001package org.apache.turbine.services;
002
003
004/*
005 * Licensed to the Apache Software Foundation (ASF) under one
006 * or more contributor license agreements.  See the NOTICE file
007 * distributed with this work for additional information
008 * regarding copyright ownership.  The ASF licenses this file
009 * to you under the Apache License, Version 2.0 (the
010 * "License"); you may not use this file except in compliance
011 * with the License.  You may obtain a copy of the License at
012 *
013 *   http://www.apache.org/licenses/LICENSE-2.0
014 *
015 * Unless required by applicable law or agreed to in writing,
016 * software distributed under the License is distributed on an
017 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
018 * KIND, either express or implied.  See the License for the
019 * specific language governing permissions and limitations
020 * under the License.
021 */
022
023
024/**
025 * Classes that implement this interface can act as a broker for
026 * <code>Initable</code> classes.
027 *
028 * Functionality provided by the broker includes:
029 *
030 * <ul>
031 *
032 * <li>Maintaining a single instance of each <code>Initable</code> in
033 * the system.</li>
034 *
035 * <li>Early initialization of <code>Initables</code> during system
036 * startup.</li>
037 *
038 * <li>Late initialization of <code>Initables</code> before they are
039 * used.</li>
040 *
041 * <li>Providing instances of <code>Initables</code> to requesting
042 * parties.</li>
043 *
044 * <li>Maintaining dependencies between <code>Initables</code> during
045 * early initialization phases, including circular dependencies
046 * detection.</li>
047 *
048 * </ul>
049 *
050 * @author <a href="mailto:burton@apache.org">Kevin Burton</a>
051 * @author <a href="mailto:krzewski@e-point.pl">Rafal Krzewski</a>
052 * @version $Id$
053 */
054public interface InitableBroker
055{
056    /**
057     * Performs early initialization of an Initable class.
058     *
059     * If your class depends on another Initable being initialized to
060     * perform early initialization, you should always ask your broker
061     * to initialize the other class with the objects that are passed
062     * to you, before you try to retrieve that Initable's instance with
063     * getInitable().
064     *
065     * @param className The name of the class to be initialized.
066     * @param data An object to be used for initialization activities.
067     * @throws InitializationException if initialization of this
068     * class was not successful.
069     */
070    void initClass(String className, Object data)
071            throws InitializationException;
072
073    /**
074     * Shutdowns an Initable class.
075     *
076     * This method is used to release resources allocated by an
077     * Initable class, and return it to initial (uninitialized)
078     * state.
079     *
080     * @param className The name of the class to be uninitialized.
081     */
082    void shutdownClass(String className);
083
084    /**
085     * Provides an instance of Initable class ready to work.
086     *
087     * If the requested class couldn't be instatiated or initialized,
088     * InstantiationException will be thrown.  You needn't handle this
089     * exception in your code, since it indicates fatal
090     * misconfigurtion of the system.
091     *
092     * @param className The name of the Initable requested.
093     * @return An instance of requested Initable.
094     * @throws InstantiationException if there was a problem
095     * during instantiation or initialization of the Initable.
096     */
097    Initable getInitable(String className) throws InstantiationException;
098}