Kafka客户端编程入门介绍

1.maven依赖

        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka_2.11</artifactId>
            <version>1.0.0</version>
        </dependency>

2.生产者

import org.apache.kafka.clients.producer.Callback;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;

import java.util.Properties;

/**
 * Created by zhangpeiran on 2018/9/30.
 */
public class MyProducer {
    private static  class DemoProducerCallback implements Callback{
        public void onCompletion(RecordMetadata recordMetadata,Exception e){
            if(e != null)
                e.printStackTrace();
            else
                System.out.print("send message success");
        }
    }

    public static void main(String[] args){
        Properties kafkaProps = new Properties();
        kafkaProps.put("bootstrap.servers","ip1:9092,ip2:9092");
        kafkaProps.put("key.serializer","org.apache.kafka.common.serialization.StringSerializer");
        kafkaProps.put("value.serializer","org.apache.kafka.common.serialization.StringSerializer");

        KafkaProducer producer = new KafkaProducer<String,String>(kafkaProps);

        ProducerRecord<String,String> record = new ProducerRecord<String, String>("DemoTopic","DemoKey","DemoValue");

        //async
        producer.send(record,new DemoProducerCallback());
        producer.close();
    }
}

3.自定义分区

import org.apache.kafka.clients.producer.Partitioner;
import org.apache.kafka.common.Cluster;
import org.apache.kafka.common.record.InvalidRecordException;
import org.apache.kafka.common.utils.Utils;

import java.util.Map;

/**
 * Created by zhangpeiran on 2018/10/8.
 */
public class MyPartitioner implements Partitioner {
    public void configure(Map<String,?> configs){}

    public void close(){}

    public int partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes, Cluster cluster) {
        if((keyBytes == null) || !(key instanceof String))
            throw new InvalidRecordException("Message should has a key");
        int numPartitions = cluster.partitionsForTopic(topic).size();
        return Math.abs(Utils.murmur2(keyBytes)) % numPartitions;
    }
}

需要在Producer中加入配置：

kafkaProps.put("partitioner.class","MyPartitioner");

4.消费者

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;

/**
 * Created by zhangpeiran on 2018/10/9.
 */
public class MyConsumer {

    public static void main(String[] args){
        Properties properties = new Properties();
        properties.put("bootstrap.servers","ip1:9092,ip2:9092,ip3:9092");
        properties.put("key.deserializer","org.apache.kafka.common.serialization.StringDeserializer");
        properties.put("value.deserializer","org.apache.kafka.common.serialization.StringDeserializer");
        properties.put("group.id","DemoConsumerGroup");

        //默认值为latest，当消费者读取的分区没有偏移量或偏移量无效时，消费者将从最新的记录开始读
        //当一个消费group第一次订阅主题时，符合这种情况，在Consumer启动之前，Producer生产的数据不会被读取
        //置为earliest，表示从分区起始位置读取消息
        properties.put("auto.offset.reset","earliest");

        KafkaConsumer<String,String> consumer = new KafkaConsumer<String, String>(properties);

        consumer.subscribe(Collections.singletonList("DemoTopic"));

        try {
            while (true){
                ConsumerRecords<String,String> records = consumer.poll(100);
                for(ConsumerRecord<String ,String> record : records){
                    System.out.print(record.topic() + "," + record.partition() + "," + record.offset() + "," + record.key() + "," + record.value());
                }
            }
        } finally {
            consumer.close();
        }
    }
}