001// Copyright 2014 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.tapestry5.internal.services;
016
017import org.apache.tapestry5.TapestryConstants;
018import org.apache.tapestry5.ioc.IOOperation;
019import org.apache.tapestry5.ioc.OperationTracker;
020import org.apache.tapestry5.services.*;
021
022import java.io.IOException;
023
024/**
025 * After processing the component event request (including Ajax requests), or the page render request,
026 * checks for the {@link org.apache.tapestry5.TapestryConstants#RESPONSE_RENDERER} request attribute,
027 * and invokes it to render the deferred response.
028 *
029 * @since 5.4
030 */
031public class DeferredResponseRenderer implements ComponentRequestFilter
032{
033    private final Request request;
034
035    private final OperationTracker tracker;
036
037    public DeferredResponseRenderer(Request request, OperationTracker tracker)
038    {
039        this.request = request;
040        this.tracker = tracker;
041    }
042
043    public void handleComponentEvent(ComponentEventRequestParameters parameters, ComponentRequestHandler handler) throws IOException
044    {
045        handler.handleComponentEvent(parameters);
046
047        invokeQueuedRenderer();
048    }
049
050    public void handlePageRender(PageRenderRequestParameters parameters, ComponentRequestHandler handler) throws IOException
051    {
052        handler.handlePageRender(parameters);
053
054        invokeQueuedRenderer();
055    }
056
057    private void invokeQueuedRenderer() throws IOException
058    {
059        while (true)
060        {
061
062            IOOperation responseRenderer = (IOOperation) request.getAttribute(TapestryConstants.RESPONSE_RENDERER);
063
064            if (responseRenderer == null)
065            {
066                break;
067            }
068
069            // There's a particular case where an operation puts a different operation into the attribute;
070            // we'll handle that on the next pass.
071            request.setAttribute(TapestryConstants.RESPONSE_RENDERER, null);
072
073            tracker.perform("Executing deferred response renderer.", responseRenderer);
074        }
075    }
076}