全文检索Lucene (2)

接着全文检索Lucene (1) 。 下面我们来深入的研究一下，如何使用Lucene！

从全文检索Lucene (1)中我们可以看出，Lucene就好比一个双向的工作流，一方面是对索引库的维护，另一方面是对查询过程的支持。同时，这也是Lucene的优雅所在。

• • Lucene索引库构建分析
  • Lucene查询过程分析
  • 范例分析
    • Articlejava
    • LuceneUtilsjava
    • ArticleDocumentjava
    • ArticleIndexDaojava
    • 核心操作
  • 总结

---

Lucene索引库构建分析

Lucene查询过程分析

范例分析

下面我会写一个小的demo，大致的功能就是CRUD。类比JDBC，我们不可避免的要写一些工具类来优化我们的代码，减少重复代码。

Article.java

/**
 * @Date 2016年8月1日
 *
 * @author Administrator
 */
package domain;

/**
 * @author 郭瑞彪
 *
 */
public class Article {

    private Integer id;
    private String title;
    private String content;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    @Override
    public String toString() {
        return "Article [id=" + id + ", title=" + title + ", content=" + content + "]";
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

}

LuceneUtils.java

/**
 * @Date 2016年8月1日
 *
 * @author Administrator
 */
package util;

import java.io.IOException;
import java.nio.file.Paths;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
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.search.IndexSearcher;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;

/**
 * @author 郭瑞彪
 *
 */
public class LuceneUtils {

    private static Directory dir;

    public static Directory getDir() {
        return dir;
    }

    public static Analyzer getAnalyzer() {
        return analyzer;
    }

    private static Analyzer analyzer;

    /**
     * 获得一个用于操作索引库的IndexWriter对象
     *
     * @return
     */
    public static IndexWriter getIndexWriter() {
        try {
            Directory dir = FSDirectory.open(Paths.get("./indexDir/"));
            IndexWriterConfig indexWriterConfig = new IndexWriterConfig(new StandardAnalyzer());
            IndexWriter indexWriter = new IndexWriter(dir, indexWriterConfig);
            return indexWriter != null ? indexWriter : null;
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 获得一个索引库查询对象
     *
     * @return
     */
    public static IndexSearcher getIndexSearcher() {

        try {
            DirectoryReader directoryReader = DirectoryReader.open(FSDirectory.open(Paths.get("./indexDir/")));
            IndexReader indexReader = directoryReader;
            IndexSearcher indexSearcher = new IndexSearcher(indexReader);
            return indexSearcher != null ? indexSearcher : null;
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 释放IndexWriter资源
     *
     * @param indexWriter
     */
    public static void closeIndexWriter(IndexWriter indexWriter) {
        try {
            if (indexWriter != null) {
                indexWriter.close();
                indexWriter = null;
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    /**
     * 释放IndexSearcher资源
     *
     * @param indexSearcher
     */
    public static void closeIndexSearcher(IndexSearcher indexSearcher) {
        try {
            if (indexSearcher != null) {
                indexSearcher = null;
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

ArticleDocument.java

/**
 * @Date 2016年8月1日
 *
 * @author Administrator
 */
package util;

import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.Field.Store;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;

import domain.Article;

/**
 * @author 郭瑞彪
 *
 */
public class ArticleDocumentUtils {

    /**
     * Article转换成Licene的Document
     *
     * @param article
     * @return
     */
    public static Document article2Document(Article article) {
        Document doc = new Document();
        doc.add(new StringField("id", article.getId().toString(), Store.YES));
        doc.add(new TextField("title", article.getTitle(), Store.YES));
        doc.add(new TextField("content", article.getContent(), Store.YES));

        return doc != null ? doc : null;
    }

    /**
     * 将Document转换回Article
     *
     * @param document
     * @return
     */
    public static Article document2Article(Document document) {
        Article a = new Article();
        a.setId(Integer.parseInt(document.get("id")));
        a.setTitle(document.get("title"));
        a.setContent(document.get("content"));

        return a != null ? a : null;
    }

}

ArticleIndexDao.java

/**
 * @Date 2016年8月1日
 *
 * @author Administrator
 */
package dao;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.Term;
import org.apache.lucene.queryparser.classic.MultiFieldQueryParser;
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.TopDocs;
import org.apache.lucene.util.Version;

import domain.Article;
import domain.Page;
import util.ArticleDocumentUtils;
import util.LuceneUtils;

