Hi, getting started with http4k and have some troubles understanding some concepts. I try poking around but got stuck here. I want to get the code from a from posted:

val codeField = FormField.required("code")
        val pageForm = Body
                .webForm(Validator.Strict, codeField)
                .toLens()

        val validForm = pageForm(request)
        val code = codeField(validForm)

but when I call the api from a static JS fetch request I get a 500 error:

org.http4k.lens.LensFailure: header 'content-type' is not acceptable

for the last line of code. Why does it check the content-type header if it's a Body lens ? And how to get around with it ? the JS fetch request is:

fetch{"/check", {
  method: "post",
  body: "code=XXXX"
})

tried with FormData and multipart got the same error.

The body lens will expect the content type to be set to "application/x-www-form-urlencoded"

Thank you... I've already tried with specifying the content type, but the site from which I copied called it

application/x-www-form-url-encoded

and that didn't work (lucky me to have found the one site that misspelled the content type). But removing the

-

from

url-encoded

fixed it. I was using CatchAll thought it included LensFailures ones.

Catchall just stops an exception from.bubbling out to the server layer. If you want to hide the stacktrace from the client (good practice) this should also be configured as such.

Yes it's true is not great message the stacktrace as error. (can help in dev). Changed to CatchLensFailure. Again thanks for your help and thanks for the great library... Quite impressed with the quality and the number of things it supports/does. The down side is that as an inexperienced functional programming dev I feel overwhelmed by some concepts and the right way to use them between the doc, site examples and realword one not easy to turn around... It's great to have this place to ask them.

If you ever come across something that you don't know how to use, can also recommend checking out the tests in GitHub.