WebletsContextListener.java

/*
 * Copyright 2005 John R. Fallows
 *
 * 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.
 */
package net.java.dev.weblets;

import net.java.dev.weblets.util.ServiceLoader;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/**
 * The WebletContextListener is responsible for initializing the WebletContainer. so The
 * <code>META-INF/services/net.java.dev.weblets.WebletsContextListener</code> Service Provider configuration file is used to lookup the implementation class for
 * this ServletContextListener, as defined by the JAR file specification.
 */
public final class WebletsContextListener implements ServletContextListener {
	/**
	 * Callback when the ServletContext is initialized.
	 * 
	 * @param event
	 *            the servlet context event
	 */
	public void contextInitialized(ServletContextEvent event) {
		if (_WEBLETS_CONTEXT_LISTENER_CLASS == null)
			_WEBLETS_CONTEXT_LISTENER_CLASS = ServiceLoader.loadService(WebletsContextListener.class);
		try {
			_delegate = (ServletContextListener) _WEBLETS_CONTEXT_LISTENER_CLASS.newInstance();
		} catch (IllegalAccessException e) {
			throw new RuntimeException("Unable to access " + "WebletsContextListener implementation", e);
		} catch (InstantiationException e) {
			throw new RuntimeException("Unable to instantiate " + "WebletsContextListener implementation", e);
		}
		try {
			_delegate.contextInitialized(event);
		} catch (RuntimeException e) {
			System.err.println(e.toString());
			throw e;
		}
	}

	/**
	 * Callback when the ServletContext is destroyed.
	 * 
	 * @param event
	 *            the servlet context event
	 */
	public void contextDestroyed(ServletContextEvent event) {
		_delegate.contextDestroyed(event);
	}

	private ServletContextListener	_delegate;
	// the WebletsContextListener Service Provider implementation class
	static private Class			_WEBLETS_CONTEXT_LISTENER_CLASS;
}