package org.apache.turbine.services;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/**
 * Interface for telling Turbine that the implementation class
 * is an external service provider therefore can be used for looking
 * up services not found by the Turbine implementation. It is
 * assumed that the referenced service container handles the
 * complete lifecycle of its services.
 *
 * @author <a href="mailto:siegfried.goeschl@it20one.at">Siegfried Goeschl</a>
 */
public interface TurbineServiceProvider
{
    /**
     * Returns an instance of the requested service. If the
     * given service is not available/found we throw a RuntimeException
     * since this is less intrusive.
     *
     * @param roleName the name of the requested service
     * @return an instance of the service
     * @throws InstantiationException the service could not be instantiated
     */
    Object get(String roleName) throws InstantiationException;

    /**
     * Releases the instance you got before. This is only really
     * required when not working with service singletons.
     *
     * @param component the component to release
     */
    void release(Object component);

    /**
     * Is the service known to the service container?
     * @param roleName the name of the requested service
     * @return true if the service is known to the provider
     */
    boolean exists(String roleName);
}
