Play! framework uses a of statics

Question

Waaah, the Play! framework has so many static methods. Where I go to school, we were told never ever to use any statics, yet Play! uses it like there's no tomorrow. Is that somehow okay? If so, why?

We (7 people and I) are planning to use the Play! framework for a project involving a web app. We decided to do it with Play! because it looks quite fun to do, all of us already know Java and the assignment is pretty hard so we wanted to focus on the actual assignment rather than also learning how to program in a different language.

We were always told, however, NEVER EVER to use 'static's in any Java program we developed, but when I look at Play! ... Well... about half the methods are static. </exaggeration>

I suppose, at the very least, we could use singleton objects (by using Scala, for example ^^) in order to program our project, but I'm quite concerned at how many statics there actually are in framework itself.

So, should I be concerned about this? Did the way the Play! developers programmed it make it so that all these statics don't pose a problem?

(For example, this thread has a rant about why static members should be avoided at all costs.)

Answer 1

Play takes a functional approach, like node.js for example, and arguably makes 'more sense' in Scala than in Java, as the Typesafe Stack is pushing, for example. As other posters have pointed out, Java is being augmented using bytecode instrumentation (a la Aspect J) to behave in a more stateless/functional way; Scala does this by default.

Answer 2

If you are an Object Orientated Programming purist, you shouldn't use static methods/fields, however they can be used safely, and don't have to be a cause for concern IMHO.

Answer 3

You can now use Spring DI within Play, see https://stackoverflow.com/a/16552598/10433. I'm using it and it works fine so far.

Answer 4

EDIT Now in Play 2.4, the injection is done automatically. So just adding @ at the beginning of the controller path in the file routes will make the trick:

GET     /                  @controllers.Application.index()

For older versions (2.1 to 2.3) you will have to override getControllerInstance in the Global class, like explained in the Documentantion.

Answer 5

One of the reasons to use static methods are the static imports which allow you to shorten the notation and make the code more readable. This is specially true when using utility libraries like Guava or Apache Commons in which you might have a lot of static calls.

Non-static controller methods are now supported in Play 2.1 via using controller injection, so it's not very clear why they were not there from start.

Answer 6

I suppose, at the very least, we could use singleton objects

Singleton in Java does not makes much difference than using all static. There is not much to store as state as well. I think you should not worry about it.

So, should I be concerned about this? Did the way the Play! developers programmed it make it so that all these statics don't pose a problem?

It would not. In fact, it's alright.