ActiveMQ example source code file (PriorityNetworkDispatchPolicy.java)

This example ActiveMQ source code file (PriorityNetworkDispatchPolicy.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - ActiveMQ tags/keywords

arraylist, consumerid, consumerid, consumerinfo, consumerinfo, iterator, list, list, logger, messageevaluationcontext, override, simpledispatchpolicy, subscription, subscription, util

The ActiveMQ PriorityNetworkDispatchPolicy.java source code

/**
 * 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 java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.activemq.broker.region.MessageReference;
import org.apache.activemq.broker.region.Subscription;
import org.apache.activemq.command.ConsumerId;
import org.apache.activemq.command.ConsumerInfo;
import org.apache.activemq.filter.MessageEvaluationContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * dispatch policy that ignores lower priority duplicate network consumers,
 * used in conjunction with network bridge suppresDuplicateTopicSubscriptions
 * 
 * @org.apache.xbean.XBean
 */
public class PriorityNetworkDispatchPolicy extends SimpleDispatchPolicy {

    private static final Logger LOG = LoggerFactory.getLogger(PriorityNetworkDispatchPolicy.class);
    @Override
    public boolean dispatch(MessageReference node,
            MessageEvaluationContext msgContext,
            List<Subscription> consumers) throws Exception {
        
        List<Subscription> duplicateFreeSubs = new ArrayList();
        synchronized (consumers) {
            for (Subscription sub: consumers) {
                ConsumerInfo info = sub.getConsumerInfo();
                if (info.isNetworkSubscription()) {    
                    boolean highestPrioritySub = true;
                    for (Iterator<Subscription> it =  duplicateFreeSubs.iterator(); it.hasNext(); ) {
                        Subscription candidate = it.next();
                        if (matches(candidate, info)) {
                            if (hasLowerPriority(candidate, info)) {
                                it.remove();
                            } else {
                                // higher priority matching sub exists
                                highestPrioritySub = false;
                                if (LOG.isDebugEnabled()) {
                                LOG.debug("ignoring lower priority: " + candidate 
                                        + "[" +candidate.getConsumerInfo().getNetworkConsumerIds() +", "
                                        + candidate.getConsumerInfo().getNetworkConsumerIds() +"] in favour of: " 
                                        + sub
                                        + "[" +sub.getConsumerInfo().getNetworkConsumerIds() +", "
                                        + sub.getConsumerInfo().getNetworkConsumerIds() +"]");
                                }
                            }
                        }
                    }
                    if (highestPrioritySub) {
                        duplicateFreeSubs.add(sub);
                    } 
                } else {
                    duplicateFreeSubs.add(sub);
                }
            }
        }
        
        return super.dispatch(node, msgContext, duplicateFreeSubs);
    }

    private boolean hasLowerPriority(Subscription candidate,
            ConsumerInfo info) {
       return candidate.getConsumerInfo().getPriority() < info.getPriority();
    }

    private boolean matches(Subscription candidate, ConsumerInfo info) {
        boolean matched = false;
        for (ConsumerId candidateId: candidate.getConsumerInfo().getNetworkConsumerIds()) {
            for (ConsumerId subId: info.getNetworkConsumerIds()) {
                if (candidateId.equals(subId)) {
                    matched = true;
                    break;
                }
            }
        }
        return matched;
    }

}