Mikel
为自己的系统搞个全文搜索
在本文我又提到lucene了，在java业界，提到全文检索，几乎没有什么人不知道它。
用google搜索一下，满世界都是有关资料。具有代表性的就是车东的“基于Java的全
文索引引擎Lucene简介”，我要写的也就只有最简单的三板斧，再加上支持中文的
ChineseAnalyzer以及按照时间排序的搜索结果排序方法。这些都可以在其他地方找
到相关资料，我只是把他们提出来，作为lucence应用中经常遇到的麻烦解决办法。
去年MSN上面有个朋友跟我提到希望用lucene构建个网站的全文检索，我当时就觉得
很简单，直说没问题没问题，不过他提到一个要求就是搜索结果要安装时间排序，
我查阅了些资料，发现lucene并不提供用户自定义排序方式，而只能按照自己相关
性算法排序。后来我在车东的weblucene项目找到了IndexOrderSearcher。解决了结
果排序常规需求。IndexOrderSearcher跟一般IndexSearch使用差不多，仅仅在构建
对象的时候多加一个参数IndexOrderSearcher.ORDER_BY_DOCID_DESC
IndexOrderSearcher indexsearcher =
new IndexOrderSearcher("/home/lucenetest/index",IndexOrderSearcher.ORDER_BY_DOCID_DESC);
新版本的lucene还提供了一个MultiFieldQueryParser，可以同时检索多个字段，以前
QueryParser比较麻烦。
private static ChineseAnalyzer chineseAnalyzer = new ChineseAnalyzer();
public Hits search(String queryText)
{
if (queryText == null)
{
return null;
}
Query query;
try
{
query = MultiFieldQueryParser.parse(queryText, new String[]{"title"},chineseAnalyzer);
return indexsearcher.search(query);
}
catch(Exception e)
{
return null;
}
}
下面是构建索引，定时从数据库取出数据索引，做完记录完成时间，我是把时间写入一个txt文件。
package com.test.search;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.cn.*;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.*;
import org.apache.lucene.index.*;
import java.io.*;
import java.SQL.*;
import java.util.Date;
import com.test.db.*;
import com.test.utility.*;
/**
* Title: SearchIndexer
* Description: 全文索引
* Copyright: Copyright (c) 2001
* Company: test
* @author Sean
* @version 1.0
*/
public class SearchIndexer
{
private String indexPath = null;
protected Analyzer analyzer = new ChineseAnalyzer();
public SearchIndexer(String s)
{
this.indexPath = s;
}
/**
* 索引某日期以前的所有文档
* @param fromdate
* @return
*/
public final void updateIndex(String fromdate)
{
Connection conn = DbUtil.getCon();
IndexWriter indexWriter = null;
try
{
indexWriter = getWriter(false);
//索引发布系统内部文件
PreparedStatement pstm = conn.prepareStatement(
"select title,body,creationtime from document
where creationtime > '" + fromdate +
"' order by creationtime");
ResultSet rs = pstm.executeQuery();
while (rs.next())
{
String creationtime = rs.getString("creationtime");
String title = rs.getString("title");
String body = rs.getString("body");
if (title == null || body == null)
{
continue;
}
try
{
addDocsToIndex(title,body, creationtime,indexWriter);
}
catch (Exception ex)
{
ex.printStackTrace();
}
}
indexWriter.optimize();
}
catch (Exception ex)
{
ex.printStackTrace();
}
finally
{
try
{
indexWriter.close();
conn.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
/**
* 检查索引文件是否存在
* @param s
* @return 索引是否存在
*/
private boolean indexExists(String s)
{
File file = new File(s + File.separator + "segments");
return file.exists();
}
/**
* 增加一组索引
* @param title
* @param body
* @param creationtime
* @param indexwriter
* @return
*/
private final void addNewsToIndex(String docid, String url,String title, String body,
String ptime, IndexWriter indexwriter) throws IOException
{
if (indexwriter == null)
{
return;
}
else
{
try
{
Document document = new Document();
document.add(Field.Text("title", title));
document.add(Field.Text("body", body));
document.add(new Field("creationtime", creationtime, true, true, false));
indexwriter.addDocument(document);
}
catch (Exception ex)
{
ex.printStackTrace();
}
return;
}
}
/**
* 取得IndexWriter
* @param flag 是否新建索引
* @return IndexWriter
*/
private IndexWriter getWriter(boolean flag) throws IOException
{
String s = indexPath;
if (s == null)
{
throw new IOException("索引文件路径设置错误.");
}
indexPath = s + File.separator + "search";
IndexWriter indexwriter = null;
if (flag)
{
try
{
indexwriter = new IndexWriter(indexPath, analyzer, true);
}
catch (Exception exception)
{
System.err.println("ERROR: Failed to create a new index writer.");
exception.printStackTrace();
}
}
else
{
if (indexExists(indexPath))
{
try
{
indexwriter = new IndexWriter(indexPath, analyzer, false);
}
catch (Exception exception1)
{
System.err.println("ERROR: Failed to open an index writer.");
exception1.printStackTrace();
}
}
else
{
try {
indexwriter = new IndexWriter(indexPath, analyzer, true);
}
catch (Exception exception2)
{
System.err.println("ERROR: Failed to create a new index writer.");
exception2.printStackTrace();
}
}
}
return indexwriter;
}
public static void main(String[] args)
{
String lastUpdate = "/home/lucenetest/lastUpdate.txt";
SearchIndexer searchIndexer = new SearchIndexer("/home/lucenetest/index");
//取出上次更新时间
String str = Util.readTxtFile(lastUpdate);
if(str==null || str.length()==0)
{
str = new java.util.Date().toString();
}
searchIndexer.updateIndex(str);
//写入当前时间
Util.writeTxtFile(lastUpdate,new java.util.Date(),false);
}
}
写个cmd或者sh在相应操作系统下面定时执行SearchIndexer就可以了
