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/*****************************************************************************
 * Copyright (C) NanoContainer Organization. All rights reserved.            *
 * ------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the BSD      *
 * style license a copy of which has been included with this distribution in *
 * the LICENSE.txt file.                                                     *
 *                                                                           *
 *****************************************************************************/
package org.nanocontainer.nanowar.struts;

import javax.servlet.http.HttpServletRequest;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionServlet;
import org.nanocontainer.nanowar.ActionsContainerFactory;
import org.picocontainer.MutablePicoContainer;
import org.picocontainer.PicoInitializationException;
import org.picocontainer.PicoIntrospectionException;

/**
 * Uses PicoContainer to produce Actions and inject dependencies into them. 
 * If you have your own RequestProcessor implementation, you can use an
 * ActionFactory in your RequestProcessor.processActionCreate 
 * method to Picofy your Actions.
 * 
 * @author Stephen Molitor
 * @author Mauro Talevi
 */
public class ActionFactory {
    
     private ActionsContainerFactory actionsContainerFactory = new ActionsContainerFactory();

    /**
     * Gets the Action specified by the mapping type from a PicoContainer. 
     * The action will be instantiated if necessary, and its
     * dependencies will be injected. The action will be instantiated via a
     * special PicoContainer that just contains actions. If this container
     * already exists in the request attribute, this method will use it. If no
     * such container exists, this method will create a new Pico container and
     * place it in the request. The parent container will either be the request
     * container, or if that container can not be found the session container,
     * or if that container can not be found, the application container. If no
     * parent container can be found, a PicoInitializationException
     * will be thrown. The action path specified in the mapping is used as
     * the component key for the action.
     * 
     * @param request the Http servlet request.
     * @param mapping the Struts mapping object, whose type property tells us what
     *        Action class is required.
     * @param servlet the Struts ActionServlet.  
     * @return the Action instance.
     * @throws PicoIntrospectionException  if the mapping type does not specify a valid action.
     * @throws PicoInitializationException if no request, session, or application scoped Pico container
     *                                     can be found.
     */
    public Action getAction(HttpServletRequest request, ActionMapping mapping, ActionServlet servlet)
            throws PicoIntrospectionException, PicoInitializationException {

        MutablePicoContainer actionsContainer = actionsContainerFactory.getActionsContainer(request);
        Object actionKey = mapping.getPath();
        Class actionType = actionsContainerFactory.getActionClass(mapping.getType());

        Action action = (Action) actionsContainer.getComponentInstance(actionKey);
        if (action == null) {
            actionsContainer.registerComponentImplementation(actionKey, actionType);
            action = (Action) actionsContainer.getComponentInstance(actionKey);
        }

        action.setServlet(servlet);
        return action;
    }

}