");             
            }
        }
        else System.err.println ("not a HotBot page");

    }

    /**
     * Priority of this classifier.
     */
    public static final float priority = 0.0F;
    
    /**
     * Get priority of this classifier.
     * @return priority.
     */
    public float getPriority () {
        return priority;
    }

    /**
     * Make a query URL for HotBot.
     * @param keywords list of keywords, separated by spaces
     * @return URL that submits the keywords to HotBot.
     */
    public URL makeQuery (String keywords) {
        try {
            return new URL("http://www.search.hotbot.com/hResult.html/?SM=MC&MT="
                           + URLEncoder.encode(keywords)
                           + "&DV=7&RG=.com&DC=10&DE=2&OPs=MDRTP&_v=2&DU=days&SW=web");
        } catch (MalformedURLException e) {
            throw new RuntimeException ("internal error");
        }
    }

    /**
     * Get number of results per page for this search engine.
     * @return typical number of results per page
     */
    public int getResultsPerPage () {
        return 10;
    }

    /**
     * Search HotBot.
     * @param keywords list of keywords, separated by spaces
     * @return enumeration of SearchEngineResults returned by a HotBot query constructed from the keywords.
     */
    public static Search search (String keywords) {
        return new Search (new HotBot(), keywords);
    }

    /**
     * Search HotBot.
     * @param keywords list of keywords, separated by spaces
     * @param maxResults maximum number of results to return
     * @return enumeration of SearchEngineResults returned by an HotBot query constructed from the keywords.
     * The enumeration yields at most maxResults objects.
     */
    public static Search search (String keywords, int maxResults) {
        return new Search (new HotBot(), keywords, maxResults);
    }
}