actioneventcontextholder.java

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/*
 * Copyright 2002-2004 the original author or authors.
 *
 * 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 de.mindmatters.faces.application;

import javax.faces.event.ActionEvent;

/**
 * Simple holder class that associates a <strong>{@link ActionEventContext}</strong>
 * instance with the current thread. The ActionEventContext will be inherited by
 * any child threads spawned by the current thread.
 * 
 * <p>
 * Used as a central holder for the current ActionEvent in JSF-Spring, wherever
 * necessary: for example, in concrete controller instances. <strong>{@link DelegatingActionListener}</strong>
 * automatically exposes its current ActionEvent here.
 * </p>
 * 
 * @author Andreas Kuhrwahl
 * @see DelegatingActionListener#processAction(ActionEvent)
 * 
 */
public final class ActionEventContextHolder {

    /** Holds the context. */
    private static final ThreadLocal ACTION_EVENT_CONTEXT_HOLDER = new InheritableThreadLocal();

    /**
     * It's a static class.
     */
    private ActionEventContextHolder() {
        super();
    }

    /**
     * Associate the given ActionEventContext with the current thread.
     * 
     * @param actionEventContext
     *            the current ActionEventContext, or <code>null</code> to
     *            reset the thread-bound context
     */
    public static void setActionEventContext(
            final ActionEventContext actionEventContext) {
        ACTION_EVENT_CONTEXT_HOLDER.set(actionEventContext);
    }

    /**
     * Return the ActionEventContext associated with the current thread, if any.
     * 
     * @return the current ActionEventContext, or <code>null</code> if none
     */
    public static ActionEventContext getActionEventContext() {
        return (ActionEventContext) ACTION_EVENT_CONTEXT_HOLDER.get();
    }

    /**
     * Associate the given ActionEvent with the current thread. Will implicitly
     * create a ActionEventContext for the given ActionEvent.
     * 
     * @param actionEvent
     *            the current ActionEvent, or <code>null</code> to reset the
     *            thread-bound context
     * @see SimpleActionEventContext#SimpleActionEventContext(ActionEvent)
     */
    public static void setActionEvent(final ActionEvent actionEvent) {
        ActionEventContext actionEventContext = null;
        if (actionEvent != null) {
            actionEventContext = new SimpleActionEventContext(actionEvent);
        }
        ACTION_EVENT_CONTEXT_HOLDER.set(actionEventContext);
    }

    /**
     * Return the ActionEvent associated with the current thread, if any.
     * 
     * @return the current ActionEvent, or <code>null</code> if no specific
     *         ActionEvent has been associated with the current thread
     * @see ActionEventContext#getActionEvent()
     */
    public static ActionEvent getActionEvent() {
        ActionEvent actionEvent = null;
        ActionEventContext actionEventContext = (ActionEventContext) ACTION_EVENT_CONTEXT_HOLDER
                .get();
        if (actionEventContext != null) {
            actionEvent = actionEventContext.getActionEvent();
        }
        return actionEvent;
    }

}