package org.apache.turbine.services.pool;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache Turbine" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Turbine", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import org.apache.turbine.services.Service;
import org.apache.turbine.util.TurbineException;

/**
 * The Pool Service extends the Factory Service by adding support
 * for pooling instantiated objects. When a new instance is
 * requested, the service first checks its pool if one is available.
 * If the the pool is empty, a new object will be instantiated
 * from the specified class. If only class name is given, the request
 * to create an intance will be forwarded to the Factory Service.
 *
 * <p>For objects implementing the Recyclable interface, a recycle
 * method will be called, when they are taken from the pool, and
 * a dispose method, when they are returned to the pool.
 *
 * @author <a href="mailto:ilkka.priha@simsoft.fi">Ilkka Priha</a>
 * @version $Id$
 */
public interface PoolService
        extends Service
{
    /** The key under which this service is stored in TurbineServices. */
    String SERVICE_NAME = "PoolService";
    
    /** The default pool capacity. */
    int DEFAULT_POOL_CAPACITY = 128;
    
    /** The name of the pool capacity property */
    String POOL_CAPACITY_KEY = "pool.capacity";
    
    /** Are we running in debug mode? */
    String POOL_DEBUG_KEY = "pool.debug";

    /** Default Value for debug mode */
    boolean POOL_DEBUG_DEFAULT = false;

    /**
     * Gets an instance of a named class.
     *
     * @param className the name of the class.
     * @return the instance.
     * @throws TurbineException if instantiation fails.
     */
    Object getInstance(String className)
            throws TurbineException;

    /**
     * Gets an instance of a named class using a specified class loader.
     *
     * <p>Class loaders are supported only if the isLoaderSupported
     * method returns true. Otherwise the loader parameter is ignored.
     *
     * @param className the name of the class.
     * @param loader the class loader.
     * @return the instance.
     * @throws TurbineException if instantiation fails.
     */
    Object getInstance(String className,
            ClassLoader loader)
            throws TurbineException;

    /**
     * Gets an instance of a named class.
     * Parameters for its constructor are given as an array of objects,
     * primitive types must be wrapped with a corresponding class.
     *
     * @param className the name of the class.
     * @param params an array containing the parameters of the constructor.
     * @param signature an array containing the signature of the constructor.
     * @return the instance.
     * @throws TurbineException if instantiation fails.
     */
    Object getInstance(String className,
            Object[] params,
            String[] signature)
            throws TurbineException;

    /**
     * Gets an instance of a named class using a specified class loader.
     * Parameters for its constructor are given as an array of objects,
     * primitive types must be wrapped with a corresponding class.
     *
     * <p>Class loaders are supported only if the isLoaderSupported
     * method returns true. Otherwise the loader parameter is ignored.
     *
     * @param className the name of the class.
     * @param loader the class loader.
     * @param params an array containing the parameters of the constructor.
     * @param signature an array containing the signature of the constructor.
     * @return the instance.
     * @throws TurbineException if instantiation fails.
     */
    Object getInstance(String className,
            ClassLoader loader,
            Object[] params,
            String[] signature)
            throws TurbineException;

    /**
     * Tests if specified class loaders are supported for a named class.
     *
     * @param className the name of the class.
     * @return true if class loaders are supported, false otherwise.
     * @throws TurbineException if test fails.
     * @deprecated Use TurbineFactory.isLoaderSupported(className)
     */
    boolean isLoaderSupported(String className)
            throws TurbineException;

    /**
     * Gets an instance of a specified class either from the pool
     * or by instatiating from the class if the pool is empty.
     *
     * @param clazz the class.
     * @return the instance.
     * @throws TurbineException if recycling fails.
     */
    Object getInstance(Class clazz)
            throws TurbineException;

    /**
     * Gets an instance of a specified class either from the pool
     * or by instatiating from the class if the pool is empty.
     *
     * @param clazz the class.
     * @param params an array containing the parameters of the constructor.
     * @param signature an array containing the signature of the constructor.
     * @return the instance.
     * @throws TurbineException if recycling fails.
     */
    Object getInstance(Class clazz,
            Object params[],
            String signature[])
            throws TurbineException;

    /**
     * Puts a used object back to the pool. Objects implementing
     * the Recyclable interface can provide a recycle method to
     * be called when they are reused and a dispose method to be
     * called when they are returned to the pool.
     *
     * @param instance the object instance to recycle.
     * @return true if the instance was accepted.
     */
    boolean putInstance(Object instance);

    /**
     * Gets the capacity of the pool for a named class.
     *
     * @param className the name of the class.
     */
    int getCapacity(String className);

    /**
     * Sets the capacity of the pool for a named class.
     * Note that the pool will be cleared after the change.
     *
     * @param className the name of the class.
     * @param capacity the new capacity.
     */
    void setCapacity(String className,
                     int capacity);

    /**
     * Gets the current size of the pool for a named class.
     *
     * @param className the name of the class.
     */
    int getSize(String className);

    /**
     * Clears instances of a named class from the pool.
     *
     * @param className the name of the class.
     */
    void clearPool(String className);

    /**
     * Clears all instances from the pool.
     */
    void clearPool();

}