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.filter;
  
  import java.io.IOException;
  
  import org.apache.activemq.broker.region.MessageReference;
  import org.apache.activemq.command.ActiveMQDestination;
  import org.apache.activemq.command.Message;
  
  /**
   * MessageEvaluationContext is used to cache selection results. A message
   * usually has multiple selectors applied against it. Some selector have a high
   * cost of evaluating against the message. Those selectors may whish to cache
   * evaluation results associated with the message in the
   * MessageEvaluationContext.
   * 
   * 
   */
  public class MessageEvaluationContext {
  
  	protected MessageReference messageReference;
      protected boolean loaded;
      protected boolean dropped;
      protected Message message;
      protected ActiveMQDestination destination;
  
      public MessageEvaluationContext() {
      }
  
      public boolean isDropped() throws IOException {
          getMessage();
          return dropped;
      }
  
      public Message getMessage() throws IOException {
          if (!dropped && !loaded) {
              loaded = true;
              messageReference.incrementReferenceCount();
              message = messageReference.getMessage();
              if (message == null) {
                  messageReference.decrementReferenceCount();
                  dropped = true;
                  loaded = false;
              }
          }
          return message;
      }
  
      public void setMessageReference(MessageReference messageReference) {
          if (this.messageReference != messageReference) {
              clearMessageCache();
          }
          this.messageReference = messageReference;
      }
  
      public void clear() {
          clearMessageCache();
          destination = null;
      }
  
      public ActiveMQDestination getDestination() {
          return destination;
      }
  
      public void setDestination(ActiveMQDestination destination) {
          this.destination = destination;
      }
  
      /**
       * A strategy hook to allow per-message caches to be cleared
       */
      protected void clearMessageCache() {
          if (loaded) {
              messageReference.decrementReferenceCount();
          }
          message = null;
          dropped = false;
          loaded = false;
      }
  
      public MessageReference getMessageReference() {
          return messageReference;
      }
  }
  