Hi, what's the best practice for returning an arbi...

# http4k

[andyg]

Hi, what's the best practice for returning an arbitrary Map object as a JSON Response? No validation, as the keys will vary often. The 3 examples at https://www.http4k.org/guide/modules/json/ all describe objects specifically created to be JSON, not a normal Map (or list of Pairs). And can http4k automatically set the Response's content type to application/json? Perhaps an equivalent of Flask's jsonify (https://flask.palletsprojects.com/en/1.1.x/api/#flask.json.jsonify). Thanks.

[dave]

these both work depending on if you want to use lenses or not:

fun main() {
    val m = mapOf("too" to "bwob")
    println(Request(Method.GET, "").with(Body.auto<Map<String, Any>>().toLens() of m))
    println(Jackson.asJsonObject(m))
}

[andyg]

great, thanks, I was using the 2nd option, wasn't sure if that was considered best practice. Am I correct that only Jackson has asJsonObject, not Kotlinx or Moshi? And setting application/json must be done manually?

[dave]

anything that actually has a Json object API model will have that method. Moshi for example doesn't although it does the marshalling. Check out Json vs AutoMarshallingJson vs JsonLibAutoMarshallingJson

[dave]

KotlinX has a JsonElement class so does have that method

[dave]

If you want the content type to be set automatically then you'll need a lens - which means you'll need an implementation of AutoMarshallingJson

[andyg]

I don't mind setting Content-Type -- just want to be sure I am using Http4k efficiently

[dave]

My default is just to use Jackson with an auto lens.

[dave]

Then if you ever want to switch you can just switch out the Json implementation library and replace the imports

[dave]

(although TBH you probably wouldn't want to be Jackson is the one that plays best IMHO)

[andyg]

good to know, I started using moshi but had converted almost all my serialization to kotlinx

[andyg]

Thanks for the quick replies. Started working on my project again recently during lockdown. Have a couple of edge cases and scenarios, hope it's ok if I ask them on Slack

[dave]

of course! 🙂