lucene Getting started with lucene

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Hello World

This basic Lucene example creates a simple index, and searches on it.

Note: RAMDirectory creates a memory-resident index, and is handy for experimenting and testing, but in practice most people will need to have an index stored in the file system (see FSDirectory.open).

import java.io.IOException;
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.classic.*;
import org.apache.lucene.search.*;
import org.apache.lucene.store.*;

public class HelloLucene {
    public static void main(String[] args) throws IOException, ParseException
    {
        //Create a new index and open a writer
        Directory dir = new RAMDirectory();
        Analyzer analyzer = new StandardAnalyzer();
        IndexWriterConfig config = new IndexWriterConfig(analyzer);
        IndexWriter writer = new IndexWriter(dir, config);
    
        //Create a document to index
        Document doc = new Document();
        doc.add(new TextField("text", "Hello World!", Field.Store.YES));
    
        //Index the document and close the writer
        System.out.println("Indexing document: " + doc);
        writer.addDocument(doc);
        writer.close();
    
        //Open an IndexSearcher
        IndexReader reader = DirectoryReader.open(dir);
        IndexSearcher searcher = new IndexSearcher(reader);
    
        //Create a query
        QueryParser parser = new QueryParser("text", analyzer);
        Query query = parser.parse("world");
    
        //Search for results of the query in the index
        System.out.println("Searching for: \"" + query + "\"");
        TopDocs results = searcher.search(query, 10);
        for (ScoreDoc result : results.scoreDocs) {
            Document resultDoc = searcher.doc(result.doc);
            System.out.println("score: " + result.score + 
                    " -- text: " + resultDoc.get("text"));
        }
        reader.close();
    }
}
 

Setup

Lucene is a Java library. If you don't have a Java development environment set up already, see the Java documentation.

Download the latest version of Lucene from the Apache website, and unzip it.

Add the required jars to your classpath. The following jars will be required by many projects, including the Hello World example here:

• core/lucene-core-6.1.0.jar : Core Lucene functionality.
• core/analysis/common/lucene-analyzers-common-6.1.0.jar : Provides a variety of analyzers, including the ubiquitous StandardAnalyzer.
• queryparser/lucene-queryparser-6.1.0.jar : Provides the query parser.

Place the code in HelloLucene.java . Compile it with this command:

javac -classpath "core/*:queryparser/*" HelloLucene.java
 

And run it with this command:

java -classpath ".:core/*:queryparser/*" HelloLucene