contextparamwebapplicationfactory.java

Wicket一个开发Java Web应用程序框架。它使得开发web应用程序变得容易而轻松。 Wicket利用一个POJO data beans组件使得它可以与任何持久层技术相结合。

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.wicket.protocol.http;

import org.apache.wicket.WicketRuntimeException;

/**
 * Factory that creates application objects based on the class name specified in the
 * {@link ContextParamWebApplicationFactory#APP_CLASS_PARAM} context variable.
 * 
 * @author Igor Vaynberg (ivaynberg)
 */
public class ContextParamWebApplicationFactory implements IWebApplicationFactory
{
	/**
	 * context parameter name that must contain the class name of the application
	 */
	public static final String APP_CLASS_PARAM = "applicationClassName";

	/** @see IWebApplicationFactory#createApplication(WicketFilter) */
	public WebApplication createApplication(WicketFilter filter)
	{
		final String applicationClassName = filter.getFilterConfig().getInitParameter(
				APP_CLASS_PARAM);

		if (applicationClassName == null)
		{
			throw new WicketRuntimeException(
					"servlet init param [" +
							APP_CLASS_PARAM +
							"] is missing. If you are trying to use your own implementation of IWebApplicationFactory and get this message then the servlet init param [" +
							WicketFilter.APP_FACT_PARAM + "] is missing");
		}

		return createApplication(applicationClassName);
	}

	/**
	 * Instantiates the application instance.
	 * 
	 * @param applicationClassName
	 *            the classname of the application to create
	 * @return the web application
	 */
	protected WebApplication createApplication(final String applicationClassName)
	{
		try
		{
			ClassLoader loader = Thread.currentThread().getContextClassLoader();
			if (loader == null)
			{
				loader = getClass().getClassLoader();
			}
			final Class applicationClass = loader.loadClass(applicationClassName);
			if (WebApplication.class.isAssignableFrom(applicationClass))
			{
				// Construct WebApplication subclass
				return (WebApplication)applicationClass.newInstance();
			}
			else
			{
				throw new WicketRuntimeException("Application class " + applicationClassName +
						" must be a subclass of WebApplication");
			}
		}
		catch (ClassNotFoundException e)
		{
			throw new WicketRuntimeException("Unable to create application of class " +
					applicationClassName, e);
		}
		catch (InstantiationException e)
		{
			throw new WicketRuntimeException("Unable to create application of class " +
					applicationClassName, e);
		}
		catch (IllegalAccessException e)
		{
			throw new WicketRuntimeException("Unable to create application of class " +
					applicationClassName, e);
		}
		catch (SecurityException e)
		{
			throw new WicketRuntimeException("Unable to create application of class " +
					applicationClassName, e);
		}
	}
}