java kafka 生产者消费者demo

一、修改kafka   server.porperties的ip是你本机的ip

listeners=PLAINTEXT://192.168.111.130:9092

二、生产者的例子

import org.apache.kafka.clients.producer.*;

import java.util.Properties;

public class KafkaProducerDemo {
    private final Producer<String, String> kafkaProdcer;
    public final static String TOPIC = "JAVA_TOPIC";

    private KafkaProducerDemo() {
        kafkaProdcer = createKafkaProducer();
    }

    private Producer<String, String> createKafkaProducer() {
        Properties props = new Properties();
        props.put("bootstrap.servers", "192.168.111.130:9092");
        props.put("acks", "all");
        props.put("retries", 0);
        props.put("batch.size", 16384);
        props.put("linger.ms", 1);
        props.put("buffer.memory", 33554432);
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        Producer<String, String> kafkaProducer = new KafkaProducer<String, String>(props);
        return kafkaProducer;
    }

    void produce() {
        for (int i = 0; i < 10; i++) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            final String key = "key" + i;
            String data = "hello kafka message:" + key;
            kafkaProdcer.send(new ProducerRecord<String, String>(TOPIC, key, data), new Callback() {
                public void onCompletion(RecordMetadata recordMetadata, Exception e) {
                    System.out.println("发送key" + key + "成功");
                }
            });
        }
    }

    public static void main(String[] args) {
        KafkaProducerDemo kafkaProducerDemo = new KafkaProducerDemo();
        kafkaProducerDemo.produce();
    }

}

用properties构造一个Producer的实例，然后调用send方法，传入数据，还有一个回调函数。

可以看到数据已经进来了。

三、消费者例子

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

import java.util.Arrays;
import java.util.Properties;

public class KafkaConsumerDemo {
    private final KafkaConsumer<String, String> consumer;
    private KafkaConsumerDemo(){
        Properties props = new Properties();
        props.put("bootstrap.servers", "192.168.111.130:9092");
        props.put("group.id", "test");
        props.put("enable.auto.commit", "false");
        props.put("auto.commit.interval.ms", "1000");
        props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        consumer = new KafkaConsumer<String, String>(props);
    }
    void consume(){
        consumer.subscribe(Arrays.asList(KafkaProducerDemo.TOPIC));
        while (true) {
            ConsumerRecords<String, String> records = consumer.poll(100);
            for (ConsumerRecord<String, String> record : records){
                System.out.println("I'm coming");
                System.out.printf("offset = %d, key = %s, value = %s%n", record.offset(), record.key(), record.value());
            }
        }
    }
    public static void main(String[] args) {
        KafkaConsumerDemo kafkaConsumerDemo = new KafkaConsumerDemo();
        kafkaConsumerDemo.consume();
    }
}

正常启动是看不到东西的， 两个同时启动才有。消费者只看接下来有哪些生产者发来新的消息。

props.put("enable.auto.commit", "true");

这个的意思是，消费后自动改变偏移量，就是会到最后。