scala - 编译时依赖注入 play 项目中的 EvolutionsComponents

Question

我试图了解如何使用编译时 DI 运行进化。

import play.api.ApplicationLoader.Context
import play.api.cache.EhCacheComponents
import play.api.mvc.EssentialFilter
import play.api.routing.Router
import play.api._
import play.api.db.evolutions.{ DynamicEvolutions, EvolutionsComponents}
import play.filters.gzip.GzipFilter
import router.Routes

class AppLoader extends ApplicationLoader  {
  override def load(context: Context): Application = {
    LoggerConfigurator(context.environment.classLoader).foreach(_.configure(context.environment))
    new AppComponents(context).application
  }


}

class AppComponents(context: Context) extends BuiltInComponentsFromContext(context) with EhCacheComponents with EvolutionsComponents {

  lazy val applicationController = new controllers.Application(defaultCacheApi)
  lazy val usersController = new controllers.Users(defaultCacheApi)
  lazy val assets = new controllers.Assets(httpErrorHandler)

  applicationEvolutions

  // Routes is a generated class
  override def router: Router = new Routes(httpErrorHandler, applicationController, usersController, assets)

  val gzipFilter = new GzipFilter(shouldGzip =
    (request, response) => {
      val contentType = response.header.headers.get("Content-Type")
      contentType.exists(_.startsWith("text/html")) || request.path.endsWith("jsroutes.js")
    })

  override lazy val httpFilters: Seq[EssentialFilter] = Seq(gzipFilter)


}

但我不断收到错误错误：（19、7）类 AppComponents 需要是抽象的，因为类型 => play.api.db.DBApi 的 trait EvolutionsComponents 中的方法 dbApi 未定义 class AppComponents(context: Context) extends BuiltInComponentsFromContext(context ) 与 EhCacheComponents 与 EvolutionsComponents

我是 Scala 的新手。

Answer 1

dbApi来自DBComponentstrait，所以你的AppComponents类也需要扩展DBComponents. 您还需要扩展HikariCPComponents连接池。

class AppComponents(context: Context) extends BuiltInComponentsFromContext(context)
  with EhCacheComponents
  with EvolutionsComponents
  with DBComponents
  with HikariCPComponents {

请务必将evolutions和jdbc依赖项添加到您的build.sbt文件中。

Answer 2

我需要扩展所有这些。更多阅读 Cake Pattern Play 文档

class AppComponents(context: Context) extends BuiltInComponentsFromContext(context) with EhCacheComponents with EvolutionsComponents with DBComponents with HikariCPComponents{

并在 build.sbt 中添加 jdbc 支持

libraryDependencies ++= Seq(
 filters,
 evolutions,
 jdbc,
 cache,

……