Play Ebean dependency for DI (play2.4.x)

[pycloux]

Hi,
I am facing an issue with my DI configuration.
I need to access the database in my singleton "at initialization".
What is the dependency which I should set to ensure that Ebean is activated "before" my singleton is injected by Guice ?
Regards,
PYC

[pycloux]

Here is an update.
I think I found a solution:

1. I "disabled" the Ebean-play default module.
   play.modules.disabled += "play.db.ebean.EbeanModule"
2. I added the binding for EbeanConfig in my own module (in order to manage by myself the Ebean dependencies)
3. I created a component which using a dependency on EbeanConfig and registers a default EbeanServer in its constructor. Then I ensure that the components using Ebean depends on this component.

Not sure that it is the best possible option but at this stage I have no better solution.

[justinnichols]

@pycloux would you mind posting an example of your workaround with code? I'm running into the same issue. Basically I have a timing problem where Ebean is not quite done at the time I need to use it with my module.

[jroper]

All you need to do is declare a dependency on play.db.ebean.EbeanConfig.

[justinnichols]

I determined that at some point yesterday by doing this in one of my @Singleton components:

@Inject
    public CustomComponentImpl(Configuration configuration, EbeanConfig ebeanConfig) {
        super(configuration, ebeanConfig);
   }

The problem is that even when doing this, the following code still produces a timing issue problem that results in the error Caused by: java.lang.RuntimeException: DataSource user is null? (and I have my config set up perfectly fine with a proper username/password and url and the reason I know this is that it works some times and doesn't other times):

this.datasource = configuration.getString("datasource.name");
this.db = Ebean.getServer(this.datasource);

[justinnichols]

So it turns out it's not enough to just wait for EbeanConfig. You also have to wait for DynamicEvolutions. This seemed to work without fail:

@Inject
public CustomComponentImpl(Configuration configuration, DynamicEvolutions dynamicEvolutions, EbeanConfig ebeanConfig) {
     super(configuration, ebeanConfig);
}

[pycloux]

Hi All,

Sorry for the late answer.
Actually I had to do a lot more because of the fact that Ebean startup and shutdown is happening independently from the dependency injection (and because we are not using the dynamic evolution features).

First I disabled the Ebean module in my configuration file:

play.modules.disabled += "play.db.ebean.EbeanModule"

Then I created an injectable component (which I register in my own module) which is requested by the modules which depends on the database.
This component depends on:

• ApplicationLifecycle lifecycle
• Environment environment
• Configuration configuration
• EbeanConfig ebeanConfig
• DBApi dbApi

The most important one (as stated by @jroper ) is the EbeanConfig.

Within this module, I am dealing myself with the EBean server start (and stop using the ApplicationLifecycle object):

    /**
     * Initialize the database
     */
    private void init(Configuration configuration) {
        // Register the Ebean server as the default one
        ServerConfig serverConfig = getEbeanConfig().serverConfigs().get(getEbeanServerDefaultName());
        Ebean.register(EbeanServerFactory.create(serverConfig), true);
    }

This solve the "startup" issue.
But you'll notice that by default, Ebean registers a "shutdown hook".
This means that it stops as soon as you ask the application to stop.
This was causing some issues in our application since the shutdown was happening completely independently of the injection order. So sometime Ebean was shutdown while some components needed it to be up.

For this last challenge, please see ebean-orm/ebean#427

If you want an example, you can see the code in our application https://github.com/theAgileFactory/app-framework/blob/master/app/framework/services/database/AbstractDatabaseDependencyServiceImpl.java.
This may not be easy to grasp since the class has many more feature but that's live and working.

Regards,

PYC

[justinnichols]

Thanks @pycloux ! I will see if I run into the same kinds of issues. Presently the only issue I have (which may be related to what you posted) is that the above CustomComponentImpl I suggested doesn't wait for evolutions to complete (even though it waits for the DynamicEvolutions component to be ready). Therefore, when my module starts, it isn't waiting for the evolutions to be completed (even with autoApply set to true) which will cause the module to fail starting (since an eagerly() bound component attempts to use Ebean and the database).