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Jakarta Faces defines an MVC framework for building user interfaces for web applications, including UI components, state management, event handing, input validation, page navigation, and support for internationalization and accessibility.

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/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.faces.context;

import javax.faces.FacesWrapper;

/**
 * FlashFactory is a
 * factory object that creates (if needed) and returns {@link Flash}
 * instances.  Implementations of JavaServer Faces must provide at
 * least a default implementation of {@link Flash}.

 * 
 *
 * There must be one {@link FlashFactory} instance per web
 * application that is utilizing JavaServer Faces.  This instance can
 * be acquired, in a portable manner, by calling:
 *  *   FlashFactory factory = (FlashFactory)
 *     FactoryFinder.getFactory(FactoryFinder.FLASH_FACTORY);
 * 

 * The common way to access the flash instance from Java code is
 * still via {@link ExternalContext#getFlash}.  The common way to access
 * the flash from Faces views is the implicit EL object "flash".  The
 * runtime must ensure that the FlashFactory is used to
 * instantiate the flash.

 * 
 *
 * Usage: extend this class and push the implementation being wrapped to the
 * constructor and use {@link #getWrapped} to access the instance being wrapped.
 *
 * @since 2.2
 */
public abstract class FlashFactory implements FacesWrapper {

    private FlashFactory wrapped;

    /**
     * @deprecated Use the other constructor taking the implementation being wrapped.
     */
    @Deprecated
    public FlashFactory() {

    }

    /**
     * If this factory has been decorated,
     * the implementation doing the decorating should push the implementation being wrapped to this constructor.
     * The {@link #getWrapped()} will then return the implementation being wrapped.
     *
     * @param wrapped The implementation being wrapped.
     */
    public FlashFactory(FlashFactory wrapped) {
        this.wrapped = wrapped;
    }

    /**
     * If this factory has been decorated, the
     * implementation doing the decorating may override this method to provide
     * access to the implementation being wrapped.
     */
    @Override
    public FlashFactory getWrapped() {
        return wrapped;
    }

    /**
     * Create (if needed) and return a
     * {@link Flash} instance for this web application.
     *
     * @param create true to create a new instance for this request if
     * necessary; false to return null if there's no
     * instance in the current session.
     *
     *  @return the instance of Flash.
     *
     * @since 2.2
     */
    public abstract Flash getFlash(boolean create);

}