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.tapestry.util;
016
017import org.apache.tapestry.engine.IPropertySource;
018
019/**
020 *  Obtain properties from JVM system properties.
021 * 
022 *
023 *  @author Howard Lewis Ship
024 *  @since 2.3
025 *
026 **/
027
028public class SystemPropertiesPropertySource implements IPropertySource
029{
030    private static IPropertySource _shared;
031    
032    public static synchronized IPropertySource getInstance()
033    {
034        if (_shared == null)
035            _shared = new SystemPropertiesPropertySource();
036            
037        return _shared; 
038    }
039
040    /**
041     *  Delegates to {@link System#getProperty(java.lang.String)}.
042     * 
043     **/
044    
045    public String getPropertyValue(String propertyName)
046    {
047        return System.getProperty(propertyName);
048    }
049
050}