初识lucene
lucene的介绍网上有好多，再写一遍可能有点多余了。
使用lucene之前，有一系列的疑问
- 为什么lucene就比数据库快？
- 倒排索引是什么，他是怎么做到的
- lucene的数据结构是什么样的，cpu消耗，内存消耗主要因为什么
- lucene的索引流程以及查询流程是什么样的
推荐两篇文章，更进一步了解lucene
可以参考lucene与数据库对比部分
http://www.chedong.com/tech/lucene.html
可以参考第一篇和第二篇部分对lucene有一部分了解
http://blog.csdn.net/forfuture1978/article/details/5668956
《Lucene 原理与代码分析》看过一点，但是有点难度。
现在从《lucene实战》这本书来看，lucene使用的是4.7可能与3.0有所区别。
下面是第一节的例子
package com.mitchz.lucence;
import java.io.File;
import java.io.FileFilter;
import java.io.FileReader;
import java.io.IOException;
import org.apache.lucene.analysis.core.SimpleAnalyzer;
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.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;
/**
* @author mitchz
* @version 1.0
* @since 2014年4月30日
* @category com.mitchz.lucence
*/
public class Indexer
{
private IndexWriter writer;
public Indexer(String indexDir) throws IOException
{
Directory dir = FSDirectory.open(new File(indexDir));
IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_47,
new SimpleAnalyzer(Version.LUCENE_47));
writer = new IndexWriter(dir, config);
}
public int index(String dataDir, FileFilter filter) throws Exception
{
File[] files = (new File(dataDir)).listFiles();
for (File file : files)
{
if (!file.isDirectory() && !file.isHidden() && file.canRead()
&& (filter == null || filter.accept(file)))
{
indexFile(file);
}
}
return writer.numDocs();
}
private static class TextFilesFilter implements FileFilter
{
@Override
public boolean accept(File path)
{
return path.getName().toLowerCase().endsWith(".txt");
}
}
protected Document getDocument(File file) throws Exception
{
Document doc = new Document();
doc.add(new TextField("contents", new FileReader(file)));
doc.add(new StringField("filename", file.getName(), Field.Store.YES));
doc.add(new StringField("fullpath", file.getCanonicalPath(), Field.Store.YES));
return doc;
}
protected void indexFile(File file) throws Exception
{
System.out.println("Indexing " + file.getCanonicalPath());
Document doc = getDocument(file);
writer.addDocument(doc);
}
protected void close() throws IOException
{
writer.close();
}
public static void main(String[] args) throws Exception
{
if (args.length != 2)
{
throw new IllegalArgumentException("Usage java " + Indexer.class.getName()
+ "<index dir> <data dir>");
}
String indexDir = args[0];
String dataDir = args[1];
System.out.println("indexDir:" + indexDir);
System.out.println("dataDir:" + dataDir);
long start = System.currentTimeMillis();
Indexer indexer = new Indexer(indexDir);
int numIndexed;
try
{
numIndexed = indexer.index(dataDir, new TextFilesFilter());
}
finally
{
indexer.close();
}
long end = System.currentTimeMillis();
System.out.println("Indexing " + numIndexed + " files took " + (end - start)
+ " milliseconds");
}
}
package com.mitchz.lucence;
import java.io.File;
import java.io.IOException;
import org.apache.lucene.analysis.core.SimpleAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.DirectoryReader;
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.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;
/**
* @author mitchz
* @version 1.0
* @since 2014年4月30日
* @category com.mitchz.lucence
*/
public class Searcher
{
public static void main(String args[]) throws IOException, ParseException
{
if (args.length != 2)
{
throw new IllegalArgumentException("Usage java " + Searcher.class.getName()
+ "<index dir> <query>");
}
String indexDir = args[0];
String q = args[1];
search(indexDir, q);
}
public static void search(String indexDir, String q) throws IOException,
ParseException
{
Directory dir = FSDirectory.open(new File(indexDir));
DirectoryReader dirReader = DirectoryReader.open(dir);
IndexSearcher is = new IndexSearcher(dirReader);
QueryParser parser = new QueryParser(Version.LUCENE_47, "contents",
new SimpleAnalyzer(Version.LUCENE_47));
Query query = parser.parse(q);
long start = System.currentTimeMillis();
TopDocs hits = is.search(query, 10);
long end = System.currentTimeMillis();
System.out.println("Found " + hits.totalHits + " document(s) (in "
+ (end - start) + " milliseconds) that matched query '" + q + "':");
for (ScoreDoc scoreDoc : hits.scoreDocs)
{
Document doc = is.doc(scoreDoc.doc);
System.out.println(doc.get("filename"));
}
}
}
maven的配置如下：
<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.mitchz</groupId> <artifactId>lucence-test</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>lucence-test</name> <url>http://maven.apache.org</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> <dependency> <groupId>org.apache.lucene</groupId> <artifactId>lucene-core</artifactId> <version>4.7.0</version> </dependency> <dependency> <groupId>org.apache.lucene</groupId> <artifactId>lucene-analyzers-common</artifactId> <version>4.7.0</version> </dependency> <dependency> <groupId>org.apache.lucene</groupId> <artifactId>lucene-queryparser</artifactId> <version>4.7.0</version> </dependency> </dependencies> </project>
