/* Copyright (2006-2007) Schibsted Søk AS

  * This file is part of SESAT.

  *

  *   SESAT is free software: you can redistribute it and/or modify

  *   it under the terms of the GNU Affero General Public License as published by

  *   the Free Software Foundation, either version 3 of the License, or

  *   (at your option) any later version.

  *

  *   SESAT is distributed in the hope that it will be useful,

  *   but WITHOUT ANY WARRANTY; without even the implied warranty of

  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  *   GNU Affero General Public License for more details.

  *

  *   You should have received a copy of the GNU Affero General Public License

  *   along with SESAT.  If not, see <http://www.gnu.org/licenses/>.

  */

 package no.sesat.search.run;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 import no.sesat.search.site.SiteKeyedFactoryInstantiationException;

 import org.apache.log4j.Logger;

 /**

  * QueryFactory is part of no.sesat.search.query.

  *

  * Use QueryFactory to create a new RunningQuery instance. The RunningQuery

  * should contain all information on how to search in fast.

  *

  *

  * @version $Id: QueryFactory.java 6596 2008-05-10 10:05:48Z ssmiweve $

  */

 public abstract class QueryFactory {

     private static final Logger LOG = Logger.getLogger(QueryFactory.class);

     private static QueryFactory instance;

     /**

      * Create a new instance of QueryFactory.

      * @return instance

      */

     public static QueryFactory getInstance() {

         if (instance == null) {

             if (LOG.isInfoEnabled()) {

                 LOG.info("Creating new QueryFactory instance");

             }

             instance = new QueryFactoryImpl();

         }

         return instance;

     }

     /**

      * Create a new instance of running query. The implementation can

      * be RunningWebQuery, RunningAdvWebQuery for example.

      * @param mode with SearchConfiguration

      * @param request with parameters

      * @param response

      * @return instance of RunningQuery

      */

     public abstract RunningQuery createQuery(

                              RunningQuery.Context cxt,

                              HttpServletRequest request,

                              HttpServletResponse response) throws SiteKeyedFactoryInstantiationException;

 }