Java Kafka 簡單示例

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簡介

    Java kafka 簡單代碼示例

maven依賴配置

<!-- kafka -->
<dependency>
    <groupId>org.apache.kafka</groupId>
    <artifactId>kafka-clients</artifactId>
    <version>0.11.0.0</version>
</dependency>

kakfa生產和消費者生成

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

import java.util.*;

/**
 * @author lw1243925457
 */
public class KafkaUtil {

    public static KafkaConsumer<String, String> createConsumer(String servers, String topic) {
        Properties properties = new Properties();
        properties.put("bootstrap.servers", servers);
        properties.put("group.id", "group-1");
        properties.put("enable.auto.commit", "false");
        properties.put("auto.commit.interval.ms", "1000");
        properties.put("auto.offset.reset", "earliest");
        properties.put("session.timeout.ms", "30000");
        properties.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        properties.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

        KafkaConsumer<String, String> kafkaConsumer = new KafkaConsumer<String, String>(properties);
        kafkaConsumer.subscribe(Arrays.asList(topic));
        return kafkaConsumer;
    }

    public static void readMessage(KafkaConsumer<String, String> kafkaConsumer, int timeout) {
        while (true) {
            ConsumerRecords<String, String> records = kafkaConsumer.poll(timeout);
            for (ConsumerRecord<String, String> record : records) {
                String value = record.value();
                kafkaConsumer.commitAsync();
                System.out.println(value);
            }
        }
    }

    public static KafkaProducer<String, String> createProducer(String servers) {
        Properties properties = new Properties();
        properties.put("bootstrap.servers", servers);
        properties.put("acks", "all");
        properties.put("retries", 0);
        properties.put("batch.size", 16384);
        properties.put("linger.ms", 1);
        properties.put("buffer.memory", 33554432);
        properties.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        properties.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        return new KafkaProducer<String, String>(properties);
    }

    public static void send(KafkaProducer<String, String> producer, String topic, String message) {
        producer.send(new ProducerRecord<String, String>(topic, message));
    }
}

運行

public class Main {

    public static void main(String[] args) {
        String servers = "localhost:9092,localhost:9093,localhost:9094";
        String topic = "TestTopic";
        String message = "test";

        KafkaProducer<String, String> producer = KafkaUtil.createProducer(servers);
        KafkaUtil.send(producer, topic, message);

        KafkaConsumer<String, String> consumer = KafkaUtil.createConsumer(servers, topic);
        KafkaUtil.readMessage(consumer, 100);
    }
}

使用心得

總是讀取最老的消息

    可能是group-id的問題，新起一個group-id名稱

• earliest:當各分區下有已提交的offset時，從提交的offset開始消費；無提交的offset時，從頭開始消費
• latest:當各分區下有已提交的offset時，從提交的offset開始消費；無提交的offset時，消費新產生的該分區下的數據
• none:topic各分區都存在已提交的offset時，從offset后開始消費；只要有一個分區不存在已提交的offset，則拋出異常

參考鏈接

• java 實現kafka消息生產者和消費者
• kafka（三）—Kafka的Java代碼示例和配置說明
• Kafka - 偏移量提交
• Kafka系列（四）Kafka消費者：從Kafka中讀取數據
• Kafka auto.offset.reset值詳解