tim@132: package de.intevation.gnv.geobackend.base.query;
tim@132: 
tim@132: import org.apache.log4j.Logger;
tim@132: 
tim@132: /**
tim@132:  * @author Tim Englich <tim.englich@intevation.de>
tim@132:  *
tim@132:  */
tim@132: public class QueryExecutorFactory {
sascha@541: 
sascha@541:     public static final String QUERY_EXECUTOR_FACTORY = "query.executor.factory";
sascha@885: 
tim@132:     /**
tim@132:      * the logger, used to log exceptions and additonaly information
tim@132:      */
tim@132:     private static Logger log = Logger.getLogger(QueryExecutorFactory.class);
tim@132: 
sascha@885: 
tim@132:     /**
tim@132:      * The singleton Instance of this Factory.
tim@132:      */
tim@132:     private static QueryExecutorFactory instance = null;
tim@132: 
tim@132:     /**
tim@132:      * Basic-Constructor of this Class
tim@132:      */
sascha@541:     public QueryExecutorFactory() {
tim@132:         super();
tim@132:     }
tim@132: 
tim@132:     /**
tim@132:      * This Method provides an singleton Instance of this Class.
tim@132:      * @return an singleton Instance of this Class
tim@132:      */
sascha@541:     public static synchronized QueryExecutorFactory getInstance(){
sascha@541:         if (instance == null) {
sascha@541:             String className = System.getProperty(QUERY_EXECUTOR_FACTORY);
sascha@541:             if (className != null) {
sascha@541:                 try {
sascha@541:                     Class clazz = Class.forName(className);
sascha@542:                     final QueryExecutorFactory factory =
sascha@542:                         (QueryExecutorFactory)clazz.newInstance();
sascha@542:                     Runtime.getRuntime().addShutdownHook(new Thread() {
tim@884:                         @Override
sascha@542:                         public void run() {
sascha@542:                             factory.shutdown();
sascha@542:                         }
sascha@542:                     });
sascha@542:                     return instance = factory;
sascha@541:                 }
sascha@541:                 catch (ClassNotFoundException cnfe) {
sascha@541:                     log.error(cnfe);
sascha@541:                 }
sascha@541:                 catch (InstantiationException ie) {
sascha@541:                     log.error(ie);
sascha@541:                 }
sascha@541:                 catch(IllegalAccessException iae) {
sascha@541:                     log.error(iae);
sascha@541:                 }
sascha@541:                 catch (ClassCastException cce) {
sascha@541:                     log.error(cce);
sascha@541:                 }
sascha@541:             }
sascha@541: 
tim@132:             instance = new QueryExecutorFactory();
tim@132:         }
tim@132:         return instance;
tim@132:     }
sascha@542: 
sascha@542:     public void shutdown() {
sascha@542:     }
sascha@885: 
tim@132:     /**
tim@132:      * Getting the QueryExecutor
tim@132:      * @return the QueryExecutor
tim@132:      */
tim@132:     public QueryExecutor getQueryExecutor(){
tim@132:         return new DefaultQueryExceutor();
tim@132:     }
tim@132: }