001/*
002 * HA-JDBC: High-Availability JDBC
003 * Copyright (c) 2004-2007 Paul Ferraro
004 * 
005 * This library is free software; you can redistribute it and/or modify it 
006 * under the terms of the GNU Lesser General Public License as published by the 
007 * Free Software Foundation; either version 2.1 of the License, or (at your 
008 * option) any later version.
009 * 
010 * This library is distributed in the hope that it will be useful, but WITHOUT
011 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 
012 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License 
013 * for more details.
014 * 
015 * You should have received a copy of the GNU Lesser General Public License
016 * along with this library; if not, write to the Free Software Foundation, 
017 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
018 * 
019 * Contact: ferraro@users.sourceforge.net
020 */
021package net.sf.hajdbc.distributable;
022
023import java.util.Arrays;
024import java.util.Collections;
025import java.util.Set;
026import java.util.TreeSet;
027
028import net.sf.hajdbc.DatabaseCluster;
029import net.sf.hajdbc.StateManager;
030import net.sf.hajdbc.util.Strings;
031
032/**
033 * @author Paul Ferraro
034 */
035public class QueryInitialStateCommand implements Command<Set<String>>
036{
037        private static final long serialVersionUID = -8409746321944635265L;
038
039        /**
040         * @see net.sf.hajdbc.distributable.Command#execute(net.sf.hajdbc.DatabaseCluster, net.sf.hajdbc.StateManager)
041         */
042        @Override
043        public <D> Set<String> execute(DatabaseCluster<D> databaseCluster, StateManager stateManager)
044        {
045                return databaseCluster.isActive() ? stateManager.getInitialState() : null;
046        }
047
048        /**
049         * Optimize transfer of result by marshalling set of strings into a string.
050         * @see net.sf.hajdbc.distributable.Command#marshalResult(java.lang.Object)
051         */
052        @Override
053        public Object marshalResult(Set<String> set)
054        {
055                return (set != null) ? Strings.join(set, Strings.COMMA) : null;
056        }
057
058        /**
059         * Restore marshalled string into a set of strings
060         * @see net.sf.hajdbc.distributable.Command#unmarshalResult(java.lang.Object)
061         */
062        @Override
063        public Set<String> unmarshalResult(Object object)
064        {
065                String state = (String) object;
066                
067                if (state == null) return null;
068                
069                if (state.length() == 0) return Collections.emptySet();
070                
071                return new TreeSet<String>(Arrays.asList(state.split(Strings.COMMA)));
072        }
073        
074        /**
075         * @see java.lang.Object#toString()
076         */
077        @Override
078        public String toString()
079        {
080                return this.getClass().getName();
081        }
082}