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
package my;

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：
package my;

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。