content: /**
   * 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.virtual;
  
  import org.apache.activemq.broker.Broker;
  import org.apache.activemq.broker.region.BaseDestination;
  import org.apache.activemq.broker.region.Destination;
  import org.apache.activemq.broker.region.Subscription;
  import org.apache.activemq.command.Message;
  import org.apache.activemq.filter.BooleanExpression;
  import org.apache.activemq.filter.MessageEvaluationContext;
  import org.apache.activemq.filter.NonCachedMessageEvaluationContext;
  import org.apache.activemq.plugin.SubQueueSelectorCacheBroker;
  import org.apache.activemq.selector.SelectorParser;
  import org.apache.activemq.util.LRUCache;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.Set;
  
  public class SelectorAwareVirtualTopicInterceptor extends VirtualTopicInterceptor {
      private static final Logger LOG = LoggerFactory.getLogger(SelectorAwareVirtualTopicInterceptor.class);
      LRUCache<String,BooleanExpression> expressionCache = new LRUCache<String,BooleanExpression>();
      private final SubQueueSelectorCacheBroker selectorCachePlugin;
  
      public SelectorAwareVirtualTopicInterceptor(Destination next, VirtualTopic virtualTopic) {
          super(next, virtualTopic);
          BaseDestination baseDestination = getBaseDestination(next);
          selectorCachePlugin = (SubQueueSelectorCacheBroker)
                  (baseDestination != null
                  ? baseDestination.createConnectionContext().getBroker().getAdaptor(SubQueueSelectorCacheBroker.class)
                  : null);
      }
  
      /**
       * Respect the selectors of the subscriptions to ensure only matched messages are dispatched to
       * the virtual queues, hence there is no build up of unmatched messages on these destinations
       */
      @Override
      protected boolean shouldDispatch(final Broker broker, Message message, Destination dest) throws IOException {
          //first validate that the prefix matches in the super class
          if (super.shouldDispatch(broker, message, dest)) {
              boolean matches = false;
              MessageEvaluationContext msgContext = new NonCachedMessageEvaluationContext();
              msgContext.setDestination(dest.getActiveMQDestination());
              msgContext.setMessageReference(message);
              List<Subscription> subs = dest.getConsumers();
              for (Subscription sub : subs) {
                  if (sub.matches(message, msgContext)) {
                      matches = true;
                      break;
                  }
              }
              if (matches == false) {
                  matches = tryMatchingCachedSubs(broker, dest, msgContext);
              }
              return matches;
          }
          return false;
      }
  
      private boolean tryMatchingCachedSubs(final Broker broker, Destination dest, MessageEvaluationContext msgContext) {
          boolean matches = false;
          LOG.debug("No active consumer match found. Will try cache if configured...");
  
          if (selectorCachePlugin != null) {
              final Set<String> selectors = selectorCachePlugin.getSelectorsForDestination(dest.getActiveMQDestination().getQualifiedName());
              if (selectors != null) {
                  for (String selector : selectors) {
                      try {
                          final BooleanExpression expression = getExpression(selector);
                          matches = expression.matches(msgContext);
                          if (matches) {
                              return true;
                          }
                      } catch (Exception e) {
                          LOG.error(e.getMessage(), e);
                      }
                  }
              }
          }
          return matches;
      }
  
      private BooleanExpression getExpression(String selector) throws Exception{
          BooleanExpression result;
          synchronized(expressionCache){
              result = expressionCache.get(selector);
              if (result == null){
                  result = compileSelector(selector);
                  expressionCache.put(selector,result);
              }
          }
          return result;
      }
  
      /**
       * Pre-compile the JMS selector.
       *
       * @param selectorExpression The non-null JMS selector expression.
       */
      private BooleanExpression compileSelector(final String selectorExpression) throws Exception {
          return SelectorParser.parse(selectorExpression);
      }
  }
  