Nutch1.2标题关键字高亮的正确方法

最近在弄Nutch1.2，实现关键字高亮，却发现标题关键字高亮的方法，国内网站上的都是错的,最终在nutch.apache.org网站找到了相近的代码，进行修改，终于成功完成
关键字的高亮需要自己再创建一个分词器,关键的类是TokenStream,lucene3.0以上需要用到TermAttribute。

一、内容关键字高亮很简单，修改include/style.html即可：

   .highlight {
          color:#FF0000;
   }

二、标题关键字高亮的方法：

     我们从内容关键字高亮的方法可以得到启发：

     首先来看这一句：

     String summary = summaries[i].toHtml(true);

     这个是调用了org.apache.nutch.searcher.Summary方法
     public String toHtml(boolean encode)｛...｝

     这是标题的获取方法

     String title = detail.getValue("title");

     我们可不可以也像summary一样调用呢，答案是肯定的,但是,nutch本身并未提标题关键字高亮的方法，这里需要我们写类和方法。

     新建Titler.java
   
package org.apache.nutch.searcher;

import java.io.IOException;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.HashSet;

import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.Token;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.TermAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
import org.apache.nutch.analysis.NutchDocumentAnalyzer;
import org.apache.nutch.searcher.Summary.Fragment;

public class Titler implements Configurable {

    private int maxLength = 40;
    private Analyzer analyzer = null;
    private Configuration conf = null;

    public Titler(Configuration conf) {
        setConf(conf);
    }

    public Configuration getConf() {
        return conf;
    }

    public void setConf(Configuration conf) {
        this.conf = conf;
        this.analyzer = new NutchDocumentAnalyzer(conf);
        this.maxLength = conf.getInt("searcher.title.maxlength", 40);
    }

    public Summary getSummary(String text, Query query) {
        Token[] tokens = getTokens(text); // parse text to token array

        if (tokens.length == 0)
            return new Summary();

        String[] terms = query.getTerms();
        HashSet highlight = new HashSet(); // put query terms in table
        for (int i = 0; i < terms.length; i++)
            highlight.add(terms[i]);

        Summary s = new Summary();
       
        for (int i = 0; i < tokens.length && i < maxLength; i++) {
            Token token = tokens[i];
            //
            // If we find a term that's in the query...
            //
            if (highlight.contains(token.term())) {
                s.add(new Highlight(token.term()));   
            }else{
                s.add(new Fragment(token.term()));
            }
        }
        return s;
    }

    /** A highlighted fragment of text within a summary. */
    public static class Highlight extends Fragment {
        /** Constructs a highlighted fragment for the given text. */
        public Highlight(String text) {
            super(text);
        }
        /** Returns true. */
        public boolean isHighlight() {
            return true;
        }
    }

    private Token[] getTokens(String text) {
        ArrayList result = new ArrayList();
        TokenStream ts = analyzer.tokenStream("title", new StringReader(text));

        TermAttribute termAtt = (TermAttribute) ts
                .getAttribute(TermAttribute.class);
        TypeAttribute typeAtt = (TypeAttribute) ts
                .getAttribute(TypeAttribute.class);

        try {
            while (ts.incrementToken()) {
                Token token = new Token();
                token.setTermBuffer(termAtt.term());
                result.add(token);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return (Token[]) result.toArray(new Token[result.size()]);
    }
}


     然后在NutchBean.java，添加
    
     private Titler titler;

     public Summary getTitle(HitDetails hit, Query query) throws IOException {
    return titler.getSummary(hit.getValue("title"), query);
     }

     public NutchBean(Configuration conf, Path dir) throws IOException {
        ...
        this.titler = new Titler(conf);
     }

     我这里测试的JSP页面是新建s.jsp.如果要在原来的search.jsp页面内调用，需要修改相应的代码。

<%@ page
  session="false"
  contentType="text/html; charset=UTF-8"
  pageEncoding="UTF-8"

  import="java.io.*"
  import="java.util.*"
  import="java.net.*"
  import="javax.servlet.http.*"
  import="javax.servlet.*"

  import="org.apache.nutch.html.Entities"
  import="org.apache.nutch.metadata.Nutch"
  import="org.apache.nutch.searcher.*"
  import="org.apache.nutch.plugin.*"
  import="org.apache.nutch.clustering.*"
  import="org.apache.hadoop.conf.*"
  import="org.apache.nutch.util.NutchConfiguration"
%>
<jsp:include page="/show/include/style.html"/>
<%

        String keyword = "贵阳pep艺术中心― 中心简介";
        String crawl = "/home/961a/workspace/test/Nutch1.2Web/ROOT/crawl";
        String summarylength = "120";

        final Configuration conf = NutchConfiguration.create();
        conf.set("searcher.dir", crawl);
        conf.set("searcher.summary.length", summarylength);

        final NutchBean bean = new NutchBean(conf);
        try {
            final Query query = Query.parse(keyword, conf);
            query.getParams().setMaxHitsPerDup(0);
            final Hits hits = bean.search(query);

            out.println("Total hits: " + hits.getTotal() + "  keyword:贵阳pep艺术中心― 中心简介;<BR>");

            final int length = (int) Math.min(hits.getLength(), 10);
            final Hit[] show = hits.getHits(0, length);
            final HitDetails[] details = bean.getDetails(show);
            final Summary[] summaries = bean.getSummary(details, query);

            for (int i = 0; i < hits.getLength(); i++) {
                String url = Entities.encode(details[i].getValue("url"));
                String title = bean.getTitle(details[i], query).toHtml(true);
                String summary = summaries[i].toHtml(true);
                %>
                <p>
                <span class="title"><a href="<%=url%>"><%=title%></a></span>
                <br>
                <span class="bodytext"><%=summary%></span>
                <br>
                <span class="url"><%=Entities.encode(details[i].getValue("url"))%></span>
                </p>
                <%
            }
        } catch (Throwable t) {
        }%>