使用开源组件搭建搜索引擎

在开发中小型搜索引擎的过程中，我使用由Java开发的开源软件：jspider,htmlparser,lucence,IKAnalyzer，下面我一一道来。

lucence很著名啦，不必多说，我写的这个引擎就是在它自带的demo基础上重构的。

jspider顾名思义，是一个用Java开发的爬虫。

htmlparser是解析html页面的，因为lucene自带的html解析器不够健壮，所以用了这个。

 IKAnalyzer是为lucence定做的中文分词组件，在使用中我发现效果不错。

具体的编码下次再说吧，呵呵

接着说。
用jspider从新浪和163开始爬了大约200M的材料，作为构建搜索引擎的基础，我开始了自己的搜索引擎之路。

剩下的工作就是建立索引和利用索引提供查询服务。

建立索引
我首先分析了
lucene-2.1.0\src\demo\org\apache\lucene\demo\IndexHtml.java
这个文件提供了很好的实例，我简单重构了一下就可以用了

import org.mira.lucene.analysis.MIK_CAnalyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.demo.HTMLDocument;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;

import java.io.File;
import java.util.Date;
import java.util.Arrays;

/** Indexer for HTML files. */
public class IndexHTML {
  private IndexHTML() {}

  private static boolean deleting = false;   // true during deletion pass
  private static IndexReader reader;   // existing index
  private static IndexWriter writer;   // new index being built
  private static TermEnum uidIter;   // document id iterator

  /** Indexer for HTML files.*/
  public static void main(String[] argv) {
    try {
      String index = "index";
      boolean create = true;
      File root = null;
     

      String usage = "IndexHTML [-create] [-index <index>] <root_directory>";
/*
      if (argv.length == 0) {
        System.err.println("Usage: " + usage);
        return;
      }

      for (int i = 0; i < argv.length; i++) {
        if (argv[i].equals("-index")) {   // parse -index option
          index = argv[++i];
        } else if (argv[i].equals("-create")) {   // parse -create option
          create = true;
        } else if (i != argv.length-1) {
          System.err.println("Usage: " + usage);
          return;
        } else
          root = new File(argv[i]);
      }
*/
      Date start = new Date();
      root = new File("c://tes1");
      index = "c://index1";
      if (!create) {   // delete stale docs
        deleting = true;
        indexDocs(root, index, create);
      }
      writer = new IndexWriter(index, new MIK_CAnalyzer(), create);
      writer.setMaxBufferedDocs(30);
      writer.setMergeFactor(100);
      writer.setMaxFieldLength(1000000);
      indexDocs(root, index, create);   // add new docs

      System.out.println("Optimizing index...");
     
      writer.optimize();
      writer.close();

      Date end = new Date();

      System.out.print(end.getTime() - start.getTime());
      System.out.println(" total milliseconds");

    } catch (Exception e) {
      System.out.println(" caught a " + e.getClass() +
          "\n with message: " + e.getMessage());
    }
  }

  /* Walk directory hierarchy in uid order, while keeping uid iterator from
  /* existing index in sync.  Mismatches indicate one of: (a) old documents to
  /* be deleted; (b) unchanged documents, to be left alone; or (c) new
  /* documents, to be indexed.
   */

  private static void indexDocs(File file, String index, boolean create)
       throws Exception {
    if (!create) {   // incrementally update

      reader = IndexReader.open(index);   // open existing index
      uidIter = reader.terms(new Term("uid", "")); // init uid iterator

      indexDocs(file);

      if (deleting) {   // delete rest of stale docs
        while (uidIter.term() != null && uidIter.term().field() == "uid") {
          System.out.println("deleting " +
              HTMLDocument.uid2url(uidIter.term().text()));
          reader.deleteDocuments(uidIter.term());
          uidIter.next();
        }
        deleting = false;
      }

      uidIter.close();   // close uid iterator
      reader.close();   // close existing index

    } else   // don't have exisiting
      indexDocs(file);
  }

  private static void indexDocs(File file) throws Exception {
    if (file.isDirectory()) {   // if a directory
      String[] files = file.list();   // list its files
      Arrays.sort(files);   // sort the files
      for (int i = 0; i < files.length; i++)   // recursively index them
        indexDocs(new File(file, files[i]));

    } else if (file.getPath().endsWith(".html") || // index .html files
      file.getPath().endsWith(".htm") || // index .htm files
      file.getPath().endsWith(".txt")) { // index .txt files

      if (uidIter != null) {
        String uid = HTMLDocument.uid(file);   // construct uid for doc

        while (uidIter.term() != null && uidIter.term().field() == "uid" &&
            uidIter.term().text().compareTo(uid) < 0) {
          if (deleting) {   // delete stale docs
            System.out.println("deleting " +
                HTMLDocument.uid2url(uidIter.term().text()));
            reader.deleteDocuments(uidIter.term());
          }
          uidIter.next();
        }
        if (uidIter.term() != null && uidIter.term().field() == "uid" &&
            uidIter.term().text().compareTo(uid) == 0) {
          uidIter.next();   // keep matching docs
        } else if (!deleting) {   // add new docs
          Document doc = HTMLDocument.Document(file);
          System.out.println("adding " + doc.get("path"));
          writer.addDocument(doc);
        }
      } else {   // creating a new index
        Document doc = HTMLDocument.Document(file);
        System.out.println("adding " + doc.get("path"));
        writer.addDocument(doc);   // add docs unconditionally
      }
    }
  }
}

从源代码可以看到，中文分词已经加进去了，
而索引HTML的关键工作是由 HTMLDocument这个类完成的，需要对它进行重构

这个时候，htmlparser闪亮登场

请说jspider只能是对HTML的url进行检索，
是嘛，
不知道Heritrix这个怎么样呢，对比起来！！