Play allows first call to controller before DI is complete

nemoo · January 3, 2022, 2:25pm

When I use Playframework (2.8.11, scala) in dev mode via sbt ~run, it allows calls to controllers even though dependency injection via Guice has not been completed.

This is a problem for me, because I generate test data at play startup. This test data should be available before the first request hits the controller. My problem is that the request hits the controller before the test data has been created. I then have to hit F5 in the browser. This triggers a reload of the play application. Only then the test data bootstrapping is executed before the request is processed.

This slows down my development cycle considerably.

This is how I set up the test data (created this testdata branch for discussion):

github.com

nemoo/play-slick-synchronous-example/blob/testdata/app/modules/ApplicationModule.scala#L12

    
      
          
          
import com.google.inject.AbstractModule
          import net.codingwell.scalaguice.ScalaModule
          import play.api.{Configuration, Environment, Mode}
          import utils._
          
          

          
class ApplicationModule( environment: Environment,
                                   configuration: Configuration) extends AbstractModule with ScalaModule{
            override def configure(): Unit = {
              bind[DbBootstrap].self.asEagerSingleton()
              
              if (environment.mode == Mode.Prod)
                bind[WeatherService].to[WeatherServiceImpl]
              else
                bind[WeatherService].to[WeatherServiceMock]
          
          
  }
          }

github.com

nemoo/play-slick-synchronous-example/blob/testdata/app/modules/DbBootstrap.scala

package modules

import models.{ProjectRepo, TaskRepo, TestData}
import play.api.db.slick.DatabaseConfigProvider
import slick.jdbc.JdbcProfile
import play.api.Logger
import com.github.takezoe.slick.blocking.BlockingH2Driver.blockingApi._
import play.api.Environment
import play.api.Mode.Dev

import javax.inject.{Inject, Singleton}
import play.api.db.evolutions.ApplicationEvolutions
import scala.concurrent.Future
import scala.concurrent.ExecutionContext

@Singleton
class DbBootstrap @Inject() (
    testData: TestData,
    env: Environment,
    dbConfigProvider: DatabaseConfigProvider,

This file has been truncated. show original

This is the controller that should already consume the test data and fails if it is not there:

github.com

nemoo/play-slick-synchronous-example/blob/testdata/app/controllers/Application.scala#L62

    
      
              }
          }
          
          
def createProject(name: String): Action[AnyContent] = silhouette.SecuredAction { implicit request: SecuredRequest[AuthEnv, AnyContent] =>
            db.withSession { implicit session =>
              val id = projectRepo.create(name)
              Ok(s"project $id created")
            }
          }
          
          
def listProjects: Action[AnyContent] = Action { implicit request: Request[AnyContent] =>
            db.withSession { implicit session =>
              implicit val user: User = User("dummy", NormalUser)
          
          
    val temperature = weather.forecast("NYC")
              val projects = projectRepo.all
              if (projects.isEmpty) throw new RuntimeException("Test data is not available, aborting.")
              Ok(views.html.projects(projects, temperature, config))
            }
          }

Any ideas why Play processes the first request even though DI (and therefore test data creation via the DbBootstrap class) is not complete?

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Play allows first call to controller before DI is complete

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