external/storm-jms/src/main/java/org/apache/storm/jms/JmsTupleProducer.java

/**
 * 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.storm.jms;

import java.io.Serializable;
import javax.jms.JMSException;
import javax.jms.Message;
import org.apache.storm.topology.OutputFieldsDeclarer;
import org.apache.storm.tuple.Values;

/**
 * Interface to define classes that can produce a Storm <code>Values</code> objects
 * from a <code>javax.jms.Message</code> object>.
 *
 * <p>Implementations are also responsible for declaring the output
 * fields they produce.
 *
 * <p>If for some reason the implementation can't process a message
 * (for example if it received a <code>javax.jms.ObjectMessage</code>
 * when it was expecting a <code>javax.jms.TextMessage</code> it should
 * return <code>null</code> to indicate to the <code>JmsSpout</code> that
 * the message could not be processed.
 *
 */
public interface JmsTupleProducer extends Serializable {
    /**
     * Process a JMS message object to create a Values object.
     *
     * @param msg - the JMS message
     * @return the Values tuple, or null if the message couldn't be processed.
     */
    Values toTuple(Message msg) throws JMSException;

    /**
     * Declare the output fields produced by this JmsTupleProducer.
     *
     * @param declarer The OuputFieldsDeclarer for the spout.
     */
    void declareOutputFields(OutputFieldsDeclarer declarer);
}