Lucene 快速入门
Lucene大大简化了在应用中集成全文搜索的功能。但实际上Lucene十分简单,我可以在五分钟之内向你展示如何使用Lucene。
1. 建立索引
为了简单起见,我们下面为一些字符串创建内存索引:
StandardAnalyzer analyzer = new StandardAnalyzer(Version.LUCENE_40); Directory index = new RAMDirectory(); IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_40, 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();
addDoc()方法把文档(译者注:这里的文档是Lucene中的Document类的实例)添加到索引中。
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); }
注意,对于需要分词的内容我们使用TextField,对于像id这样不需要分词的内容我们使用StringField。
2.搜索请求
我们从标准输入(stdin)中读入搜索请求,然后对它进行解析,最后创建一个Lucene中的Query对象。
String querystr = args.length > 0 ? args[0] : "lucene"; Query q = new QueryParser(Version.LUCENE_40, "title", analyzer).parse(querystr);
3.搜索
我们创建一个Searcher对象并且使用上面创建的Query对象来进行搜索,匹配到的前10个结果封装在TopScoreDocCollector对象里返回。
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.展示
现在我们得到了搜索结果,我们需要想用户展示它。
System.out.println("Found " + 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")); }
完整代码如下:
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. Specify the analyzer for tokenizing text. // The same analyzer should be used for indexing and searching StandardAnalyzer analyzer = new StandardAnalyzer(Version.LUCENE_40); // 1. create the index Directory index = new RAMDirectory(); IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_40, 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"; // the "title" arg specifies the default field to use // when no field is explicitly specified in the query. Query q = new QueryParser(Version.LUCENE_40, "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 results System.out.println("Found " + 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 can only be closed when there // is no need to access the documents any more. 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)); // use a string field for isbn because we don't want it tokenized doc.add(new StringField("isbn", isbn, Field.Store.YES)); w.addDocument(doc); } }
posted on 2017-11-23 09:08 taich-flute 阅读(166) 评论(0) 编辑 收藏 举报