001    /*
002     * Cumulus4j - Securing your data in the cloud - http://cumulus4j.org
003     * Copyright (C) 2011 NightLabs Consulting GmbH
004     *
005     * This program is free software: you can redistribute it and/or modify
006     * it under the terms of the GNU Affero General Public License as
007     * published by the Free Software Foundation, either version 3 of the
008     * License, or (at your option) any later version.
009     *
010     * This program is distributed in the hope that it will be useful,
011     * but WITHOUT ANY WARRANTY; without even the implied warranty of
012     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
013     * GNU Affero General Public License for more details.
014     *
015     * You should have received a copy of the GNU Affero General Public License
016     * along with this program.  If not, see <http://www.gnu.org/licenses/>.
017     */
018    package org.cumulus4j.store.query.eval;
019    
020    import java.util.Collections;
021    import java.util.Set;
022    
023    import org.cumulus4j.store.query.QueryEvaluator;
024    import org.datanucleus.query.expression.VariableExpression;
025    import org.datanucleus.query.symbol.Symbol;
026    
027    /**
028     * Evaluator representing variables.
029     *
030     * @author Marco หงุ่ยตระกูล-Schulze - marco at nightlabs dot de
031     */
032    public class VariableExpressionEvaluator extends AbstractExpressionEvaluator<VariableExpression>
033    {
034            public VariableExpressionEvaluator(QueryEvaluator queryEvaluator, AbstractExpressionEvaluator<?> parent, VariableExpression expression)
035            {
036                    super(queryEvaluator, parent, expression);
037            }
038    
039            @Override
040            protected Set<Long> _queryResultDataEntryIDs(ResultDescriptor resultDescriptor)
041            {
042                    throw new UnsupportedOperationException("Cannot evaluate a variable without any context!");
043            }
044    
045            @Override
046            protected Set<Symbol> _getResultSymbols()
047            {
048                    Symbol symbol = getExpression().getSymbol();
049                    if (symbol == null)
050                            throw new IllegalStateException("getExpression().getSymbol() returned null!");
051    
052                    return Collections.singleton(symbol);
053            }
054    }