/**
* 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.activemq.broker.region.policy;
import org.apache.activemq.broker.region.MessageReference;
import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
/**
* An eviction strategy which evicts the oldest message within messages with the same property value
*
*
* @org.apache.xbean.XBean
*
*/
public class UniquePropertyMessageEvictionStrategy extends MessageEvictionStrategySupport {
protected String propertyName;
public String getPropertyName() {
return propertyName;
}
public void setPropertyName(String propertyName) {
this.propertyName = propertyName;
}
@Override
public MessageReference[] evictMessages(LinkedList messages) throws IOException {
MessageReference oldest = (MessageReference)messages.getFirst();
HashMap<Object, MessageReference> pivots = new HashMap<Object, MessageReference>();
Iterator iter = messages.iterator();
for (int i = 0; iter.hasNext(); i++) {
MessageReference reference = (MessageReference) iter.next();
if (propertyName != null && reference.getMessage().getProperty(propertyName) != null) {
Object key = reference.getMessage().getProperty(propertyName);
if (pivots.containsKey(key)) {
MessageReference pivot = pivots.get(key);
if (reference.getMessage().getTimestamp() > pivot.getMessage().getTimestamp()) {
pivots.put(key, reference);
}
} else {
pivots.put(key, reference);
}
}
}
if (!pivots.isEmpty()) {
for (MessageReference ref : pivots.values()) {
messages.remove(ref);
}
if (messages.size() != 0) {
return (MessageReference[])messages.toArray(new MessageReference[messages.size()]);
}
}
return new MessageReference[] {oldest};
}
}