I m trying to convert a fork of a library from using Jackson

Question

I m trying to convert a fork of a library from using Jackson to using Kotlinx serialization I ve never used Jackson before Can anyone help me understand what this is doing ```objectMapper readValue lt Map lt String Any gt gt it ``` And how I might write it using Kotlinx serialization instead In the context it s extracting a JWT claim from a Json Web Token I don t know what the type of the Any is but I suspect it s just a String or possibly a List of Strings

Adam S · Answer

is `it` a string My guess is that the KxS equivalent is decoding to `JsonObject` <https github com Kotlin kotlinx serialization blob v1 4 1 docs json md json elements> you can try ```val jwtObj JsonObject = Json decodeFromString it ``` And then you can treat `JsonObject` like a key value Map

v79 · Answer

Yes `it` is a String I ll try that thanks

v79 · Answer

Next problem is ```response body let type of it is T amp Any whatever that means objectMapper writeValueAsString it ``` I guess that Jackson is using reflection so can find out what the concrete class of `T` is but kotlinx is not and I need to pass a SerializationStrategy and since it s `T` I don t know what type that is

Adam S · Answer

I d need a bit more context to figure that one out

Adam S · Answer

I think `T amp Any` means <https github com Kotlin KEEP blob c72601cf35c1e95a541bb4b230edb474a6d1d1a8 proposals definitely non nullable types md|definitely not null>

v79 · Answer

The entire function call is ```open fun lt T gt createResponse contentType MediaType response ResponseEntity lt T gt APIGatewayProxyResponseEvent = when response body = null amp amp serializationHandlerChain supports contentType response body true gt contentType false gt MediaType parse router defaultContentType let finalContentType gt APIGatewayProxyResponseEvent withStatusCode response statusCode withHeaders response headers toMutableMap apply put Content Type finalContentType toString withBody response body let Json encodeToString it serializationHandlerChain serialize finalContentType it as Any ``` The call to `serializationHandlerChain serialize finalContentType it as Any ` ultimately just ends with `objectMapper writeValueAsString body ` I can t just write `Json encodeToString it as Any `

Adam S · Answer

this is Spring Boot

v79 · Answer

No not at all It s <https github com moia oss lambda kotlin request router> for AWS Lambda functions written in Kotlin It s just a router

v79 · Answer

I had some issues with the library as it stands so I m experimenting with a fork for my own wee project

v79 · Answer

I have also experimented with writing my own router but I m not that clever

Adam S · Answer

the first thought that comes to mind is to make the function inline and T reified ```inline fun lt reified T gt createResponse ``` but I don t think that will work because it s `open` and it s probably too large complicated to inline

Adam S · Answer

I think probably the best is to add the Serializer into the `data class ResponseEntity`

Adam S · Answer

maybe ```data class ResponseEntity lt T gt val statusCode Int val body T = null val headers Map lt String String gt = emptyMap val serializer KSerializer lt T gt ```

Adam S · Answer

if you made the helper functions `inline` and `reified T` then I think you could get the `KSerializer lt T gt ` from the `SerializerModule` maybe

v79 · Answer

A lot of changes required I fear

v79 · Answer

All because I ve got some `LocalDate` values to deal with disappointed

Adam S · Answer

v79 · Answer

Yeah I ve done it myself Just a lot of changes to even get the tests to compile just now

Adam S · Answer

yeah