sciss / play-json-sealed

Automatic sealed traits JSON format for play-json-alone

Version Matrix


Build Status Maven Central


This project is meant as an extension for the Json.format macro in the JSON library of the play framework which generates automatic JSON serializers. It provides a new macro AutoFormat which supports sealed trait types and falls back to the original macro for other types.

It is released under the GNU Lesser General Public License v2.1+ and comes with absolutely no warranties. It might be submitted to Play at some point. To contact the author, send an email to contact at

requirements / installation

This project currently compiles against Scala 2.12, 2.11, 2.10 using sbt 0.13.

To use the library in your project:

"de.sciss" %% "play-json-sealed" % v

The current version v is "0.4.1", corresponding with play-json version 2.3.10 for Scala 2.10 and 2.11, the last to support Java 6 and 7. We are using play-json version 2.6.0-M1 as the only available version published for Scala 2.12, where Java 8 is already mandatory.


Please see the file


Examples are provided by way of test sources (sbt test). Basically you get a format via AutoFormat[A]. If that trait requires formats for other traits, you need to put their respective formats implicitly in scope, first. There are also a few useful formats in Formats:

  • FileFormat for
  • Tuple2Format for any Tuple2, given that its type parameters have implicit formats
  • VecFormat for a collection.immutable.IndexedSeq, given that its element type has an implicit format
  • OptionFormat for any Option - this was stupidly removed from Play-JSON in 2.4.x.

limitations and issues

  • Recursive types are not yet possible (see RecursiveTest).
  • There is a scoping issue. If you have object Foo { case class Bar(i: Int) }, then you need to import the Bar symbol for the macros to work. E.g. Json.format[Foo.Bar] fails, whereas import Foo.Bar; Json.format[Bar] works.