001    /*
002     * Copyright 2006 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    import java.net.URI;
022    import java.net.URISyntaxException;
023    
024    /**
025     * Interace implemented by a value (key, ref, and property) resolver.
026     *
027     * @author <a href="http://www.dpml.net">Digital Product Meta Library</a>
028     * @version 1.0.1
029     */
030    public interface Resolver
031    {
032       /**
033        * Utility function supporting resolution of uris containing 'resource' or 
034        * 'alias' schemes.  If the supplied uri scheme is 'resource' or 'alias' the 
035        * reference is resolved to a artifact type, group and name from which a 
036        * resource is resolved and the uri returned.  If the scheme is resource
037        * the usi of the resource is returned. If the scheme is 'alias' a 
038        * link alias is returned.  If the scheme is not 'resource' or 'alias' 
039        * the argument will be evaluated as a normal transit artifact uri 
040        * specification.
041        * 
042        * @param ref the uri argument
043        * @return the uri value
044        * @exception URISyntaxException if an error occurs during uri creation
045        */
046        URI toURI( String ref ) throws URISyntaxException;
047        
048       /**
049        * Return a property value.
050        * @param key the property key
051        * @return the property value
052        */
053        String getProperty( String key );
054        
055       /**
056        * Return a property value.
057        * @param key the property key
058        * @param value the default value
059        * @return the property value
060        */
061        String getProperty( String key, String value );
062        
063       /**
064        * Symbolic expansion of a supplied value.
065        * Replace any occurances of ${[key]} with the value of the property
066        * assigned to the [key] in system properties.
067        * @param value a string containing possibly multiple ${[value]} sequences
068        * @return the expanded string
069        */
070        String resolve( String value );
071    }