在 playframework 中像这样设置 GLOBAL 变量是一种好习惯吗？

Question

我在同事写的app/Global.scala里看到了这样的代码

import java.lang.reflect.Constructor
import securesocial.core.RuntimeEnvironment
import securesocial.core.providers._
import securesocial.core.providers.utils.Mailer
import services.UserService

import scala.collection.immutable.ListMap

object Global extends play.api.GlobalSettings {

  /**
   * The runtime environment for this app.
   */
  object MyRuntimeEnvironment extends RuntimeEnvironment.Default[User] {
    // override lazy val routes = new CustomRoutesService()
    override lazy val userService: UserService = new UserService()
    lazy val MailTemplates: MailTemplates = new MailTemplates(this)
    override lazy val mailer: Mailer = new Mailer(MailTemplates)
    // override lazy val eventListeners = List(new MyEventListener())
    override lazy val providers = ListMap(
      // oauth 2 client providers
      include(new FacebookProvider(routes, cacheService, oauth2ClientFor(FacebookProvider.Facebook))),
      // username password
      include(new UsernamePasswordProvider(userService, avatarService, passwordHashers))
    )
  }

  /**
   * An implementation that checks if the controller expects a RuntimeEnvironment and
   * passes the instance to it if required.
   *
   * This can be replaced by any DI framework to inject it differently.
   *
   * @param controllerClass
   * @tparam A
   * @return
   */
  override def getControllerInstance[A](controllerClass: Class[A]): A = {
    val instance = controllerClass.getConstructors.find { c =>
      val params = c.getParameterTypes
      params.length == 1 && params(0) == classOf[RuntimeEnvironment[User]]
    }.map {
      _.asInstanceOf[Constructor[A]].newInstance(MyRuntimeEnvironment)
    }
    instance.getOrElse(super.getControllerInstance(controllerClass))
  }
}

有没有人认为在 playframework 中将服务设置为全局值合适？

Answer 1

服务通常作为无状态单例实现，所以我认为这没问题。您的问题与一般依赖注入原则相关，而不是与 Play 相关。

Answer 2

是的。这是在没有使用依赖注入框架的情况下播放的标准依赖注入模式。它允许您请求范围变量类似于 Spring 请求范围。

您的实施看起来像是基于正在运行的 SecureSocial 示例实施。看 https://github.com/jaliss/securesocial/blob/master/samples/scala/demo/app/Global.scala

在 playframework 中像这样设置 GLOBAL 变量是一种好习惯吗？

Is it a good practice to set GLOBAL variables like this in playframework?

dependency-injection

scala

playframework-2.0

typesafe-activator