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);    }}

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。