Play-Java + Futures/Promises.. where are we heading? [2.4+]

[Dominik Dorn]

I recently had a discussion on how to do asynchronous programming in a Play-Java project (2.4) 

in regards of where Play is heading (2.4 -> 2.5 -> 3.0).

Java 8 introduced CompletableFuture, yet Plays code base still is using play.libs.Promise. 

The question now is how to proceed, especially for writing own code. 

My current app will use a lot of WS-Requests against a backend system, so plays Promises are a natural fit for the webapp,
when the code stays in the project. 

However, we're also evaluating if we should create a API out of the created code, to allow reusing it in other Java projects.

One approach would be to use CompeletableFuture in the interfaces and map from Plays WSClients Promise -> CompletableFuture in the

Impl of the interface. However, when using this interface from a Play-Controller, we have to remap from a CompletableFuture to a Promise.

Another approach would be to adjust the Play-Framework to also allow Actions that return a CompletableFuture<Result> to be used in Controllers.

Any ideas/insights are greatly appreciated.

Cheers,

Dominik

[Christian Schmitt]

Currently Play 2.5 will definitly support CompletionStage which is the interface of CompletionFuture, there is also an Issue and a Merged PR about that:

https://github.com/playframework/playframework/issues/4691

It looks like 2.4 and 2.5 will compile if you used F.Promise and from there on you should remove as many F.Promise as possible.

[Niels Boldt]

Currently Play 2.5 will definitly support CompletionStage which is the interface of CompletionFuture, there is also an Issue and a Merged PR about that:

https://github.com/playframework/playframework/issues/4691

It looks like 2.4 and 2.5 will compile if you used F.Promise and from there on you should remove as many F.Promise as possible.

At https://docs.google.com/document/d/11sVi1-REAIDFVHvwBrfRt1uXkBzROHQYgmcZNGJtDnA/pub it says

"Replace play.libs.F.Promise with java.util.concurrent.CompletionStage in Java APIs"

Does it mean that only the java version will be affected. What does it mean with respect to Futures. Would it be possible in the scala version of 2.5 just to use java 8 futures as scala futures without a wrapper or would you still need to wrap them with something like https://github.com/scala/scala-java8-compat

Thanks

Niels 

Am Sonntag, 30. August 2015 23:29:53 UTC+2 schrieb Dominik Dorn:

I recently had a discussion on how to do asynchronous programming in a Play-Java project (2.4) 

in regards of where Play is heading (2.4 -> 2.5 -> 3.0).

Java 8 introduced CompletableFuture, yet Plays code base still is using play.libs.Promise. 

The question now is how to proceed, especially for writing own code. 

My current app will use a lot of WS-Requests against a backend system, so plays Promises are a natural fit for the webapp,
when the code stays in the project. 

However, we're also evaluating if we should create a API out of the created code, to allow reusing it in other Java projects.

One approach would be to use CompeletableFuture in the interfaces and map from Plays WSClients Promise -> CompletableFuture in the

Impl of the interface. However, when using this interface from a Play-Controller, we have to remap from a CompletableFuture to a Promise.

Another approach would be to adjust the Play-Framework to also allow Actions that return a CompletableFuture<Result> to be used in Controllers.

Any ideas/insights are greatly appreciated.

Cheers,

Dominik

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