Spring Kotlin with Kafka utilizing @SendTo does not properly work with Springs- Kotlin property substitution

[meshpaul]

🐞 Bug report

Hi,

While working with Spring Boot, Kotlin, Spring Kafka and utilizing Springs Request Reply template

kotlinVersion = '1.2.61'
springBootVersion = '2.0.5.RELEASE'
springCloudVersion = 'Greenwich.BUILD-SNAPSHOT'
gsonVersion = '2.8.5'
commonsValidatorVersion = '1.4.1'
libphonenumberVersion = '5.5'
log4jVersion = '2.11.1'
junitVersion = '4.12'
protobufGradlePluginVersion = '0.8.6'
springKafkaVersion = '2.1.10.RELEASE'
commonsValidatorVersion = '1.4.1'
jacksonModuleKotlinVersion = '2.9.6'
javaVersion='1.8'
I have stumbled upon an issue here is scenario thats easily replicated

Using Spring KafkaRequestReplyTemplate set up a required client call to REQ/REPLY topics
Using Listener to receive required messages on REQ topic and once received send them to REPLY topic via @sendto the value in @sendto is as follows
@KafkaListener(topics = ["${my.input-request-topic}"])
@sendto("${my.output-reply-topic}")
override fun caseRequestListener(myModel: CommandModel): CommandModel {
logger.warn("SUCCESS RECIVED MESSAGE {} ", myModel)

   myModel.responseType = CommandModel.ResponseType.SUCCESS

    return myModel

}

the above property definition in @sendto does not resolve and kept as is ${my.output-reply-topic}.

The only way this works if I use static declarations or change to use Spring EL using #{ and not Kotlin supported ${myVal}... I also tried git issue with custom property resolver that did not work... what works is something like this :
@sendto("#{systemProperties['my.output-response-topic'] ?: 'MY.CMD.CREATE.RESPONSE'}")

[garyrussell]

It's not just Kotlin - we don't currently resolve property placeholders at all.

[garyrussell]

The documentation clearly states what is supported iin @SendTo

The @sendto value can have several forms:

• @sendto("someTopic") routes to the literal topic
• @sendto("#{someExpression}") routes to the topic determined by evaluating the expression once during application context initialization.
• @sendto("!{someExpression}") routes to the topic determined by evaluating the expression at runtime. The #root object for the evaluation has 3 properties:
  • request - the inbound ConsumerRecord (or ConsumerRecords object for a batch listener))
  • source - the org.springframework.messaging.Message<?> converted from the request.
  • result - the method return result.
• @sendto (no properties) - this is treated as !{source.headers['kafka_replyTopic']} (since version 2.1.3).

What led you to believe property placeholders are supported?

(I am not saying we shouldn't support it, however).