Smithy4Play

smithy4play generates Play routes and controllers from your Smithy models using smithy4s. The example project smithy4playTest shows the current setup with Play 3, Scala 3.3.7, and smithy4s 0.18.46.

Quick start

1. Add sbt plugins

// project/plugins.sbt
addSbtPlugin("org.playframework" % "sbt-plugin" % "3.0.10")
addSbtPlugin("com.disneystreaming.smithy4s" % "smithy4s-sbt-codegen" % "0.18.46")

2. Enable plugins and dependencies

// build.sbt
lazy val myService = project
  .in(file("my-service"))
  .enablePlugins(Smithy4sCodegenPlugin, PlayScala)
  .settings(
    scalaVersion := "3.x.x",
    libraryDependencies ++= Seq(
      "de.innfactory" %% "smithy4play" % "0.5.0",
      "de.innfactory" %% "smithy4play-mcp" % "0.5.0"
    )
  )

3. Define your Smithy models (see smithy4playTest/testSpecs) and run sbt compile to generate service code under app/specs.

Routing

Auto-routing with MCP (recommended)

• Configure packages in conf/application.conf:
  • smithy4play.autoRoutePackage = "controller"
  • smithy4play.servicePackage = "your.namespace"
• Bind the router in conf/routes:

->      /                       controller.TestRouter

• Implement the router by extending AutoRouterWithMcp and optionally add middlewares:

@Singleton
class TestRouter @Inject() (implicit
  mcpController: McpController,
  cc: ControllerComponents,
  app: Application,
  ec: ExecutionContext,
  config: Config
) extends AutoRouterWithMcp {

  override def smithy4PlayMiddleware: Seq[Smithy4PlayMiddleware] =
    super.smithy4PlayMiddleware ++ Seq(ValidateAuthMiddleware(), AddHeaderMiddleware())
}

Manual binding

You can still wire controllers manually by extending BaseRouter and returning your controllers as Play Routes instances if you do not want auto-routing.

Implementing controllers

Extend the smithy4s-generated service trait with ContextRoute and mix in Controller to gain helpers:

@Singleton
class TestController @Inject() (implicit
  cc: ControllerComponents,
  ec: ExecutionContext,
  ws: WSClient
) extends TestControllerService[ContextRoute]
    with Controller {

  override def test(): ContextRoute[SimpleTestResponse] = Kleisli { _ =>
    EitherT.rightT[Future, Throwable](SimpleTestResponse(Some("ok")))
  }

  override def testWithOutput(
    pathParam: String,
    testQuery: String,
    testHeader: String,
    body: TestRequestBody
  ): ContextRoute[TestWithOutputResponse] = Kleisli { _ =>
    EitherT.rightT[Future, Throwable](TestWithOutputResponse(TestResponseBody(testHeader, pathParam, testQuery, body.message)))
  }
}

Middlewares

Register cross-cutting logic by extending Smithy4PlayMiddleware and appending it in your router:

@Singleton
class ValidateAuthMiddleware @Inject() (implicit ec: ExecutionContext) extends Smithy4PlayMiddleware {
  override def skipMiddleware(r: RoutingContext): Boolean = false

  override def logic(r: RoutingContext, next: RoutingContext => RoutingResult[Result]): RoutingResult[Result] =
    EitherT.leftT[Future, Result](UnauthorizedError("Unauthorized"))
}

MCP endpoints

The MCP module exposes smithy-defined tools. Implement them like any controller:

@Singleton
class McpTestController @Inject() (implicit cc: ControllerComponents, ec: ExecutionContext, ws: WSClient)
    extends McpControllerService[ContextRoute]
    with Controller {

  def reverseString(text: String, tagged: Option[TaggedTestUnion], untagged: Option[UntaggedTestUnion], discriminated: Option[DiscriminatedTestUnion]): ContextRoute[ReverseStringOutput] = Kleisli { _ =>
    val reversed = text.reverse
    EitherT.rightT[Future, Throwable](ReverseStringOutput(reversed, reversed.replaceAll("\\s", "").length * 2))
  }
}

Configuration reference

Key settings used in smithy4playTest/conf/application.conf:

smithy4play.autoRoutePackage = "controller"
smithy4play.servicePackage   = "testDefinitions.test"
play.http.parser.maxMemoryBuffer = 100MB
play.filters.enabled = []

Examples

• Full sample project: smithy4playTest
• Generated Smithy specs: smithy4playTest/testSpecs
• Controllers: smithy4playTest/app/controller
• Middlewares: smithy4playTest/app/controller/middlewares

For more, browse the sample code and run sbt test to execute the compliance tests.