我是 Kafka Streams 和 Spring Cloud Stream 的新手，但在将集成相关代码移动到属性文件方面阅读了一些关于它的好东西，因此开发人员可以主要关注事物的业务逻辑方面。

在这里，我有我的简单应用程序类。

package com.some.events.consumer

import com.some.events.SomeEvent
import org.apache.kafka.streams.kstream.KStream
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.context.annotation.Bean
import java.util.function.Consumer

@SpringBootApplication
class ConsumerApplication {
    @Bean
    fun consume(): Consumer<KStream<String, SomeEvent>> {
        return Consumer { input -> input.foreach { key, value -> println("Key: $key, value: $value") } }
    }
}

fun main(args: Array<String>) {
    runApplication<ConsumerApplication>(*args)
}

我的application.yml文件如下。

spring:
  cloud:
    function:
      definition: consume
    stream:
      bindings:
        consume-in-0:
          destination: "some-event"
          group: "some-event"

我的依赖项build.gradle.kts定义如下（这里只包含相关的）。

extra["springCloudVersion"] = "2020.0.2"

dependencies {
    implementation("org.jetbrains.kotlin:kotlin-reflect")
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
    implementation("org.springframework.cloud:spring-cloud-stream")
    implementation("org.springframework.cloud:spring-cloud-stream-binder-kafka-streams")
    testImplementation("org.springframework.boot:spring-boot-starter-test")
}

dependencyManagement {
    imports {
        mavenBom("org.springframework.cloud:spring-cloud-dependencies:${property("springCloudVersion")}")
    }
}

当我运行应用程序时，出现以下异常。

org.springframework.context.ApplicationContextException: Failed to start bean 'streamsBuilderFactoryManager'; nested exception is org.springframework.kafka.KafkaException: Could not start stream: ; nested exception is java.lang.IllegalArgumentException: 'listener' cannot be null
    at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:181) ~[spring-context-5.3.5.jar:5.3.5]
    at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54) ~[spring-context-5.3.5.jar:5.3.5]
    at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356) ~[spring-context-5.3.5.jar:5.3.5]
    at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
    at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155) ~[spring-context-5.3.5.jar:5.3.5]
    at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123) ~[spring-context-5.3.5.jar:5.3.5]
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:935) ~[spring-context-5.3.5.jar:5.3.5]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:586) ~[spring-context-5.3.5.jar:5.3.5]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:769) ~[spring-boot-2.4.4.jar:2.4.4]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:761) ~[spring-boot-2.4.4.jar:2.4.4]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426) ~[spring-boot-2.4.4.jar:2.4.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:326) ~[spring-boot-2.4.4.jar:2.4.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1313) ~[spring-boot-2.4.4.jar:2.4.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1302) ~[spring-boot-2.4.4.jar:2.4.4]
    at com.some.events.consumer.ConsumerApplicationKt.main(ConsumerApplication.kt:22) ~[main/:na]
Caused by: org.springframework.kafka.KafkaException: Could not start stream: ; nested exception is java.lang.IllegalArgumentException: 'listener' cannot be null
    at org.springframework.cloud.stream.binder.kafka.streams.StreamsBuilderFactoryManager.start(StreamsBuilderFactoryManager.java:94) ~[spring-cloud-stream-binder-kafka-streams-3.1.2.jar:3.1.2]
    at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) ~[spring-context-5.3.5.jar:5.3.5]
    ... 14 common frames omitted
Caused by: java.lang.IllegalArgumentException: 'listener' cannot be null
    at org.springframework.util.Assert.notNull(Assert.java:201) ~[spring-core-5.3.5.jar:5.3.5]
    at org.springframework.kafka.config.StreamsBuilderFactoryBean.addListener(StreamsBuilderFactoryBean.java:268) ~[spring-kafka-2.6.7.jar:2.6.7]
    at org.springframework.cloud.stream.binder.kafka.streams.StreamsBuilderFactoryManager.start(StreamsBuilderFactoryManager.java:84) ~[spring-cloud-stream-binder-kafka-streams-3.1.2.jar:3.1.2]
    ... 15 common frames omitted


Process finished with exit code 1

请注意，我知道我需要配置 Serde 和 Avro 相关的东西（我将 Avro 用于事件架构），但问题是，流甚至不会运行。

有人可以指出我正确的方向吗？我尝试在谷歌上搜索此问题，但没有人发布过由“侦听器”引起的问题不能为空。谢谢！

回答