001    // Copyright 2004, 2005 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.hivemind.conditional;
016    
017    import org.apache.hivemind.util.Defense;
018    
019    /**
020     * Evaluates a system property and returns true if its value is true.
021     * 
022     * @author Howard M. Lewis Ship
023     * @since 1.1
024     */
025    public class PropertyEvaluator implements Evaluator
026    {
027        private String _propertyName;
028    
029        public PropertyEvaluator(String propertyName)
030        {
031            Defense.notNull(propertyName, "propertyName");
032    
033            _propertyName = propertyName;
034        }
035    
036        // For testing
037    
038        String getPropertyName()
039        {
040            return _propertyName;
041        }
042    
043        /**
044         * Invokes {@link org.apache.hivemind.conditional.EvaluationContext#isPropertySet(String)}.
045         */
046        public boolean evaluate(EvaluationContext context, Node node)
047        {
048            return context.isPropertySet(_propertyName);
049        }
050    
051    }