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.engine;
016
017/**
018 *  A source for configuration properties.
019 *
020 *  @author Howard Lewis Ship
021 *  @since 2.3
022 *
023 **/
024
025public interface IPropertySource
026{
027    /**
028     *  Returns the value for a given property, or null if the
029     *  source does not provide a value for the named property.
030     *  Implementations of IPropertySource may use delegation
031     *  to resolve the value (that is, if one property source returns null,
032     *  it may forward the request to another source).
033     * 
034     **/
035    
036    public String getPropertyValue(String propertyName);
037}