/*
* Copyright 2006-2007 the original author or authors.
*
* 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.springframework.batch.support;
import java.io.IOException;
import java.util.Comparator;
import org.springframework.core.io.Resource;
import org.springframework.util.Assert;
/**
* Comparator to sort resources by the file last modified time.
*
* @author Dave Syer
*
*/
public class LastModifiedResourceComparator implements Comparator<Resource> {
/**
* Compare the two resources by last modified time, so that a sorted list of
* resources will have oldest first.
*
* @throws IllegalArgumentException if one of the resources doesn't exist or
* its last modified date cannot be determined
*
* @see Comparator#compare(Object, Object)
*/
@Override
public int compare(Resource r1, Resource r2) {
Assert.isTrue(r1.exists(), "Resource does not exist: " + r1);
Assert.isTrue(r2.exists(), "Resource does not exist: " + r2);
try {
long diff = r1.getFile().lastModified() - r2.getFile().lastModified();
return diff > 0 ? 1 : diff < 0 ? -1 : 0;
}
catch (IOException e) {
throw new IllegalArgumentException("Resource modification times cannot be determined (unexpected).", e);
}
}
}