Lucene example source code file (FormBasedXmlQueryDemo.java)

This example Lucene source code file (FormBasedXmlQueryDemo.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

bufferedreader, coreplusextensionsparser, document, document, field, field, http, indexwriter, io, ioexception, override, request, response, servlet, servletexception, servletexception, string, string, stringtokenizer, util

The Lucene FormBasedXmlQueryDemo.java source code

/**
 * 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.
 */

package org.apache.lucene.xmlparser.webdemo;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Enumeration;
import java.util.Properties;
import java.util.StringTokenizer;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.index.IndexWriter;
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.RAMDirectory;
import org.apache.lucene.xmlparser.CorePlusExtensionsParser;
import org.apache.lucene.xmlparser.QueryTemplateManager;

public class FormBasedXmlQueryDemo extends HttpServlet {

	private QueryTemplateManager queryTemplateManager;
	private CorePlusExtensionsParser xmlParser;
	private IndexSearcher searcher;
	private Analyzer analyzer=new StandardAnalyzer(org.apache.lucene.util.Version.LUCENE_CURRENT);

	@Override
	public void init(ServletConfig config) throws ServletException {
		super.init(config);
		try {
			openExampleIndex();

			//load servlet configuration settings
			String xslFile=config.getInitParameter("xslFile");
			String defaultStandardQueryParserField = config.getInitParameter("defaultStandardQueryParserField");


			//Load and cache choice of XSL query template using QueryTemplateManager
			queryTemplateManager=new QueryTemplateManager(
					getServletContext().getResourceAsStream("/WEB-INF/"+xslFile));

			//initialize an XML Query Parser for use by all threads
			xmlParser=new CorePlusExtensionsParser(defaultStandardQueryParserField,analyzer);
		} catch (Exception e) {
			throw new ServletException("Error loading query template",e);
		}
	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//Take all completed form fields and add to a Properties object
		Properties completedFormFields=new Properties();
		Enumeration pNames = request.getParameterNames();
		while(pNames.hasMoreElements()){
			String propName=(String) pNames.nextElement();
			String value=request.getParameter(propName);
			if((value!=null)&&(value.trim().length()>0)){
				completedFormFields.setProperty(propName, value);
			}
		}

		try{

			//Create an XML query by populating template with given user criteria
			org.w3c.dom.Document xmlQuery=queryTemplateManager.getQueryAsDOM(completedFormFields);

			//Parse the XML to produce a Lucene query
			Query query=xmlParser.getQuery(xmlQuery.getDocumentElement());

			//Run the query
			TopDocs topDocs = searcher.search(query,10);

			//and package the results and forward to JSP
			if(topDocs!=null)	{
				ScoreDoc[] sd = topDocs.scoreDocs;
				Document[] results=new Document[sd.length];
				for (int i = 0; i < results.length; i++) {
					results[i]=searcher.doc(sd[i].doc);
					request.setAttribute("results", results);
				}
			}
			RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/index.jsp");
			dispatcher.forward(request,response);
		}
		catch(Exception e){
			throw new ServletException("Error processing query",e);
		}
	}

	private void openExampleIndex() throws CorruptIndexException, IOException {

		//Create a RAM-based index from our test data file
		RAMDirectory rd=new RAMDirectory();
		IndexWriter writer=new IndexWriter (rd,analyzer,IndexWriter.MaxFieldLength.LIMITED);
		InputStream dataIn=getServletContext().getResourceAsStream("/WEB-INF/data.tsv");
		BufferedReader br = new BufferedReader(new InputStreamReader(dataIn));
		String line = br.readLine();
		while(line!=null)
		{
			line=line.trim();
			if(line.length()>0)
			{
				//parse row and create a document
				StringTokenizer st=new StringTokenizer(line,"\t");
				Document doc=new Document();
				doc.add(new Field("location",st.nextToken(),Field.Store.YES,
						Field.Index.ANALYZED_NO_NORMS));
				doc.add(new Field("salary",st.nextToken(),Field.Store.YES,
						Field.Index.ANALYZED_NO_NORMS));
				doc.add(new Field("type",st.nextToken(),Field.Store.YES,
						Field.Index.ANALYZED_NO_NORMS));
				doc.add(new Field("description",st.nextToken(),Field.Store.YES,
						Field.Index.ANALYZED));
				writer.addDocument(doc);
			}
			line=br.readLine();
		}
		writer.close();

		//open searcher
		searcher=new IndexSearcher(rd, true);
	}
}