jawn-fs2

Asynchronously parse fs2 streams to JSON values with jawn.

Example

sbt jawn-fs2JVM/Test/run to see it in action:

package com.example

import cats.effect.{IO, IOApp, ExitCode}
import fs2.{io, text, Stream}
import fs2.io.file.Files
import java.nio.file.Paths
import jawnfs2._
import scala.concurrent.duration._

object Example extends IOApp {
  // Pick your favorite supported AST (e.g., json4s, argonaut, etc.)
  implicit val facade = org.typelevel.jawn.ast.JawnFacade

  def run(args: List[String]) = {
    // From JSON on disk
    val jsonStream = Files[IO].readAll(Paths.get("testdata/random.json"), 64)
    // Simulate lag between chunks
    val lag = Stream.awakeEvery[IO](100.millis)
    val laggedStream = jsonStream.chunks.zipWith(lag)((chunk, _) => chunk)
    // Print each element of the JSON array as we read it
    val json = laggedStream.unwrapJsonArray
      .map(_.toString)
      .intersperse("\n")
      .through(text.utf8Encode)
    // run converts the stream into an IO, unsafeRunSync executes the IO for its effects
    json.through(io.stdout).compile.drain.as(ExitCode.Success)
  }
}

Migration note

In jawn-fs2-2.x, the root package changes from jawn.fs2 to org.typelevel.jawn.fs2.

Add jawn-fs2 to your project

Add to your build.sbt:

// For cats-effect-2
libraryDependencies += "org.http4s" %% "jawn-fs2" % "1.1.0"

// For cats-effect-3
libraryDependencies += "org.typelevel" %% "jawn-fs2" % "2.0.0"

// Pick your AST: https://github.com/non/jawn#supporting-external-asts-with-jawn
libraryDependencies += "org.typelevel" %% "jawn-ast" % "1.0.0"

Compatibility matrix

Stream Library	You need...	Status
fs2-3.x	"org.typelevel" %% "jawn-fs2" % "2.0.0"	stable
fs2-2.x	"org.http4s" %% "jawn-fs2" % "1.1.0"	stable
fs2-1.x	"org.http4s" %% "jawn-fs2" % "0.14.2"	EOL
fs2-0.10.x	"org.http4s" %% "jawn-fs2" % "0.12.2"	EOL
fs2-0.9.x	"org.http4s" %% "jawn-fs2" % "0.10.1"	EOL
scalaz-stream-0.8a	"org.http4s" %% "jawn-streamz" % "0.10.1a"	EOL
scalaz-stream-0.8.x	"org.http4s" %% "jawn-streamz" % "0.10.1"	EOL

The legacy scalaz-stream artifacts are on the jawn-streamz branch.