package org.apache.turbine.modules;
/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2001 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/>.
*/
// Java Core Classes
import java.util.Vector;
// Turbine Utility Classes
import org.apache.turbine.TurbineConstants;
import org.apache.turbine.services.resources.TurbineResources;
import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService;
import org.apache.turbine.services.TurbineServices;
import org.apache.turbine.util.ObjectUtils;
import org.apache.turbine.util.RunData;
/**
* The purpose of this class is to allow one to load and execute
* Layout modules.
*
* @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>
* @version $Id$
*/
public class LayoutLoader extends GenericLoader
{
/** The single instance of this class. */
private static LayoutLoader instance = new LayoutLoader(
TurbineResources.getInt(TurbineConstants.LAYOUT_CACHE_SIZE, 10));
/**
* These ctor's are private to force clients to use getInstance()
* to access this class.
*/
private LayoutLoader()
{
super();
}
/**
* These ctor's are private to force clients to use getInstance()
* to access this class.
*/
private LayoutLoader(int i)
{
super(i);
}
/**
* Adds an instance of an object into the hashtable.
*
* @param name Name of object.
* @param layout Layout to be associated with name.
*/
private void addInstance( String name, Layout layout )
{
if ( cache() )
this.put( name, (Layout) layout );
}
/**
* Attempts to load and execute the external layout.
*
* @param data Turbine information.
* @param name Name of object that will execute the layout.
* @exception Exception a generic exception.
*/
public void exec( RunData data, String name )
throws Exception
{
// Execute layout
getInstance(name).build(data);
}
/**
* Pulls out an instance of the object by name. Name is just the
* single name of the object.
*
* @param name Name of object instance.
* @return A Layout with the specified name, or null.
* @exception Exception a generic exception.
*/
public Layout getInstance(String name)
throws Exception
{
Layout layout = null;
if ( cache() && this.containsKey( name ) )
{
layout = (Layout) this.get ( name );
}
else
{
// We get the broker service
AssemblerBrokerService ab =
(AssemblerBrokerService)TurbineServices.getInstance()
.getService (AssemblerBrokerService.SERVICE_NAME);
try
{
// Attempt to load the screen
layout = (Layout) ab.getAssembler(
AssemblerBrokerService.LAYOUT_TYPE,name);
}
catch (ClassCastException cce)
{
// This can alternatively let this exception be thrown
// So that the ClassCastException is shown in the
// browser window. Like this it shows "Screen not Found"
layout = null;
}
if (layout == null)
{
// If we did not find a screen we should try and give
// the user a reason for that...
// FIX ME: The AssemblerFactories should each add it's own
// string here...
Vector packages = TurbineResources.getVector(
TurbineConstants.MODULE_PACKAGES);
ObjectUtils.addOnce( packages,
GenericLoader.getBasePackage() );
throw new ClassNotFoundException(
"\n\n\tRequested Layout not found: " + name + "\n" +
"\tTurbine looked in the following modules.packages " +
"path: \n\t" + packages.toString() + "\n");
}
else if ( cache() )
{
// The new instance is added to the cache
addInstance( name, layout );
}
}
return layout;
}
/**
* The method through which this class is accessed.
*
* @return The single instance of this class.
*/
public static LayoutLoader getInstance()
{
return instance;
}
}