apache lucene 一个最简单的实例

就像每个程序都有一个Hello World来让人体验它一样，lucene也可以很简单的提供一个实例。如下（来自lucene in action的例子）有两个类组成：
一个是建立索引

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.Date;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexWriter;

public class Indexer {
  public static void main(String[] args) throws Exception {
    if (args.length != 2) {
      throw new Exception("Usage: java " + Indexer.class.getName() + " <index dir> <data dir>");
    }
    File indexDir = new File(args[0]);
    File dataDir = new File(args[1]);
    long start = new Date().getTime();
    int numIndexed = index(indexDir, dataDir);
    long end = new Date().getTime();
    System.out.println("Indexing " + numIndexed + " files took " + (end - start) + " milliseconds");
  }

  // open an index and start file directory traversal
  public static int index(File indexDir, File dataDir) throws IOException {
    if (!dataDir.exists() || !dataDir.isDirectory()) {
      throw new IOException(dataDir + " does not exist or is not a directory");
    }
    IndexWriter writer = new IndexWriter(indexDir, new StandardAnalyzer(), true);
    writer.setUseCompoundFile(false);
    indexDirectory(writer, dataDir);
    int numIndexed = writer.docCount();
    writer.optimize();
    writer.close();
    return numIndexed;
  }

  // recursive method that calls itself when it finds a directory
  private static void indexDirectory(IndexWriter writer, File dir) throws IOException {
    File[] files = dir.listFiles();
    for (int i = 0; i < files.length; i++) {
      File f = files[i];
      if (f.isDirectory()) {
        indexDirectory(writer, f);
      } else if (f.getName().endsWith(".txt")) {
        indexFile(writer, f);
      }
    }
  }

  // method to actually index file using Lucene
  private static void indexFile(IndexWriter writer, File f) throws IOException {
    if (f.isHidden() || !f.exists() || !f.canRead()) {
      return;
    }
    System.out.println("Indexing " + f.getCanonicalPath());
    Document doc = new Document();
    doc.add(Field.Text("contents", new FileReader(f)));
    doc.add(Field.Keyword("filename", f.getCanonicalPath()));
    writer.addDocument(doc);
  }
}

另一个是搜索：

 
import java.io.File;
import java.util.Date;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.queryParser.QueryParser;
import org.apache.lucene.search.Hits;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
public class Searcher {
  public static void main(String[] args) throws Exception {
    if (args.length != 2) {
      throw new Exception("Usage: java " + Searcher.class.getName() + " <index dir> <auery>");
    }
    File indexDir = new File(args[0]);
    String q = args[1];
    if (!indexDir.exists() || !indexDir.isDirectory()) {
      throw new Exception(indexDir + " does not exist or is not a directory.");
    }
    search(indexDir, q);
  }
  public static void search(File indexDir, String q) throws Exception {
    Directory fsDir = FSDirectory.getDirectory(indexDir, false);
    IndexSearcher is = new IndexSearcher(fsDir);
    Query query = QueryParser.parse(q, "contents", new StandardAnalyzer());
    long start = new Date().getTime();
    Hits hits = is.search(query);
    long end = new Date().getTime();
    System.err.println("Found " + hits.length() + " document(s) (in " + (end - start) + " milliseconds) that matched query ‘"
        + q + "’:");
    for (int i = 0; i < hits.length(); i++) {
      Document doc = hits.doc(i);
      System.out.println(doc.get("filename"));
    }
  }
}

ok，这样就简单实现了，在搜索目录下所有txt，找出包括某一个字符串的txt文件名的功能。
下篇文章将介绍一下lucene的核心类