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This module contains implementations of several components, connecting them to Kafka.

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/*
 * Copyright (c) 2010-2018. Axon Framework
 *
 * Licensed 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.axonframework.kafka.eventhandling;

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.axonframework.eventhandling.EventMessage;

import java.util.Optional;

/**
 * Converts Kafka Message from Axon Message and vice versa.
 *
 * @param  the key type.
 * @param  the value type.
 * @author Nakul Mishra
 * @since 3.0
 */
public interface KafkaMessageConverter {

    /**
     * Creates {@link ProducerRecord} for a given {@link EventMessage}
     *
     * @param eventMessage the event message to send to Kafka.
     * @param topic        the Kafka topic.
     * @return the record.
     */
    ProducerRecord createKafkaMessage(EventMessage eventMessage, String topic);

    /**
     * Reconstruct an EventMessage from the given  {@link ConsumerRecord}. The returned optional
     * resolves to a message if the given input parameters represented a correct {@link EventMessage}.
     *
     * @param consumerRecord Event message represented inside kafka
     * @return The Event Message to publish on the local event processors
     */
    Optional> readKafkaMessage(ConsumerRecord consumerRecord);
}