[wildfly-dev] JNDI and java:comp, slimming the server, and componentless naming contexts

[David M. Lloyd]

On 02/04/2014 09:55 AM, Eduardo Martins wrote:
> I’m ok with this, but a few comments inline:
>
> On 04 Feb 2014, at 13:39, David M. Lloyd <david.lloyd at redhat.com>
> wrote:
>
>> I think we need to look into a small redesign of how we handle
>> java:comp, java:module, and java:app.  The reasoning comes in
>> three parts:
>>
>> * Various specs require that certain names be bound globally
>> across all of java:comp.
 >>
>> * Various other specs implicitly expect to be able to query
>> theseglobally bound names even if there is no actual
>> component context.
>
> In theory this doesn’t make much sense to me, if that’s the idea in
> the specs then it would be preferable to additionally specify an
> entry in java:global too. For instance, there was recently a thread
> about a JPA PU pointing to a java:comp datasource, bound by a web
> component, and even if I don’t think that’s a good design the fact
> is the user idea was truly to have the web component point the way
> to the PU, but imagine that instead of a web component there was
> multiple EJBs binding different datasources to the same java:comp
> name, which one would the PU target?

Only the components which are globally bound would be visible if there
was no component context.  In cases like the one you mention, if a
component's binding is expected to be present, then the component
context must be active at that time.  If it cannot be active, then we
cannot support reading component-created bindings - end of story.  There
is not a third side to this coin. :-)

> Anyway I think the Java EE 7 RI has this feature implemented, so in
> the end users would benefit from common behaviour, just wished this
> was better specified.

Might as well wish that rain falls upwards.  The spec is the spec; we
need to support the behaviors that are specified.  No real room for
argument here either.

>> * Duplicating these bindings uses more resources than are
>> necessary.
>>
>
> I believe we still need the same individual MSC services due to at
> least resource injection of component scoped binds, after all, even
> if there are cases of truly global java:comp binds, there is always
> the feature where a component is allowed to override java:comp binds
> through XML and @Resource.

Possibly.  We can visit that issue if/when it comes up.

>> Therefore I think we need to make a small change - we should have a
>> "global" version of the three context-specific namespaces that act
>> as a sort of fallback if there's no (component|module|app)-specific
>> name bound at a location.  This allows us to do a few things:
>>
>> * Satisfy the spec issues * Reduce resource overhead * Allow
>> globally-configured things in the management config to bind to
>> component/module/app-specific namespaces
>>
>
> One could ask what’s wrong with java:global :-)

Nothing is wrong with java:global.  But do not get confused between
"what the user should do" and "what we are expected to support".  I'm
speaking strictly to the latter.  In that context, it doesn't help to
enter the former into the argument.

-- 
- DML