Using variables in Expressions

[vanyatka]

Hi,

I'd like to use a business context variable in the EL block, like this:

<decision name="my node" expression="#{filteredBannersCount}">...

This variable is declared in SLSB (via Seam) like this:

@Out(scope = ScopeType.BUSINESS_PROCESS, required = false)
 private String filteredBannersCount;

However, it seems EL should point to methods only and not variables.
I get the following error trying to use it:

13:28:46,887 FATAL [application] javax.ejb.EJBTransactionRolledbackException: Identity 'filteredBannersCount' does not reference a MethodExpression instance, returned type: java.lang.String
javax.faces.el.EvaluationException: javax.ejb.EJBTransactionRolledbackException: Identity 'filteredBannersCount' does not reference a MethodExpression instance, returned type: java.lang.String

Can we use business context vars in expressions?

Thanks,

[kukeltje]

No idea where this touches jBPM, and since you provide only a partial stacktrace it is hard to help out. Please provide more info

[vanyatka]

For the example's sake let's take this jPDL snippet from Seam dvd example

 <decision name="decide" expression="#{orderApproval.howLargeIsOrder}">
 <transition name="large order" to="approval"/>
 <transition name="small order" to="process"/>
 </decision>

Don't be confused, expression here is jBPM Expression Language, nothing to do with Seam EL (Or am I wrong?).

My question is, can I put a variable from business context in the expression?

[kukeltje]

process variables yes, fields from objects no (like in the last example). The Business Context is a seam thing. And I have no clue (yet, going to experiment with it later this month) how they relate to processvariables and the EL resolver. There are some issues with injecting and outjecting them and in the seam example (from what I've seen weeks/months ago) processvariables are only used when explicitly set via the jbpm context and not out-/injecting them. If injecting/outjecting them (seam job) works ok, using them in the EL should also work.

To make a long story short. The behaviour is not wel documented (if at all) and needs some more complex examples

[vanyatka]

Thanks, Ronald.
I'll try ask the same question on Seam forum.

[vanyatka]

I'm a bit put down seeing lack of information on using EL in jBPM.
The maximum I could find is a chapter Expressions http://docs.jboss.org/jbpm/v3/userguide/jpdl.html#expressions in the jbpm reference guide.

There is not a single mentioning of how to use them among jBPM examples.
Sure, there are pieces of code scattered through Internet and searchable by Google, but it feels sorta wrong learning stuff that way, it is inconsistent.

It would be nice to see more EL examples in the manual, I guess I might raise a feature request if I'm not alone on this. Especially this applies to using jBPM with Seam (as stated towards the end of the above mentioned chapter).

[kukeltje]

If you've used google, you probably found: http://www.google.nl/search?q=jbpm+el+examples&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

As mentioned before and you conclusion from the docs, the plain jBPM EL resolver is kind of minimalistic but to a large extend does it's job.

The resolver in jBPM is pluggable though, that is the way you get access to the Seam backend beans. More examples in this area would also be nice

[vanyatka]

BTW, it turns out that in case Seam is used with jBPM it is Seam (not jBPM) who deals with EL resolution.

http://seamframework.org/Community/UsingJBPMELInSeam