第六步：Lucene查询索引（优化一）

package cn.harmel.lucene;

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.document.Document;
import org.apache.lucene.queryparser.classic.ParseException;
import org.apache.lucene.queryparser.classic.QueryParser;
import org.apache.lucene.queryparser.classic.QueryParser.Operator;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.SearcherFactory;
import org.apache.lucene.search.SearcherManager;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.search.SortField.Type;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.FSDirectory;

public class SearchIndex {
	public static void main(String[] args) throws IOException, ParseException {
		/*---------------------------------------------------------------------------------
		 * String queryString="title:\"美国\"";//包含“美国”
		 * String queryString="NOT title:\"美国\" AND title:\"国\"";//不包含 “美国” 但是包含 “国”
		 * String queryString="title:\"中\" AND title:\"国人\"";//即包含 “中” 又包含 ”国人“
		 * String queryString="title:\"张三\" OR title:\"李四\"";//包含 “张三” 或 ”李四“
		 * String queryString="id:[1 TO 5]";//查询 1<=id<=5
		 * String queryString="id:{1 TO 5}";//查询 1<id<5
		 * String queryString="title:\"中国\" AND NOT title:\"张三\" AND id:[1 TO 5]";
		 * String queryString="title:(中国 张三)";即包含 “中国” 又包含 ”张三“
		 ---------------------------------------------------------------------------------*/
		String queryString="title:\"中国\"";

		Analyzer analyzer = new StandardAnalyzer();  //StandardAnalyzer:汉字一个一个字拆分索引
        IndexSearcher is = getIndexSearcher();
        QueryParser parser=new QueryParser("", analyzer);
        parser.setDefaultOperator(Operator.AND);//默认状态下，空格被认为是OR的关系，设置为空格为AND
        Query query = parser.parse(queryString);
        //排序
        Sort sort = new Sort(new SortField("dt", Type.LONG, true));
        TopDocs topDocs = is.search(query, 20,sort);
        System.out.println("总共匹配多少个：" + topDocs.totalHits);
        //获取查询结果集
        ScoreDoc[] hits = topDocs.scoreDocs;
        //遍历结果集
        for (ScoreDoc scoreDoc : hits) {
            Document document = is.doc(scoreDoc.doc);
            System.out.println(document.get("id")+"-"+document.get("name")+"-"+document.get("dt")+"-"+document.get("title"));
        }
        closeIndexSearcher(is);
	}	

	/*
	 * 解决：实现实时搜索功能
	 * 解决：在读取索引文件内容时，索引文件的打开操作IndexSearcher是个非常耗时耗资源的操作
	 * */
	private static byte[] synchronized_r = new byte[0];
	private static SearcherManager searcherManager = null;
	private static IndexSearcher getIndexSearcher() throws IOException {
	    IndexSearcher indexSearcher = null;
	    //保证在同一时刻最多只有一个线程执行该段代码
	    synchronized (synchronized_r) {
	        if(searcherManager == null) {
	            searcherManager = new SearcherManager(FSDirectory.open(Paths.get("E:\\LuceneIndex")), new SearcherFactory());
	        }
	        /*
	         * 这个方法同DirectoryReader.openIfChanged(dirReader)效果一样，其实底层还是调用的该方法实现的
	         * DirectoryReader.openIfChanged(dirReader)可以判断当前Reader对象的索引有没有被修改过
	         * 如果索引文件被更新过则重新加载该索引目录
	         * 但是这个时候的重新加载则比单纯的open(indexPath)要高效很多
	         * 它只是重新加载被更新过的文档，而单纯的open则是加载全部的文档
	         * */
	        searcherManager.maybeRefresh();
	        //借用一个IndexSearcher对象的引用，记住该对象用完之后要归还的，有借有还再借不难
	        indexSearcher = searcherManager.acquire();
	    }
	    return indexSearcher;
	}

	private static void closeIndexSearcher(IndexSearcher indexSearcher) throws IOException {
	    if(indexSearcher != null) {
	        searcherManager.release(indexSearcher);//归还从SearcherManager处借来的IndexSearcher对象
	    }
	    indexSearcher = null;
	}
}