Working with JSON¶
Json values are supported through codecs which encode/decode values to json strings. However, third-party libraries are needed for actual json parsing/printing. Currently, Circe, µPickle and Play JSON are supported.
Circe¶
To use Circe add the following dependency to your project:
"com.softwaremill.tapir" %% "tapir-json-circe" % "0.11.8"
Next, import the package (or extend the TapirJsonCirce
trait, see MyTapir):
import tapir.json.circe._
This will allow automatically deriving Codec
s which, given an in-scope circe Encoder
/Decoder
and a SchemaFor
,
will create a codec using the json media type. Circe includes a couple of approaches to generating encoders/decoders
(manual, semi-auto and auto), so you may choose whatever suits you.
Note that when using Circe’s auto derivation, any encoders/decoders for custom types must be in scope as well.
For example, to automatically generate a JSON codec for a case class:
import tapir._
import tapir.json.circe._
import io.circe.generic.auto._
case class Book(author: String, title: String, year: Int)
val bookInput: EndpointIO[Book] = jsonBody[Book]
Circe lets you select an instance of io.circe.Printer
to configure the way JSON objects are rendered. By default
Tapir uses Printer.nospaces
, which would render:
Json.obj(
"key1" -> Json.fromString("present"),
"key2" -> Json.Null
)
as
{"key1":"present","key2":null}
Suppose we would instead want to omit null
-values from the object and pretty-print it. You can configure this by
overriding the jsonPrinter
in tapir.circe.json.TapirJsonCirce
:
object MyTapirJsonCirce extends TapirJsonCirce {
override def jsonPrinter: Printer = Printer.spaces2.copy(dropNullValues = true)
}
import MyTapirJsonCirce._
Now the above JSON object will render as
{"key1":"present"}
µPickle¶
To use µPickle add the following dependency to your project:
"com.softwaremill.tapir" %% "tapir-json-upickle" % "0.11.8"
Next, import the package (or extend the TapirJsonuPickle
trait, see MyTapir and add TapirJsonuPickle
not TapirCirceJson
):
import tapir.json.upickle._
µPickle requires a ReadWriter in scope for each type you want to serialize. In order to provide one use the macroRW
macro in the companion object as follows:
import tapir._
import upickle.default._
import tapir.json.upickle._
case class Book(author: String, title: String, year: Int)
object Book {
implicit val rw: ReadWriter[Book] = macroRW
}
val bookInput: EndpointIO[Book] = jsonBody[Book]
Like Circe, µPickle allows you to control the rendered json output. Please see the Custom Configuration of the manual for details.
For more examples, including making a custom encoder/decoder, see TapirJsonuPickleTests.scala
Play JSON¶
To use Play JSON add the following dependency to your project:
"com.softwaremill.tapir" %% "tapir-json-play" % "0.11.8"
Next, import the package (or extend the TapirJsonPlay
trait, see MyTapir and add TapirJsonPlay
not TapirCirceJson
):
import tapir.json.play._
Play JSON requires Reads
and Writes
implicit values in scope for each type you want to serialize.
Other JSON libraries¶
To add support for additional JSON libraries, see the sources for the Circe codec (which is just a couple of lines of code).
Schemas¶
To derive json codecs automatically, not only implicits from the base library are needed (e.g. a circe
Encoder
/Decoder
), but also an implicit SchemaFor[T]
value, which provides a mapping between a type T
and its
schema. A schema-for value contains a single schema: Schema
field.
See custom types for details.
Next¶
Read on about working with forms.