/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.wicket.request.resource.caching.version;
import java.io.Serializable;
import java.util.Map;
import java.util.regex.Pattern;
import org.apache.wicket.MetaDataKey;
import org.apache.wicket.ThreadContext;
import org.apache.wicket.request.cycle.RequestCycle;
import org.apache.wicket.request.resource.caching.IStaticCacheableResource;
import org.apache.wicket.util.lang.Args;
import org.apache.wicket.util.lang.Generics;
/**
* Caches the results of a delegating {@link IResourceVersion} instance
* for the lifetime of the current http request.
*
* @author Peter Ertl
*
* @since 1.5
*/
public class RequestCycleCachedResourceVersion implements IResourceVersion
{
private static final MetaDataKey<Map<Serializable, String>> CACHE_KEY =
new MetaDataKey<Map<Serializable, String>>()
{
private static final long serialVersionUID = 1L;
};
/**
* resource version provider which will actually do
* the hard work and retrieve the version
*/
private final IResourceVersion delegate;
/**
* create request-scoped resource provider cache
*
* @param delegate
* resource version provider to cache
*/
public RequestCycleCachedResourceVersion(IResourceVersion delegate)
{
this.delegate = Args.notNull(delegate, "delegate");
}
@Override
public String getVersion(IStaticCacheableResource resource)
{
// get current request cycle
final RequestCycle requestCycle = ThreadContext.getRequestCycle();
// cache instance
Map<Serializable, String> cache = null;
// cache key
Serializable key = null;
// is request cycle available?
if (requestCycle != null)
{
// retrieve cache from current request cycle
cache = requestCycle.getMetaData(CACHE_KEY);
// create caching key
key = resource.getCacheKey();
// does cache exist within current request cycle?
if (cache == null)
{
// no, so create it
requestCycle.setMetaData(CACHE_KEY, cache = Generics.newHashMap());
}
else if (cache.containsKey(key))
{
// lookup timestamp from cache (may contain NULL values which are valid)
return cache.get(key);
}
}
// no cache entry found, query version from delegate
final String version = delegate.getVersion(resource);
// store value in cache (if it is available)
if (cache != null && key != null)
{
cache.put(key, version);
}
return version;
}
@Override
public Pattern getVersionPattern()
{
return delegate.getVersionPattern();
}
}