Lucene Example

LuceneExample.java

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.*;
import org.apache.lucene.index.*;
import org.apache.lucene.queryparser.flexible.core.QueryNodeException;
import org.apache.lucene.queryparser.flexible.standard.StandardQueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopScoreDocCollector;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;

import java.io.File;
import java.io.IOException;

public class LuceneExample {

    private final String INDEX_PATH = "the_index";
    private static final Version luceneVersion = Version.LUCENE_43;

    void run() throws IOException, QueryNodeException {
        Analyzer analyzer = new StandardAnalyzer(luceneVersion);

        Directory indexDir = FSDirectory.open(new File(INDEX_PATH));

        IndexWriterConfig luceneConfig = new IndexWriterConfig(luceneVersion, analyzer);
        IndexWriter writer = new IndexWriter(indexDir, luceneConfig);
        Document addDoc = new Document();
        addDoc.add(new StringField("id", "a1", Field.Store.YES));
        addDoc.add(new TextField("title", "Harry Potter", Field.Store.YES));
        addDoc.add(new TextField("author", "J. K. Rowling", Field.Store.YES));
        addDoc.add(new TextField("description", "Harry Potter is a series of seven fantasy novels", Field.Store.YES));

        Term term = new Term("id", "a1");
        writer.updateDocument(term, addDoc);
        writer.commit();
        writer.close();
        indexDir.close();

        StandardQueryParser queryParser = new StandardQueryParser();
        Query query = queryParser.parse("potter", "title");

        indexDir = FSDirectory.open(new File(INDEX_PATH));
        IndexReader reader = DirectoryReader.open(indexDir);
        System.out.println("Index numDocs: " + reader.numDocs());
        IndexSearcher searcher = new IndexSearcher(reader);

        int numHits = 100;
        TopScoreDocCollector collector = TopScoreDocCollector.create(numHits, true);
        searcher.search(query, collector);
        ScoreDoc[] docs = collector.topDocs().scoreDocs;

        System.out.println("Found " + docs.length + " docs.");
        for (ScoreDoc scoreDoc : docs) {
            Document foundDoc = searcher.doc(scoreDoc.doc);
            System.out.println(foundDoc.get("id") + "\t" + foundDoc.get("title"));
        }
    }

    public static void main(String[] args) {
        LuceneExample luceneExample = new LuceneExample();
        try {
            luceneExample.run();
        } catch (Exception e) {
            e.printStackTrace(System.err);
        }
    }
}