Lucene in 5 minutes.

最新推荐文章于 2021-12-04 22:53:03 发布

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本文将介绍如何使用Lucene库在应用程序中轻松实现全文搜索功能。通过简单的步骤，包括创建索引、构建查询、搜索结果及显示结果，用户能在5分钟内掌握Lucene的基本应用。

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Lucene in 5 minutes

from LuceneTutorial.com

Now updated for Lucene 4.0!

Lucene makes it easy to add full-text search capability to your application. In fact, its so easy, I'm going to show you how in 5 minutes!

1. Index

For this simple case, we're going to create an in-memory index from some strings.

  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() is what actually adds documents to the index:

 
 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
 )
 ;
 
 
 }
 
  

Note the use of TextField for content we want tokenized, and StringField for id fields and the like, which we don't want tokenized.

2. Query

We read the query from stdin, parse it and build a lucene Query out of it.

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

3. Search

Using the Query we create a Searcher to search the index. Then a TopScoreDocCollector is instantiated to collect the top 10 scoring hits.

 
 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. Display

Now that we have results from our search, we display the results to the user.

 
 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"
 )
 )
 ;
 
 
 }
 
  

Here's the app in its entirety. Download HelloLucene.java

 
 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
 )
 ;
 
   
 }
 
 
 }