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
015package org.apache.tapestry5.internal.services;
016
017import org.apache.tapestry5.ComponentEventCallback;
018import org.apache.tapestry5.EventConstants;
019import org.apache.tapestry5.internal.structure.ComponentPageElement;
020import org.apache.tapestry5.internal.structure.Page;
021import org.apache.tapestry5.internal.util.Holder;
022import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
023import org.apache.tapestry5.ioc.services.TypeCoercer;
024import org.apache.tapestry5.model.ComponentModel;
025import org.apache.tapestry5.services.InvalidationListener;
026
027import java.util.Map;
028
029public 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}