尝试使用ZIO库学习，所以我决定创建一个基本的web服务应用程序。想法很基本，使用http4slib作为服务器和路由端点，在端点调用上打印"helloworld"。
在我发现的文档和示例的帮助下，生成代码：
object Main extends ManagedApp {
type AppEnvironment = Clock with Console with HelloRepository
type AppTask[A] = RIO[AppEnvironment, A]
override def run(args: List[String]): ZManaged[ZEnv, Nothing, Int] = {
val httpApp: HttpApp[AppTask] = Router[AppTask]("/" -> helloWorldService).orNotFound
val server = ZIO.runtime[AppEnvironment].flatMap { implicit rts =>
BlazeServerBuilder[AppTask]
.bindHttp(8080, "0.0.0.0")
.withHttpApp(CORS(httpApp))
.serve
.compile[AppTask, AppTask, ExitCode]
.drain
}
(for {
_ <- ZManaged.environment[ZEnv] >>> server.toManaged_
} yield ())
.foldM(err => putStrLn(s"Execution failed with: $err").as(1).toManaged_, _ => ZManaged.succeed(0))
}
val dsl: Http4sDsl[AppTask] = Http4sDsl[AppTask]
import dsl._
val helloWorldService: HttpRoutes[AppTask] = HttpRoutes.of[AppTask] {
case GET -> Root / "hello" / name => Ok(Repo.getHello(name))
}
}
trait HelloRepository extends Serializable {
val helloRepository: HelloRepository.Service[Any]
}
object HelloRepository extends Serializable {
trait Service[R] extends Serializable {
def getHello(name: String): ZIO[R, Nothing, String]
}
}
object Repo extends HelloRepository.Service[HelloRepository] {
override def getHello(name: String): ZIO[HelloRepository, Nothing, String] = ZIO.succeed(s"Hello $name")
}
- 我创建路由器：
Router[AppTask]("/" ... - 我创建服务器：
ZIO.runtime[AppEnvironment].flatMap ... - 然后尝试用ZIO环境启动服务器，但我缺少的是这句话：
_ <- ZManaged.environment[ZEnv] >>> server.toManaged_不正确，并在生成时引发错误：错误：(34，39(推断的类型参数[touch.Main.AppEnvironment，Throwable，Unit]不符合方法>>的类型参数边界[R1>：zio.ZEnv，E1，B]_<-ZManaged.environment[ZEnv]>>server.toManaged_
Error:(34, 39) inferred type arguments [touch.Main.AppEnvironment,Throwable,Unit] do not conform to method >>>'s type parameter bounds [R1 >: zio.ZEnv,E1,B]
Error:(34, 50) type mismatch;
found : zio.ZManaged[touch.Main.AppEnvironment,Throwable,Unit]
(which expands to) zio.ZManaged[zio.clock.Clock with zio.console.Console with touch.HelloRepository,Throwable,Unit]
required: zio.ZManaged[R1,E1,B]
也许有人能帮我掌握正确的语法？还将提供一些解释，或链接到文档，在文档中对此进行解释。
我想解释更多，但我不知道你的代码示例是从哪里得到的，也不知道build.sbt是什么样子的，但我碰巧有一些http4s代码，所以我随意添加了一些import语句并对其进行了一点简化。你总是可以把我去掉的复杂性加回来。
以下是对我有效的方法。
/tmp/http4s/test.scala
import org.http4s.implicits._
import org.http4s.server.blaze._
import org.http4s.server.Router
import org.http4s.server.middleware.CORS
import org.http4s._
import org.http4s.dsl.Http4sDsl
import zio._
import zio.clock._
import zio.console._
import zio.interop.catz._
trait HelloRepository
{
def getHello(name: String): ZIO[AppEnvironment, Nothing, String]
}
trait AppEnvironment extends Console with Clock
{
val helloRepository: HelloRepository
}
object Main extends App {
type AppTask[A] = RIO[AppEnvironment, A]
val dsl: Http4sDsl[AppTask] = Http4sDsl[AppTask]
import dsl._
val httpApp: HttpApp[AppTask] = Router[AppTask](
"/" -> HttpRoutes.of[AppTask] {
case GET -> Root / "hello" / name => Ok( ZIO.accessM[AppEnvironment](_.helloRepository.getHello(name)) )
}
).orNotFound
val program = for {
server <- ZIO.runtime[AppEnvironment]
.flatMap {
implicit rts =>
BlazeServerBuilder[AppTask]
.bindHttp(8080, "0.0.0.0")
.withHttpApp(CORS(httpApp))
.serve
.compile
.drain
}
} yield server
val runEnv = new AppEnvironment with Console.Live with Clock.Live
{
val helloRepository = new HelloRepository
{
def getHello(name: String): ZIO[AppEnvironment, Nothing, String] = ZIO.succeed(s"Hello $name")
}
}
def run(args: List[String]) =
program
.provide(runEnv)
.foldM(err => putStrLn(s"Execution failed with: $err") *> ZIO.succeed(1), _ => ZIO.succeed(0))
}
/tmp/http4s/build.sbt
val Http4sVersion = "0.20.0"
val CatsVersion = "2.0.0"
val ZioCatsVersion = "2.0.0.0-RC3"
val ZioVersion = "1.0.0-RC13"
val LogbackVersion = "1.2.3"
lazy val root = (project in file("."))
