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Wicket is a Java web application framework that takes simplicity, separation of concerns and ease of development to a whole new level. Wicket pages can be mocked up, previewed and later revised using standard WYSIWYG HTML design tools. Dynamic content processing and form handling is all handled in Java code using a first-class component model backed by POJO data beans that can easily be persisted using your favorite technology.

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/*
 * 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;

import org.apache.wicket.request.cycle.RequestCycle;

/**
 * Holds thread local state for Wicket data.
 * 
 * @author Matej Knopp
 */
public class ThreadContext
{
	private Application application;

	private RequestCycle requestCycle;

	private Session session;

	private static final ThreadLocal threadLocal = new ThreadLocal();

	/**
	 * INTERNAL METHOD
	 * 
	 * @param createIfDoesNotExist
	 * @return ThreadContext
	 */
	public static ThreadContext get(boolean createIfDoesNotExist)
	{
		ThreadContext context = threadLocal.get();
		if (context == null)
		{
			if (createIfDoesNotExist)
			{
				context = new ThreadContext();
				threadLocal.set(context);
			}
			else
			{
				/*
				 * There is no ThreadContext set, but the threadLocal.get() operation has registered
				 * registered the threadLocal in this Thread's ThreadLocal map. We must now remove it.
				 */
				threadLocal.remove();
			}
		}
		return context;
	}

	/**
	 * Checks if {@link ThreadContext} exists for the current thread
	 * 
	 * @return {@code true} if {@link ThreadContext} exists for the current thread
	 */
	public static boolean exists()
	{
		return get(false) != null;
	}

	/**
	 * @return {@link Application} bound to current thread
	 */
	public static Application getApplication()
	{
		ThreadContext context = get(false);
		return context != null ? context.application : null;
	}

	/**
	 * Binds the specified application to current thread.
	 * 
	 * @param application
	 */
	public static void setApplication(Application application)
	{
		ThreadContext context = get(true);
		context.application = application;
	}

	/**
	 * @return {@link RequestCycle} bound to current thrad
	 */
	public static RequestCycle getRequestCycle()
	{
		ThreadContext context = get(false);
		return context != null ? context.requestCycle : null;
	}

	/**
	 * Binds the {@link RequestCycle} to current thread.
	 * 
	 * @param requestCycle
	 */
	public static void setRequestCycle(RequestCycle requestCycle)
	{
		ThreadContext context = get(true);
		context.requestCycle = requestCycle;
	}

	/**
	 * @return {@link Session} bound to current thread
	 */
	public static Session getSession()
	{
		ThreadContext context = get(false);
		return context != null ? context.session : null;
	}

	/**
	 * Binds the session to current thread.
	 * 
	 * @param session
	 */
	public static void setSession(Session session)
	{
		ThreadContext context = get(true);
		context.session = session;
	}

	/**
	 * Cleans the {@link ThreadContext} and returns previous context.
	 * 
	 * @return old {@link ThreadContext}
	 */
	public static ThreadContext detach()
	{
		ThreadContext value = threadLocal.get();
		threadLocal.remove();
		return value;
	}

	/**
	 * Restores the context
	 * 
	 * @param threadContext
	 * @see #detach()
	 */
	public static void restore(ThreadContext threadContext)
	{
		if (threadContext == null)
		{
			threadLocal.remove();
		}
		else
		{
			threadLocal.set(threadContext);
		}
	}

	/**
	 * Construct.
	 */
	private ThreadContext()
	{
	}
}