Lucene五分钟教程
Lucene五分钟教程
更新:下面的代码使用Lucene 4.0版本!
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:
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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();
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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。
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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);
}
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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。
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String querystr = args.length > 0 ? args[ 0 ] : "lucene" ;
Query q = new QueryParser(Version.LUCENE_40, "title" , analyzer).parse(querystr);
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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。
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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;
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4.展示
现在我们得到了搜索结果,我们需要想用户展示它。
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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" ));
}
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这里是这个小应用的完整代码。下载HelloLucene.java。
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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);
}
}
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可以直接在命令行中使用这个小应用,键入java HelloLucene 。
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