Play 2.7.x：ProvisionException：无法提供具有循环依赖项的play.api.Application

Question

从Play 2.7.x起，我无法获得play.api.Application，我尝试了多种方法，例如从自定义模块（插件）甚至从我的ApplicationController。我总是收到以下循环依赖错误：

ProvisionException: Unable to provision, see the following errors:

1) Found a circular dependency involving play.api.Application, and circular dependencies are disabled.
  at play.api.DefaultApplication.class(Application.scala:252)
  while locating play.api.DefaultApplication
  while locating play.api.Application
    for the 10th parameter of controllers.ApplicationController.<init>(ApplicationController.scala:30)
  while locating controllers.ApplicationController
    for the 2nd parameter of router.Routes.<init>(Routes.scala:111)
  while locating router.Routes
  while locating play.api.inject.RoutesProvider
  while locating play.api.routing.Router
    for the 3rd parameter of play.api.http.DefaultHttpRequestHandler.<init>(HttpRequestHandler.scala:120)
  while locating play.api.http.DefaultHttpRequestHandler
  while locating play.api.http.HttpRequestHandler
    for the 6th parameter of play.api.DefaultApplication.<init>(Application.scala:253)
  at play.api.DefaultApplication.class(Application.scala:252)
  while locating play.api.DefaultApplication
  while locating play.api.Application

1 error

例如，从我的自定义模块DynamicTemplateLoader：

@Singleton
class DynamicTemplateLoader @Inject(app: play.api.Application) {
   ...
}

或来自我的ApplicationController：

class ApplicationController @Inject() (
  components: ControllerComponents
)(
  implicit app: play.api.Application
) extends AbstractController(components) with I18nSupport {
   ...
}

为什么我需要play.api.Application？我需要掌握app.classloader才能使用插件的反射。

Answer 1

通过从注入play.api.Application实例改为注入javax.inject.Provider[play.api.Application]实例解决了该问题。