    001    // Copyright 2006, 2008 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.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    @UsesMappedConfiguration(String.class)
    026    public interface SymbolProvider
    027    {
    028        /**
    029         * Returns the value for the symbol, or null if this provider can not provide a value. The value itself may contain
    030         * symbols that will be recursively expanded.
    031         *
    032         * @param symbolName
    033         * @return the value or null
    034         */
    035        String valueForSymbol(String symbolName);
    036    }