001    /*
002     * Copyright 2006-2007 Stephen J. McConnell.
003     *
004     * Licensed  under the  Apache 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.apache.org/licenses/LICENSE-2.0
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
013     * implied.
014     *
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package net.dpml.util;
020    
021    /**
022     * Interace implemented by a value (key, ref, and property) resolver.
023     *
024     * @author <a href="http://www.dpml.net">Digital Product Management Library</a>
025     * @version 2.1.1
026     */
027    public interface Resolver
028    {
029       /**
030        * Return a property value.
031        * @param key the property key
032        * @return the property value
033        */
034        String getProperty( String key );
035        
036       /**
037        * Return a property value.
038        * @param key the property key
039        * @param value the default value
040        * @return the property value
041        */
042        String getProperty( String key, String value );
043        
044       /**
045        * Symbolic expansion of a supplied value.
046        * Replace any occurances of ${[key]} with the value of the property
047        * assigned to the [key] in system properties.
048        * @param value a string containing possibly multiple ${[value]} sequences
049        * @return the expanded string
050        */
051        String resolve( String value );
052    }