    001//  Copyright 2008, 2009, 2012 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.ComponentEventCallback;
    018import org.apache.tapestry5.EventConstants;
    019import org.apache.tapestry5.commons.services.InvalidationEventHub;
    020import org.apache.tapestry5.commons.services.InvalidationListener;
    021import org.apache.tapestry5.commons.services.TypeCoercer;
    022import org.apache.tapestry5.commons.util.CollectionFactory;
    023import org.apache.tapestry5.internal.structure.ComponentPageElement;
    024import org.apache.tapestry5.internal.structure.Page;
    025import org.apache.tapestry5.internal.util.Holder;
    026import org.apache.tapestry5.ioc.annotations.ComponentClasses;
    027import org.apache.tapestry5.ioc.annotations.PostInjection;
    028import org.apache.tapestry5.model.ComponentModel;
    029
    030import java.util.Map;
    031
    032public class PageActivationContextCollectorImpl implements PageActivationContextCollector
    033{
    034    private final Object[] EMPTY = new Object[0];
    035
    036    private final TypeCoercer typeCoercer;
    037
    038    private final ComponentModelSource modelSource;
    039
    040    private final RequestPageCache requestPageCache;
    041
    042    /**
    043     * Keyed on *canonical* page name, value indicates whether the page has a passivate event handler.
    044     */
    045    private final Map<String, Boolean> cache = CollectionFactory.newConcurrentMap();
    046
    047    public PageActivationContextCollectorImpl(TypeCoercer typeCoercer, RequestPageCache requestPageCache,
    048                                              ComponentModelSource modelSource)
    049    {
    050        this.typeCoercer = typeCoercer;
    051        this.requestPageCache = requestPageCache;
    052        this.modelSource = modelSource;
    053
    054    }
    055
    056    @PostInjection
    057    public void setupInvalidation(@ComponentClasses InvalidationEventHub invalidationEventHub)
    058    {
    059        invalidationEventHub.clearOnInvalidation(cache);
    060    }
    061
    062    public Object[] collectPageActivationContext(String pageName)
    063    {
    064        Boolean hasHandler = cache.get(pageName);
    065
    066        if (hasHandler == null)
    067        {
    068            ComponentModel model = modelSource.getPageModel(pageName);
    069
    070            hasHandler = model.handlesEvent(EventConstants.PASSIVATE);
    071
    072            cache.put(pageName, hasHandler);
    073        }
    074
    075        // If no handler for the event, then no need to fire the event (and more importantly,
    076        // no need to obtain a page instance!)
    077
    078        if (!hasHandler)
    079            return EMPTY;
    080
    081        // Get or create a page instance and trigger the event.
    082
    083        Page page = requestPageCache.get(pageName);
    084
    085        ComponentPageElement element = page.getRootElement();
    086
    087        final Holder<Object[]> holder = Holder.create();
    088
    089        ComponentEventCallback callback = new ComponentEventCallback()
    090        {
    091            public boolean handleResult(Object result)
    092            {
    093                holder.put(typeCoercer.coerce(result, Object[].class));
    094
    095                // We've got the value, stop the event.
    096
    097                return true;
    098            }
    099        };
    100
    101        element.triggerEvent(EventConstants.PASSIVATE, null, callback);
    102
    103        if (!holder.hasValue()) return EMPTY;
    104
    105        return holder.get();
    106    }
    107}