Lucene初识

╰+攻爆jí腚メ 2022-05-16 23:26 203阅读 0赞

**目录**

Lucene简介

pom.xml:

lucene建立索引：

lucene的几种检索方式：

--------------------

# Lucene简介 #

[https://baike.baidu.com/item/Lucene/6753302][https_baike.baidu.com_item_Lucene_6753302]

简单来说，Lucene是一个用来检索的开源框架。

lucene检索需要的jar包：

# pom.xml: #

<dependencies>
      
        <dependency>
    	    <groupId>org.apache.lucene</groupId>
    	    <artifactId>lucene-core</artifactId>
    	    <version>7.4.0</version>
        </dependency>
        
        <dependency>
    	    <groupId>org.apache.lucene</groupId>
    	    <artifactId>lucene-queryparser</artifactId>
            <version>7.4.0</version>
        </dependency>
        
        <dependency>
    	    <groupId>org.apache.lucene</groupId>
    	    <artifactId>lucene-analyzers-common</artifactId>
    	    <version>7.4.0</version>
        </dependency>
      </dependencies>

# lucene建立索引： #

写了一个Junit测试类：

import java.nio.file.Paths;
    
    import org.apache.lucene.analysis.Analyzer;
    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.index.Term;
    import org.apache.lucene.store.Directory;
    import org.apache.lucene.store.FSDirectory;
    import org.junit.Before;
    import org.junit.Test;
            /*
                lucene测试类
               */
    public class IndexingTest {
    
    	private String ids[]={"1","2","3"};
    	private String citys[]={"qingdao","nanjing","shanghai"};
    	private String descs[]={
    			"Qingdao is a beautiful city.",
    			"Nanjing is a city of culture.",
    			"Shanghai is a bustling city."
    	};
    	
    	private Directory dir;
    	
    	@Before
    	public void setUp() throws Exception {
    		dir=FSDirectory.open(Paths.get("D:\\lucene2"));
    		IndexWriter writer=getWriter();
    		for(int i=0;i<ids.length;i++) {
    			Document doc=new Document();
    			doc.add(new StringField("id",ids[i], Field.Store.YES));
    			doc.add(new StringField("city",citys[i],Field.Store.YES));
    			doc.add(new TextField("desc",descs[i],Field.Store.NO));
    			writer.addDocument(doc);
    		}
    		writer.close();
    	}
    	
    	
    	/**
    	 * 获取IndexWriter实例
    	 */
    	private IndexWriter getWriter()throws Exception{
    		
    		Analyzer analyzer=new StandardAnalyzer();
    		IndexWriterConfig iwc=new IndexWriterConfig(analyzer);
    		IndexWriter writer=new IndexWriter(dir, iwc);
    		return writer;
    	}
    
    	/**
    	 * 测试写了几个文档
    	 * @throws Exception
    	 */
    	@Test
    	public void testIndexWriter()throws Exception{
    		 IndexWriter writer=getWriter();
    		 System.out.println("写入了"+writer.numDocs()+"个文档");
    		 writer.close();
    	}
    	
    	/**
    	 * 测试读取文档实例
    	 */
    	@Test
    	public void testIndexReader()throws Exception{
    		IndexReader reader=DirectoryReader.open(dir);
    		System.out.println("最大文档数:"+reader.maxDoc());
    		System.out.println("实际文档数:"+reader.numDocs());
    		reader.close();
    	}
    	
    	/**
    	 * 测试删除，在合并之前
    	 * 
    	 */
    	@Test
    	public void testDeleteBeforeMerge()throws Exception{
    		IndexWriter writer=getWriter();
    		System.out.println("删除之前的文档数量："+writer.numDocs());
    		writer.deleteDocuments(new Term("id","1"));
    		writer.commit();
    		System.out.println("writer.numDocs:"+writer.numDocs());
    		System.out.println("writer.maxDocs:"+writer.maxDoc());
    		writer.close();
    	}
    	
    	/**
    	 * 测试删除，在合并之后
    	 */
    	@Test
    	public void testDeleteAfterMerge()throws Exception{
    		IndexWriter writer=getWriter();
    		System.out.println("删除之前的文档数量："+writer.numDocs());
    		writer.deleteDocuments(new Term("id","1"));
    		writer.forceMergeDeletes();  //强制删除
    		writer.commit();
    		System.out.println("writer.numDocs:"+writer.numDocs());
    		System.out.println("writer.maxDocs:"+writer.maxDoc());
    		writer.close();
    	}
    	
    	/**
    	 * 测试更新
    	 */
    	@Test
    	public void testUpdate()throws Exception{
    		
    		IndexWriter writer=getWriter();
    		Document doc=new Document();
    		doc.add(new StringField("id","1",Field.Store.YES));
    		doc.add(new StringField("city","qingdao",Field.Store.YES));
    		doc.add(new TextField("desc","ddd is a city",Field.Store.NO));
    		writer.updateDocument(new Term("id","1"), doc);
    		writer.close();
    	}
    }

结果:

![70][]

# lucene的几种检索方式： #

[https_baike.baidu.com_item_Lucene_6753302]: https://baike.baidu.com/item/Lucene/6753302
[70]: /images/20220517/43ef9743325d41949dce461e0081a128.png