apache-kafka - spring-kafka 请求回复 : Different Types for Request and Reply

Question

提供 Request-Reply 支持的 ReplyingKafkaTemplate 文档(在 Spring-Kafka 2.1.3 中引入)表明请求和回复可以使用不同的类型:

ReplyingKafkaTemplate<K, V, R>

其中参数化类型 K 指定消息键，V 指定值(即请求)，R 指定回复。

到目前为止还不错。但是用于实现服务器端 Request-Reply 的相应支持类似乎不支持 V、R 的不同类型。文档建议使用带有添加的 @SendTo 注释的 KafkaListener，它在幕后使用 MessageListenerContainer 上配置的 replyTemplate .但是 AbstractKafkaListenerEndpoint 只支持单一类型的监听器以及 replyTemplate:

public abstract class AbstractKafkaListenerEndpoint<K, V>
        implements KafkaListenerEndpoint, BeanFactoryAware, InitializingBean {

    ...

    /**
     * Set the {@link KafkaTemplate} to use to send replies.
     * @param replyTemplate the template.
     * @since 2.0
     */
    public void setReplyTemplate(KafkaTemplate<K, V> replyTemplate) {
        this.replyTemplate = replyTemplate;
    }

    ...

}

因此 V 和 R 需要是同一类型。

文档中使用的示例确实对请求和回复都使用了字符串。

我是否遗漏了什么，或者这是应该报告和更正的 Spring-Kafka 请求-回复支持中的设计缺陷？

Answer 1

这是 fixed in the 2.2 release .

对于早期版本，只需注入(inject)一个原始的KafkaTemplate(没有泛型)。

编辑

@SpringBootApplication
public class So53151961Application {

    public static void main(String[] args) {
        SpringApplication.run(So53151961Application.class, args);
    }

    @KafkaListener(id = "so53151961", topics = "so53151961")
    @SendTo
    public Bar handle(Foo foo) {
        System.out.println(foo);
        return new Bar(foo.getValue().toUpperCase());
    }

    @Bean
    public ReplyingKafkaTemplate<String, Foo, Bar> replyingTemplate(ProducerFactory<String, Foo> pf,
            ConcurrentKafkaListenerContainerFactory<String, Bar> factory) {

        ConcurrentMessageListenerContainer<String, Bar> replyContainer =
                factory.createContainer("so53151961-replyTopic");
        replyContainer.getContainerProperties().setGroupId("so53151961.reply");
        ReplyingKafkaTemplate<String, Foo, Bar> replyingKafkaTemplate = new ReplyingKafkaTemplate<>(pf, replyContainer);
        return replyingKafkaTemplate;
    }

    @Bean
    public KafkaTemplate<String, Bar> replyTemplate(ProducerFactory<String, Bar> pf,
            ConcurrentKafkaListenerContainerFactory<String, Bar> factory) {

        KafkaTemplate<String, Bar> kafkaTemplate = new KafkaTemplate<>(pf);
        factory.setReplyTemplate(kafkaTemplate);
        return kafkaTemplate;
    }

    @Bean
    public ApplicationRunner runner(ReplyingKafkaTemplate<String, Foo, Bar> template) {
        return args -> {
            ProducerRecord<String, Foo> record = new ProducerRecord<>("so53151961", null, "key", new Foo("foo"));
            RequestReplyFuture<String, Foo, Bar> future = template.sendAndReceive(record);
            System.out.println(future.get(10, TimeUnit.SECONDS).value());
        };
    }

    @Bean
    public NewTopic topic() {
        return new NewTopic("so53151961", 1, (short) 1);
    }

    @Bean
    public NewTopic reply() {
        return new NewTopic("so53151961-replyTopic", 1, (short) 1);
    }

    public static class Foo {

        public String value;

        public Foo() {
            super();
        }

        public Foo(String value) {
            this.value = value;
        }

        public String getValue() {
            return this.value;
        }

        public void setValue(String value) {
            this.value = value;
        }

        @Override
        public String toString() {
            return "Foo [value=" + this.value + "]";
        }

    }

    public static class Bar {

        public String value;

        public Bar() {
            super();
        }

        public Bar(String value) {
            this.value = value;
        }

        public String getValue() {
            return this.value;
        }

        public void setValue(String value) {
            this.value = value;
        }

        @Override
        public String toString() {
            return "Bar [value=" + this.value + "]";
        }

    }

}

spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer
spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
spring.kafka.consumer.enable-auto-commit=false
spring.kafka.consumer.auto-offset-reset=earliest
spring.kafka.consumer.properties.spring.json.trusted.packages=com.example

结果

Foo [value=foo]
Bar [value=FOO]