Inclusion of spring-cloud-stream-binder-kafka.jar in classpath affects existing `@KafkaListener`s

[ilia1243]

Describe the issue
Inclusion of spring-cloud-stream-binder-kafka.jar in classpath changes properties of spring.kafka that affects existing @KafkaListeners.

The jar registers KafkaBinderEnvironmentPostProcessor that adds property source kafkaBinderDefaultProperties that in turn changes default properties of spring-kafka.

Is it possible to make introduction of the framework more safe in terms of impact on existing functionality?

Version of the framework 2024.0.1
Expected behavior Inclusion of the framework should not affect other frameworks.

[olegz]

I wonder if it is related to this recent commit - 899469a
Would you be able to try with 2024.0.0 and let me know or simply go to the previous commit, build and test?

We can certainly introduce a property to perform that "merge" (in that commit) optionally.

Anyway, let me know

[ilia1243]

Reproduced with 2024.0.0.

@SpringBootApplication
class Application

@Component
class TestConsumer {
    @KafkaListener(topics = ["test-topic"], groupId = "test-group")
    fun accept(record: ConsumerRecord<String?, String?>) {
        println("Received ${record.value()?.javaClass}")
    }
}

fun main() {
    runApplication<Application>()
}

application.yml:

spring:
  kafka:
    bootstrap-servers: localhost:9092

Dependencies:

plugins {
    kotlin("jvm") version "2.2.20"
    kotlin("plugin.spring") version "2.2.20"
}

repositories {
    mavenCentral()
}

dependencies {
    implementation(platform("org.springframework.boot:spring-boot-dependencies:3.4.6"))
    implementation(platform("org.springframework.cloud:spring-cloud-dependencies:2024.0.0"))
    implementation("org.springframework.boot:spring-boot-starter")
    implementation("org.springframework.kafka:spring-kafka")
    implementation("org.springframework.cloud:spring-cloud-stream-binder-kafka")
}

Exception: java.lang.ClassCastException: class [B cannot be cast to class java.lang.String

If remove dependency implementation("org.springframework.cloud:spring-cloud-stream-binder-kafka"). the message is received Received class java.lang.String.

[olegz]

Thank you, i'll upgrade it to a bug.
If you can it is better to provide reproducers as an independent project somewhere in guthub. This way we can react much quicker and it will allow you not to miss some important bits.