Hello World Example

Simple Example

zio-http-example/src/main/scala/example/HelloWorld.scala

//> using dep "dev.zio::zio-http:3.4.0"

package example

import zio._

import zio.http._

object HelloWorld extends ZIOAppDefault {
  // Responds with plain text
  val homeRoute =
    Method.GET / Root -> handler(Response.text("Hello World!"))

  // Responds with JSON
  val jsonRoute =
    Method.GET / "json" -> handler(Response.json("""{"greetings": "Hello World!"}"""))

  // Create HTTP route
  val app = Routes(homeRoute, jsonRoute)

  // Run it like any simple app
  override val run = Server.serve(app).provide(Server.default)
}

Advanced Example

zio-http-example/src/main/scala/example/HelloWorldAdvanced.scala

//> using dep "dev.zio::zio-http:3.4.0"

package example

import scala.util.Try

import zio._

import zio.http._
import zio.http.netty.NettyConfig
import zio.http.netty.NettyConfig.LeakDetectionLevel

object HelloWorldAdvanced extends ZIOAppDefault {
  // Set a port
  val PORT = 58080

  val fooBar =
    Routes(
      Method.GET / "foo" -> Handler.from(Response.text("bar")),
      Method.GET / "bar" -> Handler.from(Response.text("foo")),
    )

  val app = Routes(
    Method.GET / "random" -> handler(Random.nextString(10).map(Response.text(_))),
    Method.GET / "utc"    -> handler(Clock.currentDateTime.map(s => Response.text(s.toString))),
  )

  val run = ZIOAppArgs.getArgs.flatMap { args =>
    // Configure thread count using CLI
    val nThreads: Int = args.headOption.flatMap(x => Try(x.toInt).toOption).getOrElse(0)

    val config           = Server.Config.default
      .port(PORT)
    val nettyConfig      = NettyConfig.default
      .leakDetection(LeakDetectionLevel.PARANOID)
      .maxThreads(nThreads)
    val configLayer      = ZLayer.succeed(config)
    val nettyConfigLayer = ZLayer.succeed(nettyConfig)

    (fooBar ++ app)
      .serve[Any]
      .provide(configLayer, nettyConfigLayer, Server.customized)
  }
}

Advanced with CORS Example

zio-http-example/src/main/scala/example/HelloWorldWithCORS.scala

//> using dep "dev.zio::zio-http:3.4.0"

package example
import zio._

import zio.http.Header.{AccessControlAllowOrigin, Origin}
import zio.http.Middleware.{CorsConfig, cors}
import zio.http._
import zio.http.codec.PathCodec
import zio.http.template._

object HelloWorldWithCORS extends ZIOAppDefault {

  val config: CorsConfig =
    CorsConfig(
      allowedOrigin = {
        case origin if origin == Origin.parse("http://localhost:3000").toOption.get =>
          Some(AccessControlAllowOrigin.Specific(origin))
        case _                                                                      => None
      },
    )

  val backend: Routes[Any, Response] =
    Routes(
      Method.GET / "json" -> handler(Response.json("""{"message": "Hello World!"}""")),
    ) @@ cors(config)

  val frontend: Routes[Any, Response] =
    Routes(
      Method.GET / PathCodec.empty -> handler(
        Response.html(
          html(
            p("Message: ", output()),
            script("""
                     |// This runs on http://localhost:3000
                     |fetch("http://localhost:8080/json")
                     |  .then((res) => res.json())
                     |  .then((res) => document.querySelector("output").textContent = res.message);
                     |""".stripMargin),
          ),
        ),
      ),
    )

  val frontEndServer = Server.serve(frontend).provide(Server.defaultWithPort(3000))
  val backendServer  = Server.serve(backend).provide(Server.defaultWithPort(8080))

  val run = frontEndServer.zipPar(backendServer)
}

Advanced with Middlewares Example

zio-http-example/src/main/scala/example/HelloWorldWithMiddlewares.scala

//> using dep "dev.zio::zio-http:3.4.0"

package example

import java.util.concurrent.TimeUnit

import zio._

import zio.http._

object HelloWorldWithMiddlewares extends ZIOAppDefault {

  val routes: Routes[Any, Response] = Routes(
    // this will return result instantly
    Method.GET / "text"         -> handler(ZIO.succeed(Response.text("Hello World!"))),
    // this will return result after 5 seconds, so with 3 seconds timeout it will fail
    Method.GET / "long-running" -> handler(ZIO.succeed(Response.text("Hello World!")).delay(5 seconds)),
  )

  val serverTime = Middleware.patchZIO(_ =>
    for {
      currentMilliseconds <- Clock.currentTime(TimeUnit.MILLISECONDS)
      header = Response.Patch.addHeader("X-Time", currentMilliseconds.toString)
    } yield header,
  )
  val middlewares =
    // print debug info about request and response
    Middleware.debug ++
      // close connection if request takes more than 3 seconds
      Middleware.timeout(3 seconds) ++
      // add static header
      Middleware.addHeader("X-Environment", "Dev") ++
      // add dynamic header
      serverTime

  // Run it like any simple app
  val run = Server.serve(routes @@ middlewares).provide(Server.default)
}