framework/src/com/primix/tapestry/ApplicationServlet.java

package com.primix.tapestry;

/*
 * Tapestry Web Application Framework
 * Copyright (c) 2000 by Howard Ship and Primix Solutions
 *
 * Primix Solutions
 * One Arsenal Marketplace
 * Watertown, MA 02472
 * http://www.primix.com
 * mailto:hship@primix.com
 * 
 * This library is free software.
 * 
 * You may redistribute it and/or modify it under the terms of the GNU
 * Lesser General Public License as published by the Free Software Foundation.
 *
 * Version 2.1 of the license should be included with this distribution in
 * the file LICENSE, as well as License.html. If the license is not
 * included    with this distribution, you may find a copy at the FSF web
 * site at 'www.gnu.org' or 'www.fsf.org', or you may write to the
 * Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139 USA.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 */

import javax.servlet.http.*;
import java.io.*;
import javax.servlet.*;

/**
 * Links a servlet container with a Tapestry application.
 *
 * <p>Subclasses provide the servlet with its application by implementing
 * the abstract method {@link #getApplication(RequestContext)}.
 *
 * <p>This class is derived from the original class 
 * <code>com.primix.servlet.GatewayServlet</code>
 * part of the <b>ServletUtils</b> framework available from
 * <a href="http://www.gjt.org/servlets/JCVSlet/list/gjt/com/primix/servlet">The Giant 
 * Java Tree</a>.
 *
 * @version $Id$
 * @author Howard Ship
 */

abstract public class ApplicationServlet extends HttpServlet
{

	/**
	* Handles the GET and POST requests. Performs the following:
	* <ul>
	* <li>Construct a {@link RequestContext}
	* <li>Invoke {@link #getApplication(RequestContext)} to get the {@link IApplication}
	* <li>Invoke {@link IApplication#service(RequestContext)} on the application
	* </ul>
	*/

	public void doGet(HttpServletRequest request, HttpServletResponse response) 
	throws IOException, ServletException
	{
		RequestContext context;
		IApplication application;

		// Create a context from the various bits and pieces.

		context = new RequestContext(this, request, response);

		try
		{

			// The subclass provides the delegate.

			application = getApplication(context);

			if (application == null)
				throw new ServletException(
					"Could not locate an application to service this request.");

			application.service(context);
		}
		catch (ServletException e)
		{
			log("ServletException", e);

			// Rethrow it.

			throw e;
		}
		catch (IOException e)
		{
			log("IOException", e);

			// Rethrow it.

			throw e;
		}
	}

	/**
	* Respond the same to a POST as to a GET.
	*/

	public void doPost(HttpServletRequest request, HttpServletResponse response) 
	throws IOException, ServletException
	{
		doGet(request, response);
	}

	/**
	* Invoked by 
	* {@link #doGet(HttpServletRequest, HttpServletResponse)}
	* to locate the {@link IApplication application} for the servlet.
	* This method should create the application, or locate it within the
	* {@link HttpSession}.
	*
	*/

	abstract protected IApplication getApplication(RequestContext context);
}