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
015package org.apache.tapestry5.ioc.services;
016
017import org.apache.tapestry5.ioc.annotations.UsesOrderedConfiguration;
018import 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)
029public 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}