This could be more a JVM ecosystem question than K...

# getting-started

[Larry Garfield]

This could be more a JVM ecosystem question than Kotlin specifically… I have this code:

val body = objectMapper.writeValueAsString(error)
val request = HttpEntity<String>(body, headers)
restTemplate.exchange(uri, HttpMethod.POST, request)

I just want to send a postback message to an endpoint. I do not care about the response at all. However, RestTemplate.exchange() insists on a 4th argument that is the class name to cast the response into. Is there an alternate approach for when I don’t know or care what comes back, I just want to send-and-forget? (This is in SpringBoot, but I’m not sure if that matters. Still new to the ecosystem and not sure where the lines are.)

[Youssef Shoaib [MOD]]

I mean if you pass in the class Any (or Object in Java) then it should always succeed

[Larry Garfield]

Hm.

restTemplate.exchange(uri, <http://HttpMethod.POST|HttpMethod.POST>, request, Any::class.java)

That at least keeps my IDE happy. I feel like I’m probably not doing this optimally, but I guess it works?

[Youssef Shoaib [MOD]]

That's the right way to do it I'd say. You could define an extension method to do this for you:

fun RestTemplate.exchangeAndForget(uri: Uri, method: HttpMethod, request: HttpEntity) {
  exchange(uri, method, request, Any::class.java)
}

[Youssef Shoaib [MOD]]

Or you could go the extra mile and create a nicer exchange method using Kotlin's reified types:

inline fun <reified T> RestTemplate.exchange(uri: Uri, method: HttpMethod, request: HttpEntity): T =
  exchange(uri, method, request, T::class.java)

and then when you don't care about the result you can simply do restTemplate.exchange<Any?>(uri, <http://HttpMethod.POST|HttpMethod.POST>, request), and when you care about the result, then you can use the right type

[Riccardo Lippolis]

Kotlin extension methods for RestTemplate are already present in the spring-web library. The Kotlinified exchange method that @Youssef Shoaib [MOD] mentioned above is available, see: https://github.com/spring-projects/spring-framework/blob/93387e69b53620b13b379bd972a18cdc3fd54be7/spring-web/src/main/kotlin/org/springframework/web/client/RestOperationsExtensions.kt#L275

Which means you could already write it as follows, as long as you (let IntelliJ) add the necessary import:

import org.springframework.web.client.exchange

// ...

restTemplate.exchange<Any?>(uri, HttpMethod.POST, request)

[Larry Garfield]

Huh. OK then. It’s not worth building my own extension wrapper for this use case, but if Spring already has one, I’ll just use that. Thanks.