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 */
017package org.apache.activemq.broker.region.virtual;
018
019import org.apache.activemq.broker.Broker;
020import org.apache.activemq.broker.ProducerBrokerExchange;
021import org.apache.activemq.broker.region.Destination;
022import org.apache.activemq.broker.region.Subscription;
023import org.apache.activemq.command.ActiveMQDestination;
024import org.apache.activemq.command.Message;
025import org.apache.activemq.filter.BooleanExpression;
026import org.apache.activemq.filter.MessageEvaluationContext;
027import org.apache.activemq.filter.NonCachedMessageEvaluationContext;
028import org.apache.activemq.plugin.SubQueueSelectorCacheBroker;
029import org.apache.activemq.selector.SelectorParser;
030import org.apache.activemq.util.LRUCache;
031import org.slf4j.Logger;
032import org.slf4j.LoggerFactory;
033
034import java.io.IOException;
035import java.util.List;
036import java.util.Set;
037
038public class SelectorAwareVirtualTopicInterceptor extends VirtualTopicInterceptor {
039    private static final Logger LOG = LoggerFactory.getLogger(SelectorAwareVirtualTopicInterceptor.class);
040    LRUCache<String,BooleanExpression> expressionCache = new LRUCache<String,BooleanExpression>();
041    private SubQueueSelectorCacheBroker selectorCachePlugin;
042
043    public SelectorAwareVirtualTopicInterceptor(Destination next, VirtualTopic virtualTopic) {
044        super(next, virtualTopic);
045    }
046
047    /**
048     * Respect the selectors of the subscriptions to ensure only matched messages are dispatched to
049     * the virtual queues, hence there is no build up of unmatched messages on these destinations
050     */
051    @Override
052    protected boolean shouldDispatch(final Broker broker, Message message, Destination dest) throws IOException {
053        boolean matches = false;
054        MessageEvaluationContext msgContext = new NonCachedMessageEvaluationContext();
055        msgContext.setDestination(dest.getActiveMQDestination());
056        msgContext.setMessageReference(message);
057        List<Subscription> subs = dest.getConsumers();
058        for (Subscription sub : subs) {
059            if (sub.matches(message, msgContext)) {
060                matches = true;
061                break;
062            }
063        }
064        if (matches == false) {
065            matches = tryMatchingCachedSubs(broker, dest, msgContext);
066        }
067        return matches;
068    }
069
070    private boolean tryMatchingCachedSubs(final Broker broker, Destination dest, MessageEvaluationContext msgContext) {
071        boolean matches = false;
072        LOG.debug("No active consumer match found. Will try cache if configured...");
073
074        //retrieve the specific plugin class and lookup the selector for the destination.
075        final SubQueueSelectorCacheBroker cache = getSubQueueSelectorCacheBrokerPlugin(broker);
076
077        if (cache != null) {
078            final Set<String> selectors = cache.getSelector(dest.getActiveMQDestination().getQualifiedName());
079            for (String selector : selectors) {
080                try {
081                    final BooleanExpression expression = getExpression(selector);
082                    matches = expression.matches(msgContext);
083                    if (matches) {
084                        return true;
085                    }
086                } catch (Exception e) {
087                    LOG.error(e.getMessage(), e);
088                }
089            }
090        }
091        return matches;
092    }
093
094    private BooleanExpression getExpression(String selector) throws Exception{
095        BooleanExpression result;
096        synchronized(expressionCache){
097            result = expressionCache.get(selector);
098            if (result == null){
099                result = compileSelector(selector);
100                expressionCache.put(selector,result);
101            }
102        }
103        return result;
104    }
105
106    /**
107     * @return The SubQueueSelectorCacheBroker instance or null if no such broker is available.
108     */
109    private SubQueueSelectorCacheBroker getSubQueueSelectorCacheBrokerPlugin(final Broker broker) {
110        if (selectorCachePlugin == null) {
111            selectorCachePlugin = (SubQueueSelectorCacheBroker) broker.getAdaptor(SubQueueSelectorCacheBroker.class);
112        } //if
113
114        return selectorCachePlugin;
115    }
116
117    /**
118     * Pre-compile the JMS selector.
119     *
120     * @param selectorExpression The non-null JMS selector expression.
121     */
122    private BooleanExpression compileSelector(final String selectorExpression) throws Exception {
123        return SelectorParser.parse(selectorExpression);
124    }
125}