tapestry/tapestry-portlet/src/java/org/apache/tapestry/portlet/RenderService.java

// Copyright 2005 The Apache Software Foundation
//
// 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 org.apache.tapestry.portlet;

import java.io.IOException;

import javax.portlet.PortletRequest;

import org.apache.tapestry.IRequestCycle;
import org.apache.tapestry.engine.IEngineService;
import org.apache.tapestry.engine.ILink;
import org.apache.tapestry.services.ServiceConstants;

/**
 * Responsible for rendering out a page; a Portlet render URL is built during
 * action processing that stores the active page; this is the page that will be
 * rendered. The render service is (typically) the only service that operates
 * during a portlet RenderRequest. All other services will be an ActionRequest
 * that (via {@link org.apache.tapestry.portlet.PortletResponseRenderer},
 * writes query parameters to activate this service during the render request.
 * <p>
 * Problematic is is anything related to the portlet mode or window state. As
 * per the Portlet spec, when the user clicks the "help" or "edit" buttons (or
 * the minimize, maximize, etc.), this causes a new RenderRequest, but
 * explicitly keeps the render parameters set by the most recent ActionRequest.
 * But what Tapestry needs is to detect that the mode or state has changed and
 * select a different page to render the response. So we store the mode and
 * state in effect when the ActionRequest executed as two more query parameters,
 * and detect changes to mode and state that way. If there is a change, then we
 * ignore the page query parameter and use the {@link PortletPageResolver} to
 * figure out the correct page to display instead.
 * 
 * @author Howard M. Lewis Ship
 * @since 4.0
 * @see org.apache.tapestry.services.impl.ResponseRendererImpl
 */
public class RenderService implements IEngineService
{

    private PortletRequest _request;

    private PortletRenderer _portletRenderer;

    private PortletPageResolver _pageResolver;

    public ILink getLink(boolean post, Object parameter)
    {
        throw new UnsupportedOperationException(PortletMessages
                .unsupportedMethod("getLink"));
    }

    public void service(IRequestCycle cycle)
        throws IOException
    {
        String pageName = getPageNameToRender(cycle);

        _portletRenderer.renderPage(cycle, pageName);
    }

    private String getPageNameToRender(IRequestCycle cycle)
    {
        if (isStateChange(cycle))
            return _pageResolver.getPageNameForRequest(cycle);

        return cycle.getParameter(ServiceConstants.PAGE);
    }

    /**
     * Returns true if the portlet mode or the window state has changed since.
     * The values stored previously (during an action request) are compared to
     * the current values.
     */

    boolean isStateChange(IRequestCycle cycle)
    {
        String expectedPortletMode = cycle
                .getParameter(PortletConstants.PORTLET_MODE);
        String expectedWindowState = cycle
                .getParameter(PortletConstants.WINDOW_STATE);

        return !(_request.getPortletMode().toString().equals(
                expectedPortletMode) && _request.getWindowState().toString()
                .equals(expectedWindowState));

    }

    public String getName()
    {
        return PortletConstants.RENDER_SERVICE;
    }

    public void setPortletRenderer(PortletRenderer portletRenderer)
    {
        _portletRenderer = portletRenderer;
    }

    public void setRequest(PortletRequest request)
    {
        _request = request;
    }

    public void setPageResolver(PortletPageResolver pageResolver)
    {
        _pageResolver = pageResolver;
    }
}