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JSF components and utilities that can be used with any JSF implementation. This library is based on the JSF1.1 version of Tomahawk, but with minor source code and build changes to take advantage of JSF2.1 features. A JSF2.1 implementation is required to use this version of the Tomahawk library.
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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.myfaces.shared_tomahawk.view;

import javax.faces.application.Application;
import javax.faces.application.ViewHandler;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;
import javax.faces.view.ViewDeclarationLanguage;

import org.apache.myfaces.shared_tomahawk.application.InvalidViewIdException;

/**
 * @author Simon Lessard (latest modification by $Author: bommel $)
 * @version $Revision: 1187700 $ $Date: 2011-10-22 07:19:37 -0500 (Sat, 22 Oct 2011) $
 * 
 * @since 2.0
 */
public abstract class ViewDeclarationLanguageBase extends ViewDeclarationLanguage
{
    
    /**
     * Process the specification required algorithm that is generic to all PDL.
     * 
     * @param context
     * @param viewId
     */
    public UIViewRoot createView(FacesContext context, String viewId)
    {
        checkNull(context, "context");
        //checkNull(viewId, "viewId");

        try
        {
            viewId = calculateViewId(context, viewId);
            
            Application application = context.getApplication();

            // Create a new UIViewRoot object instance using Application.createComponent(UIViewRoot.COMPONENT_TYPE).
            UIViewRoot newViewRoot = (UIViewRoot) application.createComponent(UIViewRoot.COMPONENT_TYPE);
            UIViewRoot oldViewRoot = context.getViewRoot();
            if (oldViewRoot == null)
            {
                // If not, this method must call calculateLocale() and calculateRenderKitId(), and store the results
                // as the values of the locale and renderKitId, proeprties, respectively, of the newly created
                // UIViewRoot.
                ViewHandler handler = application.getViewHandler();
                newViewRoot.setLocale(handler.calculateLocale(context));
                newViewRoot.setRenderKitId(handler.calculateRenderKitId(context));
            }
            else
            {
                // If there is an existing UIViewRoot available on the FacesContext, this method must copy its locale
                // and renderKitId to this new view root
                newViewRoot.setLocale(oldViewRoot.getLocale());
                newViewRoot.setRenderKitId(oldViewRoot.getRenderKitId());
            }
            
            // TODO: VALIDATE - The spec is silent on the following line, but I feel bad if I don't set it
            newViewRoot.setViewId(viewId);

            return newViewRoot;
        }
        catch (InvalidViewIdException e)
        {
            // If no viewId could be identified, or the viewId is exactly equal to the servlet mapping, 
            // send the response error code SC_NOT_FOUND with a suitable message to the client.
            sendSourceNotFound(context, e.getMessage());
            
            // TODO: VALIDATE - Spec is silent on the return value when an error was sent
            return null;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public UIViewRoot restoreView(FacesContext context, String viewId)
    {
        checkNull(context, "context");
        //checkNull(viewId, "viewId");

        Application application = context.getApplication();
        
        ViewHandler applicationViewHandler = application.getViewHandler();
        
        String renderKitId = applicationViewHandler.calculateRenderKitId(context);

        UIViewRoot viewRoot = application.getStateManager().restoreView(context, viewId, renderKitId);

        return viewRoot;
    }

    /**
     * Calculates the effective view identifier for the specified raw view identifier.
     * 
     * @param context le current FacesContext
     * @param viewId the raw view identifier
     * 
     * @return the effective view identifier
     */
    protected abstract String calculateViewId(FacesContext context, String viewId);
    
    /**
     * Send a source not found to the client. Although it can be considered ok in JSP mode,
     * I think it's pretty lame to have this kind of requirement at VDL level considering VDL 
     * represents the page --> JSF tree link, not the transport layer required to send a 
     * SC_NOT_FOUND.
     * 
     * @param context le current FacesContext
     * @param message the message associated with the error
     */
    protected abstract void sendSourceNotFound(FacesContext context, String message);
    
    /**
     * Check if the specified value of a param is null.
     * 
     * @param o the parameter's value
     * @param param the parameter's name
     * 
     * @throws NullPointerException if the value is null
     */
    protected void checkNull(final Object o, final String param)
    {
        if (o == null)
        {
            throw new NullPointerException(param + " can not be null.");
        }
    }
}