如何在kafka中创建自定义序列化器？

Question

只有少数可用的序列化器，如

org.apache.kafka.common.serialization.StringSerializer

我们如何创建自己的自定义序列化程序？

Answer 1

您必须创建自己的实现接口 Serializer (org.apache.kafka.common.serialization.Serializer) 的序列化程序，然后为其设置生产者选项 key.serializer / value.serializer。

Answer 2

这里有一个使用您自己的 serializer/deserializer 作为 Kafka 消息值的示例。对于 Kafka 消息密钥是一样的。

我们想发送 MyMessage 的序列化版本作为 Kafka 值，并在消费者端再次将其反序列化为 MyMessage 对象。

在生产者端序列化 MyMessage。

您应该创建一个实现 org.apache.kafka.common.serialization.Serializer

的序列化程序 class

serialize() 方法完成工作，接收您的对象并将序列化版本作为字节数组返回。

public class MyValueSerializer implements Serializer<MyMessage>
{
    private boolean isKey;

    @Override
    public void configure(Map<String, ?> configs, boolean isKey)
    {
        this.isKey = isKey;
    }

    @Override
    public byte[] serialize(String topic, MyMessage message)
    {
        if (message == null) {
            return null;
        }

        try {

            (serialize your MyMessage object into bytes)

            return bytes;

        } catch (IOException | RuntimeException e) {
            throw new SerializationException("Error serializing value", e);
        }
    }

    @Override
    public void close()
    {

    }
}

final IntegerSerializer keySerializer = new IntegerSerializer();
final MyValueSerializer myValueSerializer = new MyValueSerializer();
final KafkaProducer<Integer, MyMessage> producer = new KafkaProducer<>(props, keySerializer, myValueSerializer);

int messageNo = 1;
int kafkaKey = messageNo;
MyMessage kafkaValue = new MyMessage();
ProducerRecord producerRecord = new ProducerRecord<>(topic, kafkaKey, kafkaValue);
producer.send(producerRecord, new DemoCallBack(logTag, startTime, messageNo, strValue));

在消费者端反序列化 MyMessage。

您应该创建一个实现 org.apache.kafka.common.serialization.Deserializer

的反序列化器 class

deserialize() 方法完成工作，接收序列化值作为字节数组并返回您的对象。

public class MyValueDeserializer implements Deserializer<MyMessage>
{
    private boolean isKey;

    @Override
    public void configure(Map<String, ?> configs, boolean isKey)
    {
        this.isKey = isKey;
    }

    @Override
    public MyMessage deserialize(String s, byte[] value)
    {
        if (value == null) {
            return null;
        }

        try {

            (deserialize value into your MyMessage object)

            MyMessage message = new MyMessage();
            return message;

        } catch (IOException | RuntimeException e) {
            throw new SerializationException("Error deserializing value", e);
        }
    }

    @Override
    public void close()
    {

    }
}

然后像这样使用它：

final IntegerDeserializer keyDeserializer = new IntegerDeserializer();
final MyValueDeserializer myValueDeserializer = new MyValueDeserializer();
final KafkaConsumer<Integer, MyMessage> consumer = new KafkaConsumer<>(props, keyDeserializer, myValueDeserializer);

ConsumerRecords<Integer, MyMessage> records = consumer.poll(1000);
for (ConsumerRecord<Integer, MyMessage> record : records) {

    int kafkaKey = record.key();
    MyMessage kafkaValue = record.value();

    ...
}

Answer 3

没有文字，只有代码

你发送给 Kafka 的一些对象

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class TestDto {

    private String name;
    private String version;

}

创建Serializer，Producer会用到

@Slf4j
public class KafkaValueSerializer implements Serializer<TestDto> {

    private ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public void configure(Map<String, ?> configs, boolean isKey) {
    }

    @Override
    public byte[] serialize(String topic, TestDto data) {
        try {
            return objectMapper.writeValueAsBytes(data);
        } catch (JsonProcessingException e) {
            log.error("Unable to serialize object {}", data, e);
            return null;
        }
    }

    @Override
    public void close() {
    }
}

当然，不要忘记消费者的反序列化器

@Slf4j
public class KafkaValueDeserializer implements Deserializer<TestDto> {

    private ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public void configure(Map<String, ?> configs, boolean isKey) {
    }

    @Override
    public TestDto deserialize(String topic, byte[] data) {
        try {
            return objectMapper.readValue(new String(data, "UTF-8"), TestDto.class);
        } catch (Exception e) {
            log.error("Unable to deserialize message {}", data, e);
            return null;
        }
    }

    @Override
    public void close() {
    }
}

最后一刻，加serializer/deserializer到application.yml

spring:
    kafka:
      bootstrap-servers:  192.168.192.168:9092
      producer:
          value-serializer: com.package.service.kafka.KafkaValueSerializer
      consumer:
          group-id: groupId
          value-deserializer: com.package.service.kafka.KafkaValueDeserializer

就是这样。不需要任何配置文件或手鼓跳舞:)

发送

KafkaTemplate<String, TestDto> kafkaTemplate;

TestDto test = new TestDto("test name", "test-version");
kafkaTemplate.send(topic, testDto);

听

@KafkaListener(topics = "${ktp-agent.kafka.request-topic}", groupId = "${spring.kafka.consumer.group-id}")
public void listen(TestDto message) {

    log.info("Received message '{}' from Kafka.", message.toString());
}

如何在kafka中创建自定义序列化器？

How to create Custom serializer in kafka?

java

apache-kafka

kafka-producer-api