lucence入門

更新：下面的代碼使用Lucene 4.0版本！

Lucene大大簡化了在應用中集成全文搜索的功能。但實際上Lucene十分簡單，我可以在五分鐘之內向你展示如何使用Lucene。

1. 建立索引

爲了簡單起見，我們下面爲一些字符串創建內存索引：

1 2 3 4 5 6 7 8 9 10 11

StandardAnalyzer analyzer = newStandardAnalyzer(Version.LUCENE_40); Directory index = newRAMDirectory();   IndexWriterConfig config = newIndexWriterConfig(Version.LUCENE_40, analyzer);   IndexWriter w = newIndexWriter(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();

addDoc()方法把文檔（譯者注：這裏的文檔是Lucene中的Document類的實例）添加到索引中。

1 2 3 4 5 6

privatestatic void addDoc(IndexWriter w, String title, String isbn) throwsIOException {   Document doc = newDocument();   doc.add(newTextField("title", title, Field.Store.YES));   doc.add(newStringField("isbn", isbn, Field.Store.YES));   w.addDocument(doc); }

注意，對於需要分詞的內容我們使用TextField，對於像id這樣不需要分詞的內容我們使用StringField。

2.搜索請求

我們從標準輸入（stdin）中讀入搜索請求，然後對它進行解析，最後創建一個Lucene中的Query對象。

1 2	String querystr = args.length > 0? args[0] : "lucene"; Query q = newQueryParser(Version.LUCENE_40, "title", analyzer).parse(querystr);

3.搜索

我們創建一個Searcher對象並且使用上面創建的Query對象來進行搜索，匹配到的前10個結果封裝在TopScoreDocCollector對象裏返回。

1 2 3 4 5 6

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

4.展示

現在我們得到了搜索結果，我們需要想用戶展示它。

1 2 3 4 5 6

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

這裏是這個小應用的完整代碼。下載HelloLucene.java。

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76

importorg.apache.lucene.analysis.standard.StandardAnalyzer; importorg.apache.lucene.document.Document; importorg.apache.lucene.document.Field; importorg.apache.lucene.document.StringField; importorg.apache.lucene.document.TextField; importorg.apache.lucene.index.DirectoryReader; importorg.apache.lucene.index.IndexReader; importorg.apache.lucene.index.IndexWriter; importorg.apache.lucene.index.IndexWriterConfig; importorg.apache.lucene.queryparser.classic.ParseException; importorg.apache.lucene.queryparser.classic.QueryParser; importorg.apache.lucene.search.IndexSearcher; importorg.apache.lucene.search.Query; importorg.apache.lucene.search.ScoreDoc; importorg.apache.lucene.search.TopScoreDocCollector; importorg.apache.lucene.store.Directory; importorg.apache.lucene.store.RAMDirectory; importorg.apache.lucene.util.Version;   importjava.io.IOException;   publicclass HelloLucene {   publicstatic void main(String[] args) throwsIOException, ParseException {     // 0. Specify the analyzer for tokenizing text.     //    The same analyzer should be used for indexing and searching     StandardAnalyzer analyzer = newStandardAnalyzer(Version.LUCENE_40);       // 1. create the index     Directory index = newRAMDirectory();       IndexWriterConfig config = newIndexWriterConfig(Version.LUCENE_40, analyzer);       IndexWriter w = newIndexWriter(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";       // the "title" arg specifies the default field to use     // when no field is explicitly specified in the query.     Query q = newQueryParser(Version.LUCENE_40, "title", analyzer).parse(querystr);       // 3. search     inthitsPerPage = 10;     IndexReader reader = DirectoryReader.open(index);     IndexSearcher searcher = newIndexSearcher(reader);     TopScoreDocCollector collector = TopScoreDocCollector.create(hitsPerPage, true);     searcher.search(q, collector);     ScoreDoc[] hits = collector.topDocs().scoreDocs;           // 4. display results     System.out.println("Found " + hits.length + " hits.");     for(inti=0;i<hits.length;++i) {       intdocId = hits[i].doc;       Document d = searcher.doc(docId);       System.out.println((i + 1) + ". " + d.get("isbn") + "\t"+ d.get("title"));     }       // reader can only be closed when there     // is no need to access the documents any more.     reader.close();   }     privatestatic void addDoc(IndexWriter w, String title, String isbn) throwsIOException {     Document doc = newDocument();     doc.add(newTextField("title", title, Field.Store.YES));       // use a string field for isbn because we don't want it tokenized     doc.add(newStringField("isbn", isbn, Field.Store.YES));     w.addDocument(doc);   } }

可以直接在命令行中使用這個小應用，鍵入java HelloLucene 。