Service validation

[dmlloyd]

Say I've got a service that has some dependencies that need to be injected before it can start up.

My first question is, when do the dependencies get injected, with relation to the service lifecycle methods? And secondly, how can I, within my service bean, validate that all the required dependencies are met? If there's a problem, can I e.g. throw an exception from my start() method to prevent the service from being started, or is there a "cleaner" way to validate dependencies?

Thanks, sorry if these are dumb questions but I can't seem to find anything in the user manual covering these topics.

[alesj]

Say I've got a service that has some dependencies that need to be injected before it can start up.
My first question is, when do the dependencies get injected, with relation to the service lifecycle methods?

It again depends where you want to inject. ;-)

Lifecycle order:

ControllerState.NOT_INSTALLED
ControllerState.PRE_INSTALL
ControllerState.DESCRIBED
ControllerState.INSTANTIATED
ControllerState.CONFIGURED
ControllerState.CREATE
ControllerState.START
ControllerState.INSTALLED

Constructor injection happens as Instantiated.
Property injection at Configured.
Create method invocation (+ parameter injections) at create. :-)
Start at ...

And I've just added that installs can be applied at any state:
- http://jira.jboss.com/jira/browse/JBMICROCONT-242

And secondly, how can I, within my service bean, validate that all the required dependencies are met?

You don't need to.
If you define your dependencies right (and it's a very pluggable system aka defining you own dependencies is trivial), MC is gonna take care that they are all met, or the service won't move fwd.

If there's a problem, can I e.g. throw an exception from my start() method to prevent the service from being started, or is there a "cleaner" way to validate dependencies?

If whatever exception is thrown during any state of bean/service lifecycle, the MC is gonna put this context into error state.
See this discussion for more details:
- http://www.jboss.org/index.html?module=bb&op=viewtopic&t=130374&start=0
But you can manually move service in MC.
And perhaps if the validation at that point is negative you move your service a (few) step(s) back. And proceed when you expect all is OK.
It's again all about what is valid for you.

[dmlloyd]

OK, then I think I'm confused - how does the controller state lifecycle relate to the service lifecycle? The service lifecycle seems to define four trasitions - create, start, stop, and destory. But the controller can be in 8 different states.

[alesj]

OK, then I think I'm confused - how does the controller state lifecycle relate to the service lifecycle? The service lifecycle seems to define four trasitions - create, start, stop, and destory. But the controller can be in 8 different states.

We have more fine grained states than the usual lifecycles. ;-)
And what you call stop and destroy are respectively start and create on the way 'back', at uninstall.

What are usually the states where the services get instantiated and configured?

[dmlloyd]

"alesj" wrote:
We have more fine grained states than the usual lifecycles. ;-)
And what you call stop and destroy are respectively start and create on the way 'back', at uninstall.

Yeah, I figured out that much. So the lifecycle methods described in http://tinyurl.com/2qlxsq (13.3 of the user manual) represent transitions between three states in each direction. Which of the 8 controller states does each of the three states correspond to? Or are they completely independent and unrelated (and thus am I just confusing myself)?

[alesj]

Which three states you have in mind?

I'll do a simple explanation of what each state does, or better, what each action corresponding to state does:

In install phase:
NOT_INSTALLED - initial state
PRE_INSTALL - initialize scoped metadata, check for hierarchy of Controllers
DESCRIBED - add aop dependencies, handle IoC annotations
INSTANTIATED - instantiate pojo
CONFIGURED - configure pojo's propertys with values
CREATE - invoke create method (if exists)
START - invoke start method (if exists)
INSTALLED - register bean into registry, apply supplies

In uninstall phase:
INSTALLED - unregister bean from registry, clear supplies
START - invoke stop method (if exists)
CREATE - invoke destroy method (if exists)
CONFIGURED - nullify pojo's propertys
INSTANTIATED - nullify target pojo
DESCRIBED - clear IoC annotations
PRE_INSTALL - clear any Controller hierarchy (if applied) and scoped metadata
NOT_INSTALLED - end state

And actually there are more than 8 Controller states, to confuse you even more. :-)
But the one's mentioned are relevant for the POJOs. ;-)

[dmlloyd]

Ah - I get it! I was confused after all. And in fact, re-reading the lifecycle chapter, you do explain this a bit.

OK, this totally makes sense now. Sorry for the dumb questions.