[cdi-dev] CDI-519 notes

Hi all, John is questioning the clarification introduced in CDI-519. I think it's correct although not quite intuitive. Below are some notes we should consider (I know it's long but the topic is quite complicated): CreationalContext ================= Besides other things, holds the references to all depenent bean instances together with their CCs (for normal scopes this is the responsibility of the context). So that these could be correctly destroyed when CC.release() is called. Note that the context must pass the same instance of CC to Contextual.destroy() that it passed to Contextual.create() when it created the instance. Possible "leak" description =========================== The problem is if an Instance is injected into a normal scoped bean Foo and is used to get other @Dependent bean instances via Instance.get(). Each of this call returns a new depenent bean instance bound to the lifecycle of the Instance, which is also depenent and so it's effectively bound to the lifecycle of Foo. And that was the original motivation to introduce Instance.destroy(). Instance.select() ================= The spec states the select() method returns a child Instance. What is that "child" is not defined though. In Weld, a child Instance shares the CreationalContext of the parent Instance. And I think this makes sense. CDI-519 summary =============== Instance.destroy() cannot be used for dependent bean instances not created by the same Instance object. The reason: a dependent bean instance does not know the object it depends on. So if we pass a dependent bean instance it must be "managed" by the CC of the Instance. Otherwise, we would not be able to destroy the bean instance and all its dependent dependencies correctly. From the spec point of view it's clear: "An instance of a bean with scope @Dependent obtained by direct invocation of an Instance is a dependent object of the instance of Instance." A dependent bean instance is bound to the lifecycle of Instance (or one of its child) so the Instance should be responsible for destroying it. Done. From the user point of view: I don't think it's a big problem. BTW it does not work in any CDI 1.1+ version of Weld. I'm not sure about OWB. Impl notes ========== If we allow this then we would probably have to create some central registry of CCs and during Instance.destroy() iterate over all these CCs and try to destroy given depenent bean instance. This will be complicated, error-prone and inefficient. Thanks, -- Martin Kouba Software Engineer Red Hat, Czech Republic