Message Queue for Apache Kafka:Use the default endpoint to send and subscribe to messages

import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.clients.producer.ProducerConfig;

public class KafkaConsumerDemo {

    public static void main(String args[]) {
        // Load the kafka.properties file. 
        Properties kafkaProperties =  JavaKafkaConfigurer.getKafkaProperties();

        Properties props = new Properties();
        // Specify an endpoint. Obtain the default endpoint of the corresponding instance in the Message Queue for Apache Kafka console. 
        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, kafkaProperties.getProperty("bootstrap.servers"));
        // Set the maximum interval between two consecutive polling cycles. 
        // The default interval is 30s. If the consumer does not return a heartbeat message within the interval, the broker determines that the consumer is not alive. In this case, the broker removes the consumer from the consumer group and triggers load balancing.Group 
        props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
        // Set the maximum number of messages that can be polled at a time. 
        // Do not set this parameter to an excessively large value. If the messages polled are not all consumed before the next polling cycle starts, load balancing is triggered and performance may deteriorate. 
        props.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, 30);
        // Set the method for deserializing messages. 
        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        // Specify the consumer group of the current consumer. You must create the consumer group in the Message Queue for Apache Kafka console. 
        // The consumers in a consumer group consume messages in load balancing mode. 
        props.put(ConsumerConfig.GROUP_ID_CONFIG, kafkaProperties.getProperty("group.id"));
        // Create a consumer object. 
        KafkaConsumer<String, String> consumer = new org.apache.kafka.clients.consumer.KafkaConsumer<String, String>(props);
        // Specify one or more topics to which the consumer group subscribes. 
        // We recommend that you configure consumers with the same GROUP_ID_CONFIG value to subscribe to the same topics. 
        List<String> subscribedTopics =  new ArrayList<String>();
        // If you want to subscribe to multiple topics, add the topics here. 
        // You must create the topics in the Message Queue for Apache Kafka console in advance. 
        String topicStr = kafkaProperties.getProperty("topic");
        String[] topics = topicStr.split(",");
        for (String topic: topics) {
            subscribedTopics.add(topic.trim());
        }
        consumer.subscribe(subscribedTopics);

        // Consume messages in a loop. 
        while (true){
            try {
                ConsumerRecords<String, String> records = consumer.poll(1000);
                // All messages must be consumed before the next polling cycle starts. The total duration cannot exceed the interval specified by SESSION_TIMEOUT_MS_CONFIG. 
                // We recommend that you create a separate thread pool to consume messages and then asynchronously return the results. 
                for (ConsumerRecord<String, String> record : records) {
                    System.out.println(String.format("Consume partition:%d offset:%d", record.partition(), record.offset()));
                }
            } catch (Exception e) {
                try {
                    Thread.sleep(1000);
                } catch (Throwable ignore) {

                }
                e.printStackTrace();
            }
        }
    }
}

import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.common.errors.WakeupException;

/**
 * This tutorial shows you how to use multiple consumers to simultaneously consume messages in one process. 
 * Make sure that the total number of consumers in the environment does not exceed the number of partitions of the topics to which the consumers subscribe. 
 */
public class KafkaMultiConsumerDemo {

    public static void main(String args[]) throws InterruptedException {
        // Load the kafka.properties file. 
        Properties kafkaProperties = JavaKafkaConfigurer.getKafkaProperties();

        Properties props = new Properties();
        // Specify an endpoint. Obtain the default endpoint of the corresponding instance in the Message Queue for Apache Kafka console. 
        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, kafkaProperties.getProperty("bootstrap.servers"));
        // Set the maximum interval between two consecutive polling cycles. 
        // The default interval is 30s. If the consumer does not return a heartbeat message within the interval, the broker determines that the consumer is not alive. In this case, the broker removes the consumer from the consumer group and triggers load balancing.Group 
        props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
        // Set the maximum number of messages that can be polled at a time. 
        // Do not set this parameter to an excessively large value. If the messages polled are not all consumed before the next polling cycle starts, load balancing is triggered and performance may deteriorate. 
        props.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, 30);
        // Set the method for deserializing messages. 
        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        // Specify the consumer group of the current consumer. You must create the consumer group in the Message Queue for Apache Kafka console. 
        // The consumers in a consumer group consume messages in load balancing mode. 
        props.put(ConsumerConfig.GROUP_ID_CONFIG, kafkaProperties.getProperty("group.id"));

        int consumerNum = 2;
        Thread[] consumerThreads = new Thread[consumerNum];
        for (int i = 0; i < consumerNum; i++) {
            KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);

            List<String> subscribedTopics = new ArrayList<String>();
            subscribedTopics.add(kafkaProperties.getProperty("topic"));
            consumer.subscribe(subscribedTopics);

            KafkaConsumerRunner kafkaConsumerRunner = new KafkaConsumerRunner(consumer);
            consumerThreads[i] = new Thread(kafkaConsumerRunner);
        }

        for (int i = 0; i < consumerNum; i++) {
            consumerThreads[i].start();
        }

        for (int i = 0; i < consumerNum; i++) {
            consumerThreads[i].join();
        }
    }

    static class KafkaConsumerRunner implements Runnable {
        private final AtomicBoolean closed = new AtomicBoolean(false);
        private final KafkaConsumer consumer;

        KafkaConsumerRunner(KafkaConsumer consumer) {
            this.consumer = consumer;
        }

        @Override
        public void run() {
            try {
                while (!closed.get()) {
                    try {
                        ConsumerRecords<String, String> records = consumer.poll(1000);
                        // All messages must be consumed before the next polling cycle starts. The total duration cannot exceed the interval specified by SESSION_TIMEOUT_MS_CONFIG. 
                        for (ConsumerRecord<String, String> record : records) {
                            System.out.println(String.format("Thread:%s Consume partition:%d offset:%d", Thread.currentThread().getName(), record.partition(), record.offset()));
                        }
                    } catch (Exception e) {
                        try {
                            Thread.sleep(1000);
                        } catch (Throwable ignore) {

                        }
                        e.printStackTrace();
                    }
                }
            } catch (WakeupException e) {
                // If the consumer is shut down, ignore the exception. 
                if (!closed.get()) {
                    throw e;
                }
            } finally {
                consumer.close();
            }
        }
        // Implement a shutdown hook that can be called by another thread. 
        public void shutdown() {
            closed.set(true);
            consumer.wakeup();
        }
    }
}