examples/kafka/src/main/java/org/apache/camel/example/kafka/MessagePublisherClient.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
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package org.apache.camel.example.kafka;

import java.util.Calendar;
import java.util.HashMap;
import java.util.Map;

import org.apache.camel.CamelContext;
import org.apache.camel.ProducerTemplate;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.builder.component.ComponentsBuilderFactory;
import org.apache.camel.component.kafka.KafkaConstants;
import org.apache.camel.impl.DefaultCamelContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public final class MessagePublisherClient {

    private static final Logger LOG = LoggerFactory.getLogger(MessagePublisherClient.class);
    public static final String DIRECT_KAFKA_START = "direct:kafkaStart";
    public static final String DIRECT_KAFKA_START_WITH_PARTITIONER = "direct:kafkaStartWithPartitioner";
    public static final String HEADERS = "${headers}";

    private MessagePublisherClient() { }

    public static void main(String[] args) throws Exception {

        LOG.info("About to run Kafka-camel integration...");

        String testKafkaMessage = "Test Message from  MessagePublisherClient " + Calendar.getInstance().getTime();

        try (CamelContext camelContext = new DefaultCamelContext()) {

            // Add route to send messages to Kafka

            camelContext.addRoutes(new RouteBuilder() {
                public void configure() {
                    camelContext.getPropertiesComponent().setLocation("classpath:application.properties");

                    // setup kafka component with the brokers
                    ComponentsBuilderFactory.kafka()
                            .brokers("{{kafka.host}}:{{kafka.port}}")
                            .register(camelContext, "kafka");

                    from(DIRECT_KAFKA_START).routeId("DirectToKafka")
                            .to("kafka:{{producer.topic}}").log(HEADERS);

                    // Topic can be set in header as well.

                    from("direct:kafkaStartNoTopic").routeId("kafkaStartNoTopic")
                            .to("kafka:dummy")
                            .log(HEADERS);

                    // Use custom partitioner based on the key.

                    from(DIRECT_KAFKA_START_WITH_PARTITIONER).routeId("kafkaStartWithPartitioner")
                            .to("kafka:{{producer.topic}}?partitioner={{producer.partitioner}}")
                            .log(HEADERS);


                    // Takes input from the command line.

                    from("stream:in").setHeader(KafkaConstants.PARTITION_KEY, simple("0"))
                            .setHeader(KafkaConstants.KEY, simple("1")).to(DIRECT_KAFKA_START);

                }

            });

            try (ProducerTemplate producerTemplate = camelContext.createProducerTemplate()) {
                camelContext.start();

                Map<String, Object> headers = new HashMap<>();

                headers.put(KafkaConstants.PARTITION_KEY, 0);
                headers.put(KafkaConstants.KEY, "1");
                producerTemplate.sendBodyAndHeaders(DIRECT_KAFKA_START, testKafkaMessage, headers);

                // Send with topicName in header

                testKafkaMessage = "TOPIC " + testKafkaMessage;
                headers.put(KafkaConstants.KEY, "2");
                headers.put(KafkaConstants.TOPIC, "TestLog");

                producerTemplate.sendBodyAndHeaders("direct:kafkaStartNoTopic", testKafkaMessage, headers);

                testKafkaMessage = "PART 0 :  " + testKafkaMessage;
                Map<String, Object> newHeader = new HashMap<>();
                newHeader.put(KafkaConstants.KEY, "AB"); // This should go to partition 0

                producerTemplate.sendBodyAndHeaders(DIRECT_KAFKA_START_WITH_PARTITIONER, testKafkaMessage, newHeader);

                testKafkaMessage = "PART 1 :  " + testKafkaMessage;
                newHeader.put(KafkaConstants.KEY, "ABC"); // This should go to partition 1

                producerTemplate.sendBodyAndHeaders(DIRECT_KAFKA_START_WITH_PARTITIONER, testKafkaMessage, newHeader);
            }

            LOG.info("Successfully published event to Kafka.");
            System.out.println("Enter text on the line below : [Press Ctrl-C to exit.] ");

            Thread.sleep(5L * 60 * 1000);

            camelContext.stop();
        }
    }

}