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Lucene的学习及使用实验

实验一下Lucene是怎么使用的。

参考:http://www.importnew.com/12715.html (例子比较简单)

http://www.yiibai.com/lucene/lucene_first_application.html (例子比较复杂)

这里也有一个例子:http://www.tuicool.com/articles/aqIZNnE

我用的版本比较高,是6.2.1版本,文档查阅:

http://lucene.apache.org/core/6_2_1/core/index.html

 

首先在Intellij里面创建一个Maven项目。名字为lucene-demo。(主要参考 http://www.importnew.com/12715.html )

其中pom.xml如下:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.myapp</groupId>
    <artifactId>lucene-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.apache.lucene/lucene-core -->
        <dependency>
            <groupId>org.apache.lucene</groupId>
            <artifactId>lucene-core</artifactId>
            <version>6.2.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.lucene</groupId>
            <artifactId>lucene-queryparser</artifactId>
            <version>6.2.1</version>
        </dependency>
    </dependencies>


</project>

讲了一个package:com.myapp.lucene,里面class LuceneDemo,内容如下:

package com.myapp.lucene;

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.RAMDirectory;
import org.apache.lucene.store.Directory;

import java.io.IOException;

/**
 * Created by baidu on 16/10/20.
 */
public class LuceneDemo {
    // 0. Specify the analyzer for tokenizing text.
    // The same analyzer should be used for indexing and searching
    static StandardAnalyzer analyzer;
    static Directory index;

    static void prepareDoc() throws IOException{
        // 0. init analyzer
        analyzer = new StandardAnalyzer();

        // 1. create index
        index = new RAMDirectory();
        IndexWriterConfig config = new IndexWriterConfig(analyzer);

        IndexWriter w = new IndexWriter(index, config);

        addDoc(w, "lucence tutorial", "123456");
        addDoc(w, "hi hi hi", "222");
        addDoc(w, "ok LUCENCE", "123");
        w.close();
    }

    static void addDoc(IndexWriter w, String text, String more) throws IOException{
        Document doc = new Document();
        doc.add(new TextField("text", text, Field.Store.YES));
        doc.add(new StringField("more", more, Field.Store.YES));
        w.addDocument(doc);
    }

    static void search(String str) throws ParseException, IOException {
        // 2. query
        Query q = new QueryParser("text", analyzer).parse(str);

        // 3. search
        int listNum = 10;
        IndexReader reader = DirectoryReader.open(index);
        IndexSearcher searcher = new IndexSearcher(reader);
        TopScoreDocCollector collector = TopScoreDocCollector.create(listNum);
        searcher.search(q, collector);
        ScoreDoc[] hits = collector.topDocs().scoreDocs;

        // 4. display
        System.out.printf("Found %d docs.\n", hits.length);
        for (int i=0; i<hits.length; i++) {
            int docId = hits[i].doc;
            Document doc = searcher.doc(docId);
            System.out.printf("Doc %d: text: %s, more: %s\n", i+1, doc.get("text"), doc.get("more"));
        }
        reader.close();

    }

    public static void main(String[] args) {
        try {
            prepareDoc();
            search("Lucence");
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ParseException e) {
            e.printStackTrace();
        }

    }
}

然后运行,能够成功:

Found 2 docs.
Doc 1: text: lucence tutorial, more: 123456
Doc 2: text: ok LUCENCE, more: 123

Process finished with exit code 0

因为用的是RAMDirectory,所以应该没有创建实际的目录和文件。

另外,代码和逻辑中有几点需要注意的地方:

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。
编码过程中,报过好几次错,关于Exception需要wrap或者throws的情况。
有些API的版本升级了,参数和以前不一样。在实际的代码中根据实际要求有所修改。一般都是简化了。

 

Lucene的学习及使用实验