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ActiveMQ example source code file (MessageEvaluationContext.java)

This example ActiveMQ source code file (MessageEvaluationContext.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

activemqdestination, activemqdestination, io, ioexception, ioexception, message, message, messageevaluationcontext, messageevaluationcontext, messagereference

The ActiveMQ MessageEvaluationContext.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.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;
    }
}

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