查看“Kafka 的 Java 客户端-生产者的实现”的源代码

=== 1.生产者的基本实现 ===

* 引入依赖
<syntaxhighlight lang="xml">
    <dependencies>
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-clients</artifactId>
            <version>2.4.0</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.76</version>
        </dependency>
    </dependencies>
</syntaxhighlight>

* 具体实现
<syntaxhighlight lang="java">
package org.example.kafka;

import org.apache.kafka.clients.producer.*;
import org.apache.kafka.common.serialization.StringSerializer;

import java.util.Properties;
import java.util.concurrent.ExecutionException;

public class MySimpleProducer {

    private final static String TOPIC_NAME = "my-replicated-topic";

    public static void main(String[] args) throws ExecutionException, InterruptedException {

        //1.设置参数
        Properties props = new Properties();

        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "192.168.137.200:9092,192.168.137.200:9093,192.168.137.200:9094");

        //把发送的 key 从字符串序列化为字节数组
        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());

        //把发送消息 value 从字符串序列化为字节数组
        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());

        //2.创建生产消息的客户端，传入参数
        Producer<String, String> producer = new KafkaProducer<>(props);

        //3.创建消息
        //key：作用是决定往哪个分区上发，value：具体要发送的消息内容
        ProducerRecord<String, String> producerRecord = new ProducerRecord<>(TOPIC_NAME, "mykeyvalue", "helloKafka");

        //4.发送消息，得到消息发送的元数据并输出
        RecordMetadata metadata = producer.send(producerRecord).get();
        System.out.println("同步方式发送消息结果：" + "topic-" + metadata.topic() + "|partition-" + metadata.partition()
                + "|offset-" + metadata.offset());
    }

}
</syntaxhighlight>

=== 2.生产者的同步发送消息 ===
[[文件:生产者的同步发送消息.png|无|缩略图|900x900像素]]如果生产者发送消息没有收到 ack，生产者会阻塞，阻塞到3s的时间，如果还没有收到消息，会进行重试。重试的次数3次。<syntaxhighlight lang="java">
        //4.发送消息，得到消息发送的元数据并输出
        RecordMetadata metadata = producer.send(producerRecord).get();
        System.out.println("同步方式发送消息结果：" + "topic-" + metadata.topic() + "|partition-" + metadata.partition()
                + "|offset-" + metadata.offset());
</syntaxhighlight>

=== 3.生产者的异步发送消息 ===
[[文件:生产者的异步发送消息.png|无|缩略图|900x900像素]]
异步发送，生产者发送完消息后就可以执行之后的业务，broker 在收到消息后异步调用生产者提供的 callback 回调方法。<syntaxhighlight lang="java">
        //5.异步发送消息
        producer.send(producerRecord, new Callback() {
            @Override
            public void onCompletion(RecordMetadata metadata, Exception e) {
                if (e != null) {
                    System.out.println("发送消息失败：" + e.getStackTrace());
                }
                if (metadata != null) {
                    System.out.println("异步方式发送消息结果：" + "topic-" + metadata.topic() + "|partition-"
                            + metadata.partition() + "|offset-" + metadata.offset());
                }
            }
        });

        Thread.sleep(1000000L);
</syntaxhighlight>