001// Licensed under the Apache License, Version 2.0 (the "License");
002// you may not use this file except in compliance with the License.
003// You may obtain a copy of the License at
004//
005//     http://www.apache.org/licenses/LICENSE-2.0
006//
007// Unless required by applicable law or agreed to in writing, software
008// distributed under the License is distributed on an "AS IS" BASIS,
009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
010// See the License for the specific language governing permissions and
011// limitations under the License.
012
013package org.apache.tapestry5.ioc.services;
014
015import org.apache.tapestry5.ioc.annotations.UsesOrderedConfiguration;
016import org.apache.tapestry5.ioc.annotations.Value;
017
018/**
019 * Used to manage <em>symbols</em>, configuration properties whose value is evaluated at runtime. Symbols use the Ant
020 * syntax: <code>${foo.bar.baz}</code> where <code>foo.bar.baz</code> is the name of the symbol. The symbol may appear
021 * inside some annotation, such as {@link Value}.
022 *
023 * The SymbolSource service configuration is an ordered list of {@link org.apache.tapestry5.ioc.services.SymbolProvider}s.
024 * Two key SymbolProvider services are FactoryDefaults and ApplicationDefaults.
025 */
026@UsesOrderedConfiguration(SymbolProvider.class)
027public interface SymbolSource
028{
029    /**
030     * Expands the value for a particular symbol. This may involve recursive expansion, if the immediate value for the
031     * symbol itself contains symbols.
032     *
033     * @param symbolName
034     * @return the expanded string
035     * @throws RuntimeException if the symbol name can not be expanded (no {@link SymbolProvider} can provide its
036     *                          value), or if an expansion is directly or indirectly recursive
037     */
038    String valueForSymbol(String symbolName);
039
040    /**
041     * Given an input string that <em>may</em> contain symbols, returns the string with any and all symbols fully
042     * expanded.
043     *
044     * @param input
045     * @return expanded input
046     */
047    String expandSymbols(String input);
048}