/**
 * @author 郭瑞彪
 *
 */
public class ArticleIndexDao {

    /**
     * 将新的数据保存到索引库
     *
     * @param article
     */
    public void save(Article article) {
        IndexWriter indexWriter = null;
        try {
            // 1. article --> document
            Document doc = ArticleDocumentUtils.article2Document(article);
            // 2. indexWriter.addDocument(document)
            indexWriter = LuceneUtils.getIndexWriter();
            indexWriter.addDocument(doc);
            // 临时代码
            indexWriter.close();
        } catch (IOException e) {
            throw new RuntimeException("ArticleIndexDao--save方法出错！\n" + e);
        } finally {
            LuceneUtils.closeIndexWriter(indexWriter);
        }
    }

    /**
     * 删除索引
     *
     * @param id
     */
    public void delete(Integer id) {
        IndexWriter indexWriter = null;
        try {
            indexWriter = LuceneUtils.getIndexWriter();
            indexWriter.deleteDocuments(new Term("id", id.toString()));
        } catch (IOException e) {
            throw new RuntimeException("ArticleIndexDao--save方法出错！\n" + e);
        } finally {
            LuceneUtils.closeIndexWriter(indexWriter);
        }
    }

    /**
     * 更新索引 <br>
     * 更新操作代价很高，一般采取先删除对应的索引，然后在创建这个索引的方式
     *
     * @param article
     */
    public void update(Article article) {
        IndexWriter indexWriter = null;
        try {
            Term term = new Term("id", article.getId().toString());
            indexWriter = LuceneUtils.getIndexWriter();
            // Document doc = new Document();
            // doc.add(new TextField("title", article.getTitle(), Store.YES));
            // doc.add(new TextField("content", article.getContent(),
            // Store.YES));
            // indexWriter.updateDocument(new Term("title", "content"), doc);

            // 优化版本的实现就是：先删除愿索引，然后再创建该索引
            indexWriter.deleteDocuments(term);
            Document doc = ArticleDocumentUtils.article2Document(article);
            indexWriter.addDocument(doc);
        } catch (IOException e) {
            throw new RuntimeException("ArticleIndexDao--save方法出错！\n" + e);
        } finally {
            LuceneUtils.closeIndexWriter(indexWriter);
        }
    }

    /**
     * 从索引库中查询
     *
     * @param queryString
     *            查询字符串
     * @return
     */
    public List<Article> search(String queryString) {
        try {
            // 1.queryString -->>Query
            String[] queryFields = new String[] { "title", "content" };
            Analyzer analyzer = new StandardAnalyzer();
            analyzer.setVersion(Version.LUCENE_6_0_0.LUCENE_6_1_0);
            QueryParser queryParser = new MultiFieldQueryParser(queryFields, analyzer);
            Query query = queryParser.parse(queryString);
            // 2. 查询，得到topDocs
            IndexSearcher indexSearcher = LuceneUtils.getIndexSearcher();
            TopDocs topDocs = indexSearcher.search(query, 100);
            // 3.处理结果并返回
            int totalHits = topDocs.totalHits;
            ScoreDoc[] scoreDocs = topDocs.scoreDocs;
            List<Article> articles = new ArrayList<Article>();
            for (int i = 0; i < scoreDocs.length; i++) {
                ScoreDoc scoreDoc = scoreDocs[i];
                Document doc = indexSearcher.doc(scoreDoc.doc);
                Article a = ArticleDocumentUtils.document2Article(doc);
                articles.add(a);
            }
            LuceneUtils.closeIndexSearcher(indexSearcher);
            return articles.size() > 0 ? articles : null;
        } catch (Exception e) {
            throw new RuntimeException("ArticleIndexDao-->> search方法出错！\n" + e);
        }
    }

}

核心操作

关键点：我们在update索引库的时候会花费很大的代价。官网上也建议“先删掉相关索引项，然后在新建这个索引项”。注意Term的使用格式即可。

总结

经JUnit测试，代码可以正常的通过。

当然，代码中可以进行优化的地方还有很多，但是作为演示来说还是差强人意的吧。

希望对于Lucene6.1.0版本有困难的小伙伴能从中收获到自己需要的内容。