/*
* 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.util.regex.Pattern;
import org.apache.wicket.request.resource.caching.IStaticCacheableResource;
import org.apache.wicket.util.resource.IResourceStream;
import org.apache.wicket.util.time.Time;
/**
* Uses the last modified timestamp of a {@link org.apache.wicket.request.resource.caching.IStaticCacheableResource}
* converted to milliseconds as a version string.
*
* @author Peter Ertl
*
* @since 1.5
*/
public class LastModifiedResourceVersion implements IResourceVersion
{
/**
* A valid pattern is a sequence of digits
*/
private static final Pattern TIMESTAMP_PATTERN = Pattern.compile("[0-9]+");
@Override
public String getVersion(IStaticCacheableResource resource)
{
// get last modified timestamp of resource
IResourceStream stream = resource.getCacheableResourceStream();
// if resource stream can not be found do not cache
if (stream == null)
{
return null;
}
final Time lastModified = stream.lastModifiedTime();
// if no timestamp is available we can not provide a version
if (lastModified == null)
{
return null;
}
// version string = last modified timestamp converted to milliseconds
return String.valueOf(lastModified.getMilliseconds()).intern();
}
@Override
public Pattern getVersionPattern()
{
return TIMESTAMP_PATTERN;
}
}