parameter injection

[asookazian]

from ref doc:

CDI also supports parameter injection for some other methods that are invoked by the container. For instance, parameter injection is supported for producer methods:

@Produces Checkout createCheckout(ShoppingCart cart) {
    return new Checkout(cart);
}

This is a case where the @Inject annotation is not required at the injection point.

Plz explain why/how this works.  Not sure how I'd know if injection is involved in this context or not by just looking at this method...

[swd847]

Where else is the parameter going to come from? The method is being invoked by the container, so the container could either pass in null (which is kind of useless) or inject the parameter.

[asookazian]

Ok, but can a client (e.g. session bean) call that method as well?  Sorry for the stupid questions...

Or are @Produces provider methods only called by the container?

[swd847]

Anything can call it, it is a POJO, in which case the parameter is not injected.

[asookazian]

where is the value injected from if the container calls the producer method?  From a scope or what?

[nickarls]

From the same place as if you would have a field

@Inject private ShoppingCart cart

That is, the context of the scope of the ShoppingCart