001// Copyright 2011 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.dynamic;
016
017import org.apache.tapestry5.internal.services.PageSource;
018import org.apache.tapestry5.internal.services.TemplateParser;
019import org.apache.tapestry5.ioc.Resource;
020import org.apache.tapestry5.ioc.annotations.PostInjection;
021import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
022import org.apache.tapestry5.ioc.internal.util.URLChangeTracker;
023import org.apache.tapestry5.ioc.services.ClasspathURLConverter;
024import org.apache.tapestry5.services.BindingSource;
025import org.apache.tapestry5.services.UpdateListener;
026import org.apache.tapestry5.services.UpdateListenerHub;
027import org.apache.tapestry5.services.dynamic.DynamicTemplate;
028import org.apache.tapestry5.services.dynamic.DynamicTemplateParser;
029
030import java.util.Map;
031
032public class DynamicTemplateParserImpl implements DynamicTemplateParser, UpdateListener
033{
034    private final Map<Resource, DynamicTemplate> cache = CollectionFactory.newConcurrentMap();
035
036    private final BindingSource bindingSource;
037
038    private final PageSource pageSource;
039
040    private final URLChangeTracker tracker;
041
042    private final TemplateParser componentTemplateParser;
043
044    public DynamicTemplateParserImpl(ClasspathURLConverter converter, BindingSource bindingSource, PageSource pageSource, TemplateParser componentTemplateParser)
045    {
046        this.bindingSource = bindingSource;
047        this.pageSource = pageSource;
048        this.componentTemplateParser = componentTemplateParser;
049
050        tracker = new URLChangeTracker(converter);
051    }
052
053    @PostInjection
054    public void registerAsUpdateListener(UpdateListenerHub hub)
055    {
056        hub.addUpdateListener(this);
057    }
058
059    public DynamicTemplate parseTemplate(Resource resource)
060    {
061        DynamicTemplate result = cache.get(resource);
062
063        if (result == null)
064        {
065            result = doParse(resource);
066            cache.put(resource, result);
067
068            tracker.add(resource.toURL());
069        }
070
071        return result;
072    }
073
074    private DynamicTemplate doParse(Resource resource)
075    {
076        return new DynamicTemplateSaxParser(resource, bindingSource, componentTemplateParser.getDTDURLMappings()).parse();
077    }
078
079    public void checkForUpdates()
080    {
081        if (tracker.containsChanges())
082        {
083            tracker.clear();
084            cache.clear();
085
086            // A typical case is that a "context:" or "asset:" binding is used with the Dynamic component's template
087            // parameter. This causes the Asset to be converted to a Resource and parsed. However, those are invariant
088            // bindings, so even if it is discovered that the underlying file has changed, the parsed template
089            // is still cached inside the component. Clearing the page pool forces the page instance to be
090            // rebuilt, which is a crude way of clearing out that data. Other alternatives exist, such as
091            // yielding up a proxy to the DynamicTemplate that is more change-aware.
092
093            pageSource.clearCache();
094        }
095    }
096
097}