// Copyright 2006 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.apache.tapestry.internal.services;
import static org.apache.tapestry.ioc.internal.util.CollectionFactory.newThreadSafeMap;
import java.net.URL;
import java.util.Map;
import org.apache.tapestry.events.UpdateListener;
import org.apache.tapestry.internal.event.InvalidationEventHubImpl;
import org.apache.tapestry.internal.util.URLChangeTracker;
import org.apache.tapestry.ioc.Resource;
import org.apache.tapestry.services.ResourceDigestGenerator;
public class ResourceCacheImpl extends InvalidationEventHubImpl implements ResourceCache,
UpdateListener
{
private final URLChangeTracker _tracker;
private final ResourceDigestGenerator _digestGenerator;
private final Map<Resource, Cached> _cache = newThreadSafeMap();
final static long MISSING_RESOURCE_TIME_MODIFIED = -1l;
private class Cached
{
final boolean _requiresDigest;
final String _digest;
final long _timeModified;
Cached(Resource resource)
{
_requiresDigest = _digestGenerator.requiresDigest(resource.getPath());
URL url = resource.toURL();
// The url may be null when a request for a protected asset arrives, because the
// Resource initially is for the file with the digest incorporated into the path, which
// means
// no underlying file exists. Subsequently, we'll strip out the digest and resolve
// to an actual resource.
_digest = (_requiresDigest && url != null) ? _digestGenerator.generateDigest(url)
: null;
_timeModified = url != null ? _tracker.add(url) : MISSING_RESOURCE_TIME_MODIFIED;
}
}
public ResourceCacheImpl(final ResourceDigestGenerator digestGenerator)
{
this(digestGenerator, new URLChangeTracker());
}
ResourceCacheImpl(final ResourceDigestGenerator digestGenerator, URLChangeTracker tracker)
{
_digestGenerator = digestGenerator;
_tracker = tracker;
}
public void checkForUpdates()
{
if (_tracker.containsChanges())
{
_cache.clear();
_tracker.clear();
fireInvalidationEvent();
}
}
private Cached get(Resource resource)
{
Cached result = _cache.get(resource);
if (result == null)
{
result = new Cached(resource);
_cache.put(resource, result);
}
return result;
}
public String getDigest(Resource resource)
{
return get(resource)._digest;
}
public long getTimeModified(Resource resource)
{
return get(resource)._timeModified;
}
public boolean requiresDigest(Resource resource)
{
return get(resource)._requiresDigest;
}
}