kafka消息中间件Java API调用

参考: https://www.orchome.com/451

Kafka集群的安装见上文，本文介绍使用Java API通过kafka发送和接收消息。

 

1. kafka客户端依赖

    org.apache.kafka
    kafka_2.11
    1.0.1


    org.apache.kafka
    kafka-clients
    1.0.1

2 Kafka消息生产者API

package kafka;

import java.util.Properties;

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;

public class ProducerDemo {

    private static final String MY_TOPIC = "my-topic";

    public static void main(String[] args) {
        Properties properties = new Properties();

        // Kafka 服务器地址
        properties.put("bootstrap.servers", "127.0.0.1:9092,127.0.0.1:9093");

        // 消息应答机制
        properties.put("acks", "all");

        // 如果请求失败，生产者会自动重试，我们指定是0次，如果启用重试，则会有重复消息的可能性
        properties.put("retries", 0);
        properties.put("batch.size", 16384);

        // 默认缓冲可立即发送，即便缓冲空间还没有满，但是，如果你想减少请求的数量，可以设置linger.ms大于0
        properties.put("linger.ms", 1);

        // 控制生产者可用的缓存总量，如果消息发送速度比其传输到服务器的快，将会耗尽这个缓存空间
        properties.put("buffer.memory", 33554432);

        // 消息序列化和反序列化方法
        properties.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        properties.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

        // 创建并发送消息
        try (Producer producer = new KafkaProducer<>(properties)) {
            for (int i = 0; i < 100; i++) {
                String msg = "Message-index-" + i;
                producer.send(new ProducerRecord<>(MY_TOPIC, msg));
                System.out.println("Sent: " + msg);
            }
        }
    }
}

消息发送结果:

 

3. Kafka消息消费者API

package kafka;

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;

import java.util.Collections;
import java.util.Properties;

public class ConsumerDemo {

    private static final String MY_TOPIC = "my-topic";

    public static void main(String[] args) {
        Properties properties = new Properties();

        // kafka 服务器地址
        properties.put("bootstrap.servers", "127.0.0.1:9092");

        // 当前消费者所在的consumer group
        properties.put("group.id", "group-1");

        // 消息消费后自动提交，也可改为手动提交
        properties.put("enable.auto.commit", true);

        // 自动提交间隔时间
        properties.put("auto.commit.interval.ms", "1000");
        properties.put("auto.offset.reset", "earliest");

        // 停止心跳的时间超过session.timeout.ms,那么就会认为是故障的，它的分区将被分配到别的进程
        properties.put("session.timeout.ms", "30000");
        
        // 消息序列化和反序列化方法
        properties.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        properties.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

        // 订阅 my-topic 主题的消息
        KafkaConsumer consumer = new KafkaConsumer<>(properties);
        consumer.subscribe(Collections.singletonList(MY_TOPIC));
        
        // 不停的获取消息并消费
        while (true) {
            ConsumerRecords records = consumer.poll(1000);
            System.out.println("records count: " + records.count());
            for (ConsumerRecord record : records) {
                System.out.printf("offset = %d, key = %s, value = %s", record.offset(), record.key(), record.value());
                System.out.println();
            }
        }
    }
}

消息消费的结果如下：