src/java/org/apache/turbine/services/assemblerbroker/TurbineAssemblerBrokerService.java

package org.apache.turbine.services.assemblerbroker;

/* ====================================================================
 * 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 java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Vector;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.apache.turbine.modules.Assembler;
import org.apache.turbine.services.InitializationException;
import org.apache.turbine.services.TurbineBaseService;
import org.apache.turbine.services.assemblerbroker.util.AssemblerFactory;
import org.apache.turbine.util.TurbineException;

/**
 * TurbineAssemblerBrokerService allows assemblers (like screens,
 * actions and layouts) to be loaded from one or more AssemblerFactory
 * classes.  AssemblerFactory classes are registered with this broker
 * by adding them to the TurbineResources.properties file.
 *
 * @author <a href="mailto:leon@opticode.co.za">Leon Messerschmidt</a>
 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
 * @version $Id$
 */
public class TurbineAssemblerBrokerService
        extends TurbineBaseService
        implements AssemblerBrokerService
{
    /** Logging */
    private static Log log
            = LogFactory.getLog(TurbineAssemblerBrokerService.class);

    /** A structure that holds the registered AssemblerFactories */
    private Map factories = null;

    /**
     * Get a list of AssemblerFactories of a certain type
     *
     * @param type type of Assembler
     * @return list of AssemblerFactories
     */
    private List getFactoryGroup(String type)
    {
        if (!factories.containsKey(type))
        {
            factories.put(type, new Vector());
        }
        return (List) factories.get(type);
    }

    /**
     * Utiltiy method to register all factories for a given type.
     *
     * @param type type of Assembler
     * @throws TurbineException
     */
    private void registerFactories(String type)
        throws TurbineException
    {
        List names = getConfiguration().getList(type);

        log.info("Registering " + names.size() + " " + type + " factories.");

        for (Iterator it = names.iterator(); it.hasNext(); )
        {
            String factory = (String) it.next();
            try
            {
                Object o = Class.forName(factory).newInstance();
                registerFactory(type, (AssemblerFactory) o);
            }
            // these must be passed to the VM
            catch (ThreadDeath e)
            {
                throw e;
            }
            catch (OutOfMemoryError e)
            {
                throw e;
            }
            // when using Class.forName(), NoClassDefFoundErrors are likely
            // to happen (missing jar files)
            catch (Throwable t)
            {
                throw new TurbineException("Failed registering " + type
                        + " factory: " + factory, t);
            }
        }
    }

    /**
     * Initializes the AssemblerBroker and loads the AssemblerFactory
     * classes registered in TurbineResources.Properties.
     *
     * @throws InitializationException
     */
    public void init()
        throws InitializationException
    {
        factories = new HashMap();
        try
        {
            registerFactories(AssemblerBrokerService.ACTION_TYPE);
            registerFactories(AssemblerBrokerService.SCREEN_TYPE);
            registerFactories(AssemblerBrokerService.NAVIGATION_TYPE);
            registerFactories(AssemblerBrokerService.LAYOUT_TYPE);
            registerFactories(AssemblerBrokerService.PAGE_TYPE);
            registerFactories(AssemblerBrokerService.SCHEDULEDJOB_TYPE);
        }
        catch (TurbineException e)
        {
            throw new InitializationException(
                    "AssemblerBrokerService failed to initialize", e);
        }
        setInit(true);
    }

    /**
     * Register a new AssemblerFactory under a certain type
     *
     * @param type type of Assembler
     * @param factory factory to register
     */
    public void registerFactory(String type, AssemblerFactory factory)
    {
        getFactoryGroup(type).add(factory);
    }

    /**
     * Attempt to retrieve an Assembler of a given type with
     * a name.  Cycle through all the registered AssemblerFactory
     * classes of type and return the first non-null assembly
     * found.  If an assembly was not found return null.
     *
     * @param type type of Assembler
     * @param name name of the requested Assembler
     * @return an Assembler or null
     * @throws TurbineException
     */
    public Assembler getAssembler(String type, String name)
        throws TurbineException
    {
        List facs = getFactoryGroup(type);

        Assembler assembler = null;
        for (Iterator it = facs.iterator(); (assembler == null) && it.hasNext();)
        {
            AssemblerFactory fac = (AssemblerFactory) it.next();
            try
            {
                assembler = fac.getAssembler(name);
            }
            catch (Exception e)
            {
                throw new TurbineException("Failed to load an assembler for "
                                           + name + " from the " 
                                           + type + " factory "
                                           + fac.getClass().getName(), e);
            }
        }
        return assembler;
    }
}