001package org.apache.turbine.services;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 *
012 *   http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022/**
023 * Interface for telling Turbine that the implementation class
024 * is an external service provider therefore can be used for looking
025 * up services not found by the Turbine implementation. It is
026 * assumed that the referenced service container handles the
027 * complete lifecycle of its services.
028 *
029 * @author <a href="mailto:siegfried.goeschl@it20one.at">Siegfried Goeschl</a>
030 */
031public interface TurbineServiceProvider
032{
033    /**
034     * Returns an instance of the requested service. If the
035     * given service is not available/found we throw a RuntimeException
036     * since this is less intrusive.
037     *
038     * @param roleName the name of the requested service
039     * @return an instance of the service
040     * @throws InstantiationException the service could not be instantiated
041     */
042    Object get(String roleName) throws InstantiationException;
043
044    /**
045     * Releases the instance you got before. This is only really
046     * required when not working with service singletons.
047     *
048     * @param component the component to release
049     */
050    void release(Object component);
051
052    /**
053     * Is the service known to the service container?
054     * @param roleName the name of the requested service
055     * @return true if the service is known to the provider
056     */
057    boolean exists(String roleName);
058}