EntityManager in Repositories

[ppllaxxa]

Hello,

We started our project with PlayFramework 2.6. This version allows us to use jpaApi.em() in our code after invoking jpaApi.withTransaction.
It allows us to use this approche in most of the places. E.g.:
there is some complex logic where most of steps depends on DB connection:

public CompletionStage<Void> doSomeStuff() {
  return CompletableFuture.runAsync(() -> jpaApi.withTransaction(doSomeDbWork), executor);
}

and inside this doSomeDbWork there could be a lot of calls to other repositories(there could be chained calls) which need DB connection and we used there jpaApi.em() to perform DB calls.

But with PlayFramework 2.8 this possibility was removed and now we need to pass EntityManager as a parameter to each repository method to have a possibility take data from DB. And it is a pain.

I am asking an advise maybe I missed something in examples/migration guides and there is some other way to switch to 2.8 version without rewriting most of the project?

[mkurz]

Not sure if this is easily possible, but you could mimic what Play 2.8 did and set up your own ThreadLocal to store the EntityManager. You could take a look into the 2.8.x source code how Http.Context was set up.

Another possible solution would be that you switch most of your code to dependency injection, so that you inject the repositories into your controllers and into the repository you inject the jpaApi.

Also, do you need to use the same transaction for the duration of the whole request?
If so you could implement your own ActionCreator and inside that, before you call the delegate action, start the transaction, then pass the em you use via request attributes down to the next action and again in the action creator, when the request is finished, close the transaction.

If you need more help let me know.

[ppllaxxa]

Thank you for your advise. Do you know what was the reason to step away from approach in 2,7 with EntityManager in ThreadLocal store?

[mkurz]

@ppllaxxa You can read through https://www.playframework.com/documentation/3.0.x/JavaHttpContextMigration27

[ppllaxxa]

Thank you very mach!