Scala – How to create a global variable with Play Framework 2.0

playframeworkplayframework-2.0scala

How do I create a global object/variable in Play Framework 2.0 using Scala?

I want to create a object that once instantiated, can persist between multiple controller actions so that different actions can still call on the same object (because initializing the object is very expensive).

Is this possible without storing it into the DB? I tried sticking the object into a the Global object for the onStart method as shown here:

http://www.playframework.org/documentation/2.0/ScalaGlobal

This was my code:

(in the root application folder)

object Global extends GlobalSettings {

  override def onStart(app:Application) {
    var foo = new Foo
    }
  }

}

And in my controller actions I try just calling the variable by name, but it didn't work.

Best Answer

If your globals also need to be available to the methods in Global, put them in Global.scala like so:

package object globals {
  lazy val abc = Play.maybeApplication.flatMap(_.configuration.getString("abc")).getOrElse("default_value_of_abc")
  lazy val someActor = Akka.system.actorOf(Props[SomeActor], name = "someActor")
}

And then use it in your controllers like this:

println(globals.abc)
globals.someActor ! SomeMessage

UPDATE

The documentation has since been updated how add Global.scala in an idiomatic Play! way, with docs for both Scala and Java.

Related Solutions

Scala – Play Framework – Redirect with params

Ellou'

A route is just a function, so you can pass arguments as usual:

// Redirect to /hello/Bob
def helloBob = Action {
    Redirect(routes.Application.hello("Bob"))    
}

This snippet comes from http://www.playframework.org/documentation/2.0/ScalaRouting (at the bottom)

Scala – How to integrate Play Framework 2.0 into Gradle build management using Maven dependencies

This is a very tricky business. SBT in Play is used for fetching dependencies, compiling source and templates, and for the SBT incremental compilation + auto-reloading feature. I have written a build.gradle script to resolve all Play 2.0 dependencies and set-up Eclipse or IntelliJ IDEA classpaths, and made it public here.

I will try to implement the compilation later when I have time, but that would require some research. Of course, you can add compile and run tasks that just delegate to SBT but that would require describing all your project dependencies in both SBT and Gradle, which will become difficult to manage.

Edit:

I have updated the sample build.gradle file. I have added playCompile and playClean tasks that should help in a CI environment. The playCompile task does the following:

Copy all user dependencies (defined in compile configuration) to lib/ folder. This works because Play will kindly pick up all jars from under lib/.
Execute play compile command to compile all sources, templates and other Play framework stuff.

You can use cleanCopyPlayLibs and playClean to remove the output of the above commands, respectively.

Note that there appears to be a strange problem (bug?) on Windows, which means that even if play compile fails, gradle will tell you it succeeded.

Reply to comment:

I think you are simply missing

repositories{
  mavenCentral()
}

in your file. Check this doc out.

Best Answer

Related Solutions

Scala – Play Framework – Redirect with params

Scala – How to integrate Play Framework 2.0 into Gradle build management using Maven dependencies

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