001// Copyright 2005 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry.portlet;
016
017import java.io.IOException;
018
019import javax.portlet.PortletRequest;
020
021import org.apache.tapestry.IRequestCycle;
022import org.apache.tapestry.engine.IEngineService;
023import org.apache.tapestry.engine.ILink;
024import org.apache.tapestry.services.ServiceConstants;
025
026/**
027 * Responsible for rendering out a page; a Portlet render URL is built during action processing that
028 * stores the active page; this is the page that will be rendered. The render service is (typically)
029 * the only service that operates during a portlet RenderRequest. All other services will be an
030 * ActionRequest that (via {@link org.apache.tapestry.portlet.PortletResponseRenderer}, writes
031 * query parameters to activate this service during the render request.
032 * <p>
033 * Problematic is is anything related to the portlet mode or window state. As per the Portlet spec,
034 * when the user clicks the "help" or "edit" buttons (or the minimize, maximize, etc.), this causes
035 * a new RenderRequest, but explicitly keeps the render parameters set by the most recent
036 * ActionRequest. But what Tapestry needs is to detect that the mode or state has changed and select
037 * a different page to render the response. So we store the mode and state in effect when the
038 * ActionRequest executed as two more query parameters, and detect changes to mode and state that
039 * way. If there is a change, then we ignore the page query parameter and use the
040 * {@link PortletPageResolver} to figure out the correct page to display instead.
041 * 
042 * @author Howard M. Lewis Ship
043 * @since 4.0
044 * @see org.apache.tapestry.services.impl.ResponseRendererImpl
045 */
046public class RenderService implements IEngineService
047{
048    private PortletRequest _request;
049
050    private PortletRenderer _portletRenderer;
051
052    private PortletPageResolver _pageResolver;
053
054    public ILink getLink(boolean post, Object parameter)
055    {
056        throw new UnsupportedOperationException(PortletMessages.unsupportedMethod("getLink"));
057    }
058
059    public void service(IRequestCycle cycle) throws IOException
060    {
061        String pageName = getPageNameToRender(cycle);
062
063        _portletRenderer.renderPage(cycle, pageName);
064    }
065
066    private String getPageNameToRender(IRequestCycle cycle)
067    {
068        if (isStateChange(cycle))
069            return _pageResolver.getPageNameForRequest(cycle);
070
071        return cycle.getParameter(ServiceConstants.PAGE);
072    }
073
074    /**
075     * Returns true if the portlet mode or the window state has changed since. The values stored
076     * previously (during an action request) are compared to the current values.
077     */
078
079    boolean isStateChange(IRequestCycle cycle)
080    {
081        String expectedPortletMode = cycle.getParameter(PortletConstants.PORTLET_MODE);
082        String expectedWindowState = cycle.getParameter(PortletConstants.WINDOW_STATE);
083
084        return !(_request.getPortletMode().toString().equals(expectedPortletMode) && _request
085                .getWindowState().toString().equals(expectedWindowState));
086
087    }
088
089    public String getName()
090    {
091        return PortletConstants.RENDER_SERVICE;
092    }
093
094    public void setPortletRenderer(PortletRenderer portletRenderer)
095    {
096        _portletRenderer = portletRenderer;
097    }
098
099    public void setRequest(PortletRequest request)
100    {
101        _request = request;
102    }
103
104    public void setPageResolver(PortletPageResolver pageResolver)
105    {
106        _pageResolver = pageResolver;
107    }
108}