Scala · Example Payload
Scala Cats Effect Http4S Example

Big DataDistributed SystemsFunctional ProgrammingJVMProgramming LanguageScalaScala 3Type Safety
Scala Cats Effect Http4S Example is an example object payload from Scala, with 1 top-level field. It illustrates the shape of data this provider's APIs accept or return.
Top-level fields

example
Example Payload

{
  "example": {
    "title": "http4s REST API with cats-effect — Scala 3",
    "description": "Example of a complete http4s HTTP server implementing a JSON REST API using cats-effect IO, circe for JSON encoding/decoding, and Scala 3 syntax.",
    "language": "scala",
    "scalaVersion": "3.4.2",
    "libraries": [
      { "name": "http4s-ember-server", "version": "0.23.27", "groupId": "org.http4s" },
      { "name": "http4s-circe", "version": "0.23.27", "groupId": "org.http4s" },
      { "name": "circe-generic", "version": "0.14.9", "groupId": "io.circe" },
      { "name": "cats-effect", "version": "3.5.4", "groupId": "org.typelevel" }
    ],
    "sbtDependencies": [
      "\"org.http4s\" %% \"http4s-ember-server\" % \"0.23.27\"",
      "\"org.http4s\" %% \"http4s-circe\" % \"0.23.27\"",
      "\"io.circe\" %% \"circe-generic\" % \"0.14.9\"",
      "\"org.typelevel\" %% \"cats-effect\" % \"3.5.4\""
    ],
    "code": {
      "file": "Main.scala",
      "content": [
        "import cats.effect.*",
        "import cats.syntax.all.*",
        "import io.circe.generic.auto.*",
        "import org.http4s.*",
        "import org.http4s.circe.CirceEntityCodec.*",
        "import org.http4s.dsl.io.*",
        "import org.http4s.ember.server.EmberServerBuilder",
        "import com.comcast.ip4s.*",
        "",
        "case class User(id: Long, name: String, email: String)",
        "case class CreateUserRequest(name: String, email: String)",
        "",
        "object Main extends IOApp.Simple:",
        "  val users = Map(",
        "    1L -> User(1L, \"Alice\", \"alice@example.com\"),",
        "    2L -> User(2L, \"Bob\", \"bob@example.com\")",
        "  )",
        "",
        "  val routes = HttpRoutes.of[IO] {",
        "    case GET -> Root / \"users\" =>",
        "      Ok(users.values.toList)",
        "",
        "    case GET -> Root / \"users\" / LongVar(id) =>",
        "      users.get(id).fold(NotFound())(user => Ok(user))",
        "",
        "    case req @ POST -> Root / \"users\" =>",
        "      for",
        "        body <- req.as[CreateUserRequest]",
        "        newId = users.keys.maxOption.getOrElse(0L) + 1",
        "        user = User(newId, body.name, body.email)",
        "        resp <- Created(user)",
        "      yield resp",
        "  }",
        "",
        "  val run =",
        "    EmberServerBuilder",
        "      .default[IO]",
        "      .withHost(ipv4\"0.0.0.0\")",
        "      .withPort(port\"8080\")",
        "      .withHttpApp(routes.orNotFound)",
        "      .build",
        "      .useForever"
      ]
    },
    "endpoints": [
      {
        "method": "GET",
        "path": "/users",
        "description": "List all users",
        "response": {
          "status": 200,
          "body": [
            { "id": 1, "name": "Alice", "email": "alice@example.com" },
            { "id": 2, "name": "Bob", "email": "bob@example.com" }
          ]
        }
      },
      {
        "method": "GET",
        "path": "/users/1",
        "description": "Get user by ID",
        "response": {
          "status": 200,
          "body": { "id": 1, "name": "Alice", "email": "alice@example.com" }
        }
      },
      {
        "method": "POST",
        "path": "/users",
        "description": "Create a new user",
        "requestBody": { "name": "Charlie", "email": "charlie@example.com" },
        "response": {
          "status": 201,
          "body": { "id": 3, "name": "Charlie", "email": "charlie@example.com" }
        }
      }
    ]
  }
}