[jboss-as7-dev] Overriding Deployment Descriptors

[Jason T. Greene]

On 4/5/12 3:52 AM, Chris Kriel wrote:
> Are you sure that this truly reflects what most users want? Are you not just
> adding a lot of complexity to cater for the whim of a small group of users?
>> From what I can gather from this thread, the motivation for these overrides
> are rather thin. It is based on some users having a "policy" to not
> break-open deployment artefacts. How overriding is better or safer that
> "breaking open" escapes me at the moment.
>
> Very much part of the EJB specification is the definition of roles and
> responsibilities. As you know, it describes a definite role for composing
> (and by implication "breaking-open" to recompose) artefacts. If your
> configuration is too dynamic for this approach then it is a matter of
> application design to pick this up from elsewhere (DB or properties file).

I certainly see where you are coming from. In fact I do agree that this 
feature could be used as a crutch over better ways to solve the problem.

There are, however, legitimate reasons / use-cases for an override. Here 
is a few in no particular order:

1. Third-party application - Some third party applications need 
customizations for either the environment (ip addresses, etc), or in 
some cases running on JBoss AS (the case app was primarily tailored to 
another app server). If you followed Stuarts proposal #2 of deploying 
the override first, then updating a newer thirdparty app is a bit 
simpler, you just deploy the new version, and the same overrides take effect

2. Staging / Dev / Prod deltas - A good example is @Alternative in CDI, 
you specify which set of beans you get in beans.xml Another example is 
that applications can now specify environmental values in annotations 
(e.g.in EE6 you can now specify @DataSourceDefinition with a URL and a 
user/pass). Having the ability to provide a per-environment DD lets you 
override those values. (Another thing we are looking at doing is 
supporting sys props in deployment descriptors as a vendor extension, 
which offers another way to skin this cat).

3. Geographic/Region deltas - Very similar to 2 You might want to add 
certain values like "distinct-name" (used by EJB remote invocation to 
differentiate connections)

-- 
Jason T. Greene
JBoss AS Lead / EAP Platform Architect
JBoss, a division of Red Hat