    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    }