    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}