Start the application

An application which is instantiated and has proper singletons can now be started.

The components which can be “started” need to implement the Start interface and define a start method:

import org.zalando.grafter.{Start, StartResult}
import cats.Eval

case class DoobieDatabase(config: DatabaseConfig) extends Start {
  def start: Eval[StartResult] =
    StartResult.eval("starting the database") {
      println("start the database here")
    }
}

Then starting the whole application is just a matter of calling startAll:

import org.zalando.grafter.syntax.rewriter._

val start: Eval[List[StartResult]] =
  application.startAll

val results = start.value

if (results.forall(_.success))
  println("ok")
else
  println("Something went wrong "+results.mkString("\n"))

startAll is going to recursively, bottom up, call all the components with a Start interface and collect the StartResults.

Stop the application

The application can also be stopped in the same manner. stopAll will stop each component implementing Stop from the top down.

The major difference between the startAll and stopAll is that all the components will try to be stopped regardless of failures.

Total for specification Start the application
Finished in	14 ms
Results	0 example, 0 failure, 0 error