001    // Copyright 2006, 2007, 2008, 2010 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    
015    package org.apache.tapestry5.ioc.services;
016    
017    import org.apache.tapestry5.ioc.annotations.UsesOrderedConfiguration;
018    import org.apache.tapestry5.ioc.annotations.Value;
019    
020    /**
021     * Used to manage <em>symbols</em>, configuration properties whose value is evaluated at runtime. Symbols use the Ant
022     * syntax: <code>${foo.bar.baz}</code> where <code>foo.bar.baz</code> is the name of the symbol. The symbol may appear
023     * inside some annotation, such as {@link Value}.
024     * <p/>
025     * The SymbolSource service configuration is an ordered list of {@link org.apache.tapestry5.ioc.services.SymbolProvider}s.
026     * Two key SymbolProvider services are FactoryDefaults and ApplicationDefaults.
027     */
028    @UsesOrderedConfiguration(SymbolProvider.class)
029    public interface SymbolSource
030    {
031        /**
032         * Expands the value for a particular symbol. This may involve recursive expansion, if the immediate value for the
033         * symbol itself contains symbols.
034         *
035         * @param symbolName
036         * @return the expanded string
037         * @throws RuntimeException if the symbol name can not be expanded (no {@link SymbolProvider} can provide its
038         *                          value), or if an expansion is directly or indirectly recursive
039         */
040        String valueForSymbol(String symbolName);
041    
042        /**
043         * Given an input string that <em>may</em> contain symbols, returns the string with any and all symbols fully
044         * expanded.
045         *
046         * @param input
047         * @return expanded input
048         */
049        String expandSymbols(String input);
050    }