001    //  Copyright 2008, 2009 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    
015    package org.apache.tapestry5.internal.services;
016    
017    import org.apache.tapestry5.ComponentEventCallback;
018    import org.apache.tapestry5.EventConstants;
019    import org.apache.tapestry5.internal.structure.ComponentPageElement;
020    import org.apache.tapestry5.internal.structure.Page;
021    import org.apache.tapestry5.internal.util.Holder;
022    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
023    import org.apache.tapestry5.ioc.services.TypeCoercer;
024    import org.apache.tapestry5.model.ComponentModel;
025    import org.apache.tapestry5.services.InvalidationListener;
026    
027    import java.util.Map;
028    
029    public class PageActivationContextCollectorImpl implements PageActivationContextCollector, InvalidationListener
030    {
031        private final Object[] EMPTY = new Object[0];
032    
033        private final TypeCoercer typeCoercer;
034    
035        private final ComponentModelSource modelSource;
036    
037        private final RequestPageCache requestPageCache;
038    
039        /**
040         * Keyed on *canonical* page name, value indicates whether the page has a passivate event handler.
041         */
042        private final Map<String, Boolean> cache = CollectionFactory.newConcurrentMap();
043    
044        public PageActivationContextCollectorImpl(TypeCoercer typeCoercer, RequestPageCache requestPageCache,
045                                                  ComponentModelSource modelSource)
046        {
047            this.typeCoercer = typeCoercer;
048            this.requestPageCache = requestPageCache;
049            this.modelSource = modelSource;
050        }
051    
052        public void objectWasInvalidated()
053        {
054            cache.clear();
055        }
056    
057        public Object[] collectPageActivationContext(String pageName)
058        {
059            Boolean hasHandler = cache.get(pageName);
060    
061            if (hasHandler == null)
062            {
063                ComponentModel model = modelSource.getPageModel(pageName);
064    
065                hasHandler = model.handlesEvent(EventConstants.PASSIVATE);
066    
067                cache.put(pageName, hasHandler);
068            }
069    
070            // If no handler for the event, then no need to fire the event (and more importantly,
071            // no need to obtain a page instance!)
072    
073            if (!hasHandler)
074                return EMPTY;
075    
076            // Get or create a page instance and trigger the event.
077    
078            Page page = requestPageCache.get(pageName);
079    
080            ComponentPageElement element = page.getRootElement();
081    
082            final Holder<Object[]> holder = Holder.create();
083    
084            ComponentEventCallback callback = new ComponentEventCallback()
085            {
086                public boolean handleResult(Object result)
087                {
088                    holder.put(typeCoercer.coerce(result, Object[].class));
089    
090                    // We've got the value, stop the event.
091    
092                    return true;
093                }
094            };
095    
096            element.triggerEvent(EventConstants.PASSIVATE, null, callback);
097    
098            if (!holder.hasValue()) return EMPTY;
099    
100            return holder.get();
101        }
102    }