001// Copyright 2006, 2008, 2013 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.UsesMappedConfiguration; 018 019/** 020 * A provider of values for symbols, used by the {@link org.apache.tapestry5.ioc.services.SymbolSource} service. 021 * <p/> 022 * This is the service interface for the FactoryDefaults and ApplicationDefaults services; each of these takes a 023 * configuration mapping symbols to their values. 024 * 025 * @see FactoryDefaults 026 * @see ApplicationDefaults 027 */ 028@UsesMappedConfiguration(String.class) 029public interface SymbolProvider 030{ 031 /** 032 * Returns the value for the symbol, or null if this provider can not provide a value. The value itself may contain 033 * symbols that will be recursively expanded. 034 * 035 * @param symbolName 036 * @return the value or null 037 */ 038 String valueForSymbol(String symbolName); 039}