Lucene 快速入门

摘要: Lucene使得全文索引这项技术活变得非常简单，我将用5分钟做个快速展示。

1.建立索引 这个例子展示的是在内存中为几个String建立索引

StandardAnalyzer analyzer = new StandardAnalyzer(Version.LUCENE_44);
Directory index = new RAMDirectory();

IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_44, analyzer);

IndexWriter w = new IndexWriter(index, config);
addDoc(w, "Lucene in Action", "193398817");
addDoc(w, "Lucene for Dummies", "55320055Z");
addDoc(w, "Managing Gigabytes", "55063554A");
addDoc(w, "The Art of Computer Science", "9900333X");
w.close();

来看addDoc()方法：

private static void addDoc(IndexWriter w, String title, String isbn) throws IOException {
Document doc = new Document();
doc.add(new TextField("title", title, Field.Store.YES));
doc.add(new StringField("isbn", isbn, Field.Store.YES));
w.addDocument(doc);
}

2.查询
从标准输入读取查询信息，建立Lucene的Query对象

String querystr = args.length > 0 ? args[0] : "lucene";
Query q = new QueryParser(Version.LUCENE_44, "title", analyzer).parse(querystr);

3.查找
利用2产生的Query对象建立Searcher对象在索引中查找

int hitsPerPage = 10;
IndexReader reader = IndexReader.open(index);
IndexSearcher searcher = new IndexSearcher(reader);
TopScoreDocCollector collector = TopScoreDocCollector.create(hitsPerPage, true);
searcher.search(q, collector);
ScoreDoc[] hits = collector.topDocs().scoreDocs;

4.显示
显示查找结果

System.out.println("找到 " + hits.length + " hits.");
for(int i=0;i<hits.length;++i) {
int docId = hits[i].doc;
Document d = searcher.doc(docId);
System.out.println((i + 1) + ". " + d.get("isbn") + "\t" + d.get("title"));
}

完整的Java代码：

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.queryparser.classic.ParseException;
import org.apache.lucene.queryparser.classic.QueryParser;
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.RAMDirectory;
import org.apache.lucene.util.Version;

import java.io.IOException;

public class HelloLucene {
public static void main(String[] args) throws IOException, ParseException {
// 0. analyzer
//
StandardAnalyzer analyzer = new StandardAnalyzer(Version.LUCENE_44);

// 1. index
Directory index = new RAMDirectory();

IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_44, analyzer);

IndexWriter w = new IndexWriter(index, config);
addDoc(w, "Lucene in Action", "193398817");
addDoc(w, "Lucene for Dummies", "55320055Z");
addDoc(w, "Managing Gigabytes", "55063554A");
addDoc(w, "The Art of Computer Science", "9900333X");
w.close();

// 2. query
String querystr = args.length > 0 ? args[0] : "lucene";

Query q = new QueryParser(Version.LUCENE_44, "title", analyzer).parse(querystr);

// 3. search
int hitsPerPage = 10;
IndexReader reader = DirectoryReader.open(index);
IndexSearcher searcher = new IndexSearcher(reader);
TopScoreDocCollector collector = TopScoreDocCollector.create(hitsPerPage, true);
searcher.search(q, collector);
ScoreDoc[] hits = collector.topDocs().scoreDocs;

// 4. display
System.out.println("找到 " + hits.length + " hits.");
for(int i=0;i<hits.length;++i) {
int docId = hits[i].doc;
Document d = searcher.doc(docId);
System.out.println((i + 1) + ". " + d.get("isbn") + "\t" + d.get("title"));
}

reader.close();
}

private static void addDoc(IndexWriter w, String title, String isbn) throws IOException {
Document doc = new Document();
doc.add(new TextField("title", title, Field.Store.YES));
doc.add(new StringField("isbn", isbn, Field.Store.YES));
w.addDocument(doc);
}
}