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package org.apache.turbine.services;

/*
 * Copyright 2001-2005 The Apache Software Foundation.
 *
 * Licensed 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.
 */

/**
 * Classes that implement this interface need initialization before
 * they can work.
 *
 * These classes rely also on an <code>InitableBroker</code> that
 * ensures that there is only one instance of the class in the system,
 * and handles dependencies between <code>Initables</code>.
 *
 * @author <a href="mailto:burton@apache.org">Kevin Burton</a>
 * @author <a href="mailto:krzewski@e-point.pl">Rafal Krzewski</a>
 * @version $Id: Initable.java 264148 2005-08-29 14:21:04Z henning $
 */
public interface Initable
{
    /**
     * Provides an Initable with a reference to the InitableBroker
     * that instantiated this object, so that it can access other
     * Initables.
     *
     * @param broker The InitableBroker that instantiated this object.
     */
    void setInitableBroker(InitableBroker broker);

    /**
     * Performs early initailization of an Initable
     *
     * During the startup of the system, different objects may be
     * passed to your class using this method.  It should ignore any
     * objects that it doesn't need or understand.
     *
     * After the class changes its internal state so that getInit()
     * returns true, this method will be called no more, and late
     * initialization will not be performed.
     *
     * If your class relies on early initialization, and the object it
     * expects was not received, you can use late initialization to
     * throw an exception and complain.
     *
     * @param data An Object to use for initialization activities.
     * @exception InitializationException if initilaization of this
     * class was not successful.
     */
    void init(Object data) throws InitializationException;

    /**
     * Performs late initialization of an Initable.
     *
     * When your class is being requested from an InitableBroker, it
     * will call getInit(), and if it returns false, this method will
     * be invoked.
     *
     * @exception InitializationException if initialization of this
     * class was not successful.
     */
    void init() throws InitializationException;

    /**
     * Returns an <code>Initable</code> to an uninitialized state.
     *
     * <p>This method must release all resources allocated by the
     * <code>Initable</code> implementation, and resetting its internal state.
     * You may chose to implement this operation or not. If you support
     * this operation, getInit() should return false after successful
     * shutdown of the service.
     */
    void shutdown();

    /**
     * Returns initialization status of an Initable.
     *
     * @return Initialization status of an Initable.
     */
    boolean getInit();
}
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