[rules-users] MVEL wows: what does "importInjectionRequired" mean?

[Wolfgang Laun]

The usual approach is to add all KPs in a single add call:

val session = createSessionUsingNoPackages

val kbuilder1 = KnowledgeBuilderFactory.newKnowledgeBuilder
kbuilder1.add("rule1.drl", ResourceType.DRL)
val kbuilder2 = KnowledgeBuilderFactory.newKnowledgeBuilder
kbuilder2.add("rule2.drl", ResourceType.DRL)
session addGlobal ("foo", foo)
session addGlobal ("Gar", gar)

session.knowledgeBase addKnowledgePackages (kbuilder2.getKnowledgePackages)

Perhaps this avoids the problem?
-W

On Wed, Dec 2, 2009 at 7:24 PM, Barry Kaplan <groups1 at memelet.com> wrote:
>
> I'm at my wits end. I have two simple rules in two separate packages, they
> are of the form:
>
> rule1:
>  import somepackage.*
>  global somepackage.Foo foo
>  ...
>  then
>     foo.doSomething(...)
>  end
>
> rule2:
>  import otherpackage.*
>  global otherpackage.Gar gar
>  ...
>  then
>     gar.doSomething(...)
>  end
>
> When mvel is resolving foo for rule1 it does so via
> org.mvel2.compiler.CompiledExpression#getValue:line-104
>
> When resolving gar for rule2 it does so via
> org.mvel2.compiler.CompiledExpression#getValue:line-107
>
> The difference is that for rule1 the variable 'importInjectionRequired' is
> true, which results in 'foo' being resolved, but for rule2 this variable is
> false which results in 'gar' not being resolved.
>
> I suspecting that its important that the packages and the global instances
> are added dynamically *after* the session is created (in scala'ish dialect):
>
> val session = createSessionUsingNoPackages
>
> val kbuilder1 = KnowledgeBuilderFactory.newKnowledgeBuilder
> kbuilder1.add("rule1.drl", ResourceType.DRL)
> session.knowledgeBase addKnowledgePackages (kbuilder1.getKnowledgePackages)
> session addGlobal ("foo", foo)
>
> val kbuilder2 = KnowledgeBuilderFactory.newKnowledgeBuilder
> kbuilder2.add("rule2.drl", ResourceType.DRL)
> session.knowledgeBase addKnowledgePackages (kbuilder2.getKnowledgePackages)
> session addGlobal ("Gar", gar)
>
> If just one or the other packages are added the session, then either
> variable is resolved. But if both are added the session the 'gar' is not
> resolved. It does not matter what order they added to the session. I can
> also try to access 'gar' in rule1 and it also will not be resolved.
>
> I guess I really don't expect any help on this, but I will boil it down to a
> simple test and submit it to jira
>
> -barry
> --
> View this message in context: http://n3.nabble.com/MVEL-wows-what-does-importInjectionRequired-mean-tp66496p66496.html
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