Dain has been working on a global jndi implementation that looks
really nice. However the deployment of bindings part of it has
brought up some long-festering architectural worries and perhaps we
are now in a position to deal with them in a systematic manner.
David Blevins pointed out to me a long time ago that one of the core
principles of openejb was that ejb containers should have nothing
transport specific attached to them. This was when I installed a
TSSBean reference in ejb containers to enable binding ejbs into
corba. I pointed out that letting the ejb container know jndi-names
and local-jndi-names had the same problem, and IIRC he agreed that
this was an architectural flaw. In any case, intentionally or not,
he convinced me that both the tssbean link and the jndi names should
not be attached to the ejb container. If you install dain's global
jndi stuff the jndi names now get recycled up to 3 times: for the
openejb proprietary jndi impl, global jndi, and corba. The global
jndi connector binding creates a similar but worse problem for j2ca
connectors, since it tries to bind using only the "name" component of
the abstract name, rather than allowing a specific global jndi name,
and AFAICT it doesn't let you specify which connectors you want to bind.
I think for all of these situations a cleaner runtime solution is a
component that links the thing you want to bind and the binding
context, and includes the name(s) you want to bind under. Currently
this would I think have to be a gbean. This is what Dain implemented
for gbean bindings. So, I'm proposing that bindings for connectors
in global jndi, and ejbs in global jndi, corba, and the openejb jndi,
each be set up by gbeans, each holding the name(s) to bind under and
a reference to the object to be bound. This part is pretty easy to
write.
Slightly harder is deployment: setting up these gbeans. If we modify
our schemas this can be done using NamingBuilders: here they won't be
constructing the components jndi context but rather exposing the
component in various naming systems. I think the really hard part is
figuring out some xml that is manageable to write and expresses the
meaning clearly.
For connectors it's pretty easy, we can just have a repeating element
<global-jndi-name>foo</global-jndi-name>
For ejbs with the current 3 naming systems it's a bit harder. One
possibility would look something like this:
<jndi>
<global/>
<corba>
<tss-link>foo-tss</tss-link>
</corba>
<openejb/>
<remote-name>foo</remote-name>
<local-name>bar</local-name>
</jndi>
where the global, corba, and openejb elements indicate which naming
system to bind to and the names are supplied with remote-name and
local-name. A remote jndi would ignore the local-name elements. You
could have multiple jndi elements to get different bindings in
different naming systems.
To make this extensible the naming system elements would have to be
in a substitution group and extend an abstract element. The ones we
know about now could all be in the same namespace.
Thoughts?
thanks
david jencks
