001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.activemq.broker.region.policy; 018 019 import java.util.Iterator; 020 import java.util.List; 021 import org.apache.activemq.broker.region.MessageReference; 022 import org.apache.activemq.broker.region.Subscription; 023 import org.apache.activemq.filter.MessageEvaluationContext; 024 025 /** 026 * Dispatch policy that causes every subscription to see messages in the same 027 * order. 028 * 029 * @org.apache.xbean.XBean 030 * @version $Revision$ 031 */ 032 public class StrictOrderDispatchPolicy implements DispatchPolicy { 033 034 /** 035 * @param node 036 * @param msgContext 037 * @param consumers 038 * @return true if dispatched 039 * @throws Exception 040 * @see org.apache.activemq.broker.region.policy.DispatchPolicy#dispatch(org.apache.activemq.broker.region.MessageReference, 041 * org.apache.activemq.filter.MessageEvaluationContext, java.util.List) 042 */ 043 public boolean dispatch(MessageReference node, MessageEvaluationContext msgContext, List consumers) throws Exception { 044 // Big synch here so that only 1 message gets dispatched at a time. 045 // Ensures 046 // Everyone sees the same order. 047 synchronized (consumers) { 048 int count = 0; 049 for (Iterator iter = consumers.iterator(); iter.hasNext();) { 050 Subscription sub = (Subscription)iter.next(); 051 052 // Only dispatch to interested subscriptions 053 if (!sub.matches(node, msgContext)) { 054 continue; 055 } 056 057 sub.add(node); 058 count++; 059 } 060 return count > 0; 061 } 062 } 063 064 }