natural.language.qa.LuceneSearch.java Source code

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Here is the source code for natural.language.qa.LuceneSearch.java

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package natural.language.qa;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.queryParser.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.search.highlight.DefaultEncoder;
import org.apache.lucene.search.highlight.Encoder;
import org.apache.lucene.search.highlight.Formatter;
import org.apache.lucene.search.highlight.Fragmenter;
import org.apache.lucene.search.highlight.Highlighter;
import org.apache.lucene.search.highlight.QueryScorer;
import org.apache.lucene.search.highlight.SimpleHTMLFormatter;
import org.apache.lucene.search.highlight.SimpleSpanFragmenter;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;

public class LuceneSearch {

    public List<LuceneSearchResult> search(String queryString, int maxRes) throws Exception {
        IndexSearcher searcher = null;
        List<LuceneSearchResult> results = new ArrayList<LuceneSearchResult>();
        try {
            Properties indexConf = new Properties();
            FileInputStream fis = new FileInputStream("index.properties");
            indexConf.load(fis);

            String index = indexConf.getProperty("index");
            String field = "contents";

            Directory indexDir = FSDirectory.open(new File(index));

            searcher = new IndexSearcher(indexDir);
            Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_31);

            QueryParser parser = new QueryParser(Version.LUCENE_31, field, analyzer);

            queryString = queryString.trim();
            if (queryString.length() == 0) {
                return results;
            }

            Query query = parser.parse(queryString);
            System.out.println("Searching for: " + query.toString(field));

            // ================================================
            Formatter f = new SimpleHTMLFormatter("", "");
            Encoder e = new DefaultEncoder();
            QueryScorer fs = new QueryScorer(query);
            Fragmenter fragmenter = new SimpleSpanFragmenter(fs, 50);// new SentenceFragmenter();
            Highlighter h = new Highlighter(f, e, fs);
            h.setTextFragmenter(fragmenter);
            h.setMaxDocCharsToAnalyze(Integer.MAX_VALUE);

            // ================================================

            // Collect docs
            TopDocs res = searcher.search(query, maxRes);
            int numTotalHits = res.totalHits;
            ScoreDoc[] scoreDocs = res.scoreDocs;

            for (ScoreDoc scoreDoc : scoreDocs) {
                Document doc = searcher.doc(scoreDoc.doc);
                String path = doc.get("path");
                String content = readDocument(path);
                String bestFragment = h.getBestFragment(analyzer, field, content);
                String frag = bestFragment;
                //System.out.println(frag);
                LuceneSearchResult hit = new LuceneSearchResult(scoreDoc.doc, path, frag);
                results.add(hit);
            }
            System.out.println(numTotalHits + " total matching documents");
        } finally {
            if (searcher != null) {
                searcher.close();
            }
        }
        return results;
    }

    private String readDocument(String path) throws Exception {
        StringBuffer strFileContents = new StringBuffer();
        BufferedReader reader = null;
        try {
            reader = new BufferedReader(new FileReader(path));
            String line = reader.readLine();
            while (line != null) {
                strFileContents.append(line).append("\n");
                line = reader.readLine();
            }
        } finally {
            if (reader != null) {
                reader.close();
            }
        }
        return strFileContents.toString();
    }

    public static void main(String[] args) throws Exception {
        LuceneSearch ls = new LuceneSearch();
        List<LuceneSearchResult> searchRes = ls.search("computer", 10);

        for (LuceneSearchResult res : searchRes) {
            System.out.println(
                    "============================[" + res.getDocId() + "]================================");
            System.out.println(res.getPath());
            System.out.println("------------------------------------------------------------");
            System.out.println(res.getContent());
        }
    }
}