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
015package org.apache.hivemind.conditional;
016
017import 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 */
025public 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}