Spring Boot入门教程(二十四): Kafka

1. pom.xml

Kafka并没有提供对应的Starter，而是使用的spring-kafka

<dependency>
    <groupId>org.springframework.kafka</groupId>
    <artifactId>spring-kafka</artifactId>
</dependency>

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
</dependency>
<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.2</version>
</dependency>

2. application.properties

#============== kafka ===================
# 指定kafka 代理地址，可以多个
spring.kafka.bootstrap-servers=localhost:9092

#=============== provider  =======================

spring.kafka.producer.retries=0
# 每次批量发送消息的数量
spring.kafka.producer.batch-size=16384
spring.kafka.producer.buffer-memory=33554432

# 指定消息key和消息体的编解码方式
spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.producer.value-serializer=org.apache.kafka.common.serialization.StringSerializer

#=============== consumer  =======================
# 指定默认消费者group id
spring.kafka.consumer.group-id=test-consumer-group

spring.kafka.consumer.auto-offset-reset=earliest
spring.kafka.consumer.enable-auto-commit=true
spring.kafka.consumer.auto-commit-interval=100

# 指定消息key和消息体的编解码方式
spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
spring.kafka.consumer.value-deserializer=org.apache.kafka.common.serialization.StringDeserializer

3. KafkaTemplate

Kafka使用KafkaTemplate发送消息，使用@KafkaListener消费指定主题的消息。

@Data
@AllArgsConstructor
public class Message {
    private String id;       // id
    private String msg;      // 消息
    private Long timestamp;  // 时间戳
}

生产消息(发送消息)

@RunWith(SpringRunner.class)
@SpringBootTest
public class KafkaApplicationTests {

    @Autowired
    private KafkaTemplate<String, String> kafkaTemplate;

    @Test
    public void testKafka() throws Exception{
        Gson gson = new GsonBuilder().create();
        String topic = "topic1";
        for (int i = 0; i < 3; i ++) {
            String key = "key-" + i;
            Message data = new Message(UUID.randomUUID().toString(), "hello kafka: " + i, new Date().getTime());

            // 默认情况下，如果主题不存在会自动帮你创建注意，是否允许创建不存在的主题可以在kafka中配置
            kafkaTemplate.send(topic, key, gson.toJson(data));
            Thread.sleep(1000);
        }
    }
}

消费消息(接收消息)

@Component
public class KafkaListener {
    public static Logger logger = LoggerFactory.getLogger(KafkaListener.class);

    @org.springframework.kafka.annotation.KafkaListener(topics = {"topic1", "topic2"})
    public void listenerForTopic1(ConsumerRecord<?, ?> record) {
        logger.info("topic={}  key={} value={}", record.topic(), record.key(), record.value());
    }
}

4. 启动kafka

# 首先启动zookeeper
cd /usr/local/Cellar/kafka/1.0.0
./bin/zookeeper-server-start /usr/local/etc/kafka/zookeeper.properties

# 再启动kafka
cd /usr/local/Cellar/kafka/1.0.0
./bin/kafka-server-start /usr/local/etc/kafka/server.properties

5. test