.settings(
organization := "example",
name := "example",
version := "0.0.1-SNAPSHOT",
scalaVersion := "2.12.8",
scalacOptions ++= Seq("-Ypartial-unification"),
libraryDependencies ++= Seq(
"org.typelevel" %% "cats-effect" % CatsVersion,
"dev.zio" %% "zio" % ZioVersion,
"dev.zio" %% "zio-interop-cats" % ZioCatsVersion,
"org.http4s" %% "http4s-blaze-server" % Http4sVersion,
"org.http4s" %% "http4s-dsl" % Http4sVersion,
"ch.qos.logback" % "logback-classic" % LogbackVersion,
),
addCompilerPlugin("org.spire-math" %% "kind-projector" % "0.9.6"),
addCompilerPlugin("com.olegpy" %% "better-monadic-for" % "0.2.4")
)
scalacOptions ++= Seq(
"-deprecation", // Emit warning and location for usages of deprecated APIs.
"-encoding", "UTF-8", // Specify character encoding used by source files.
"-language:higherKinds", // Allow higher-kinded types
"-language:postfixOps", // Allows operator syntax in postfix position (deprecated since Scala 2.10)
"-feature", // Emit warning and location for usages of features that should be imported explicitly.
"-Ypartial-unification", // Enable partial unification in type constructor inference
"-Xfatal-warnings", // Fail the compilation if there are any warnings
)
样本执行
bash-3.2$ cd /tmp/http4s
bash-3.2$ sbt
...
sbt:example> compile
...
[info] Done compiling.
[success] Total time: 5 s, completed Oct 24, 2019 11:20:53 PM
sbt:example> run
...
[info] Running Main
23:21:03.720 [zio-default-async-1-163838348] INFO org.http4s.blaze.channel.nio1.NIO1SocketServerGroup - Service bound to address /0:0:0:0:0:0:0:0:8080
23:21:03.725 [blaze-selector-0] DEBUG org.http4s.blaze.channel.nio1.SelectorLoop - Channel initialized.
23:21:03.732 [zio-default-async-1-163838348] INFO org.http4s.server.blaze.BlazeServerBuilder -
_ _ _ _ _
| |_| |_| |_ _ __| | | ___
| ' _| _| '_ _ _(_-<
|_||___|__| .__/ |_|/__/
|_|
23:21:03.796 [zio-default-async-1-163838348] INFO org.http4s.server.blaze.BlazeServerBuilder - http4s v0.20.0 on blaze v0.14.0 started at http://[0:0:0:0:0:0:0:0]:8080/
23:21:11.070 [blaze-selector-1] DEBUG org.http4s.blaze.channel.nio1.SelectorLoop - Channel initialized.
23:21:11.070 [blaze-selector-1] DEBUG org.http4s.blaze.channel.nio1.NIO1HeadStage - Starting up.
23:21:11.070 [blaze-selector-1] DEBUG org.http4s.blaze.channel.nio1.NIO1HeadStage - Stage NIO1HeadStage sending inbound command: Connected
23:21:11.070 [blaze-selector-1] DEBUG org.http4s.server.blaze.Http1ServerStage$$anon$1 - Starting HTTP pipeline
23:21:11.072 [blaze-selector-1] DEBUG org.http4s.blazecore.IdleTimeoutStage - Starting idle timeout stage with timeout of 30000 ms
此时打开后http://localhost:8080/hello/there我在浏览器中观察到了预期的输出。
希望这能有所帮助。