001    /**
002     * Copyright 2005-2012 The Kuali Foundation
003     *
004     * Licensed under the Educational Community License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.opensource.org/licenses/ecl2.php
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    package org.kuali.rice.krms.framework.engine.expression;
017    
018    import org.kuali.rice.krms.api.engine.ExecutionEnvironment;
019    import org.kuali.rice.krms.api.engine.IncompatibleTypeException;
020    
021    /**
022     * The {@link Expression} used in construction, will be invoked with the given {@link ExecutionEnvironment}.
023     *
024     * @author Kuali Rice Team (rice.collab@kuali.org)
025     *
026     */
027    public final class BooleanValidatingExpression implements Expression<Boolean> {
028    
029            private final Expression<? extends Object> expression;
030    
031        /**
032         * Constructor
033         * @param expression {@link Expression} to set the expression to
034         */
035            public BooleanValidatingExpression(Expression<? extends Object> expression) {
036                    this.expression = expression;
037            }
038    
039        @Override
040            public Boolean invoke(ExecutionEnvironment environment) {
041                    Object result = expression.invoke(environment);
042                    if (result instanceof Boolean) {
043                            return (Boolean)result;
044                    }
045                    throw new IncompatibleTypeException("Type mismatch when executing expression.", result, Boolean.class);
046            }
047            
048    }