Can I have a body lens which produces pretty formatted JSON (on server side)?

# http4k

[Mikael Ståldal]

Can I have a body lens which produces pretty formatted JSON (on server side)?

[Mikael Ståldal]

This seems to work (with GSON):

val prettyGson = GsonBuilder().setPrettyPrinting().create()
val prettyJsonBody = Body.string(ContentType.APPLICATION_JSON, "pretty JSON").map(
        {
            prettyGson.fromJson(it, JsonElement::class.java)
        },
        {
            prettyGson.toJson(it)
        }
).toLens()

[Mikael Ståldal]

There is a pretty thing here: https://github.com/http4k/http4k/blob/master/http4k-format/core/src/main/kotlin/org/http4k/format/Json.kt#L67
but I am not sure how it is supposed to be used 🤔

[s4nchez]

You can do it by creating a custom ConfigurableGson and using the auto from it. Here's a full example:

import CustomGson.auto
import com.google.gson.GsonBuilder
import org.http4k.core.Body
import org.http4k.core.Response
import org.http4k.core.Status.Companion.OK
import org.http4k.core.with
import org.http4k.format.ConfigurableGson
import org.http4k.format.asConfigurable
import org.http4k.format.withStandardMappings


data class MyDataClass(val foo: String, val bar: String)

fun main() {
    val lens = Body.auto<MyDataClass>().toLens()

    val response = Response(OK).with(lens of MyDataClass("foo", "bar"))

    println(response)
}

object CustomGson : ConfigurableGson(
    GsonBuilder()
        .setPrettyPrinting()
        .serializeNulls()
        .asConfigurable()
        .withStandardMappings()
        .done()
)

[s4nchez]

This prints:

HTTP/1.1 200 OK
content-type: application/json; charset=utf-8

{
  "foo": "foo",
  "bar": "bar"
}

[Mikael Ståldal]

Right. I only want this for some endpoints though, not all.

[s4nchez]

You can still do this with import aliases:

import CustomGson.auto as prettyAuto

(then use Body.prettyAuto to create the special lens)

[s4nchez]

You can then mix and match different Json Config

[dave]

Adding in pretty printing just for browser usage seems a bit odd. Maybe you could make it an option for the entire API so that you get pretty or compact for all endpoints when you configure your server? (ie. switch out the GSON instance)

[Andrew O'Hara]

Note: If you use a swagger UI, it will pretty-print the JSON for you, without having to customize marshallers