[rules-users] mythical functions

[Barry Kaplan]

Interesting, if I change from mvel to java and remove the package statement:

----
function String f() {
  return "function";
}

rule "Invoke function"
when
  eval(true)
then
  System.out.println("*** f=" + f());
end
---

Then this works.

So then, what permutations of mvel/java actually work:

--------------------------------------------------------------
1. Java + Qualified package:

----
package systeminsights.plugin.core.schedule

function String f() {
  return "function";
}

rule "Invoke function"
when
  eval(true)
then
  System.out.println("*** f=" + f());
end
---
 
Nope, this gives the obscure exception

org.drools.RuntimeDroolsException: java.lang.ClassNotFoundException:
systeminsights.plugin.core.schedule.Rule_Invoke_function_0ConsequenceInvoker


--------------------------------------------------------------
2. Java + simple package

----
package systeminsights
...
----

Yep, this works. 

--------------------------------------------------------------
3. Mvel + qualified package + strict

Nope:

[Error: Failed to compile: 1 compilation error(s): 
 - (1,3) unable to resolve method using strict-mode: java.lang.Object.f()]
[Near : {... Unknown ....}]
             ^
[Line: 1, Column: 0]

--------------------------------------------------------------
4. Mvel + qualified package + non-strict

Nope:

	at
org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:23)
	at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:975)
	at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:915)
	at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1121)
	at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:698)
	at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:664)
	at
org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:198)
	at
systeminsights.infra.drools.DroolsGroovyTestFixture.fireAllRules(DroolsGroovyTestFixture.groovy:89)
	at
systeminsights.infra.drools.DroolsGroovyTestFixture._clinit__closure19(DroolsGroovyTestFixture.groovy:226)
	at
systeminsights.infra.drools.DroolsGroovyTestFixture.getProperty(DroolsGroovyTestFixture.groovy)
	at systeminsights.plugin.core.schedule.FunctionsTest.With device(_) ->
device(_) is effective(FunctionsTest.groovy:19)
Caused by: [Error: unable to access property (null parent): f]
[Near : {... Unknown ....}]
             ^
[Line: 1, Column: 0]
	at
org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:860)

--------------------------------------------------------------
5. Mvel + simple package + strict

----
package systeminsights

dialect "mvel"

function String f() {
  return "function"
}

rule "Invoke function"
when
  eval(true)
then
  System.out.println("*** f=" + f())
end
---

Nope:

[Error: Failed to compile: 1 compilation error(s): 
 - (1,3) unable to resolve method using strict-mode: java.lang.Object.f()]
[Near : {... Unknown ....}]
             ^
[Line: 1, Column: 0]

--------------------------------------------------------------
6. Mvel + simple package + non-strict

Nope:

org.drools.runtime.rule.ConsequenceException: rule: Invoke function

	at
org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:23)
	at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:975)
	at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:915)
	at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1121)
	at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:698)
	at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:664)
	at
org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:198)
	at
systeminsights.infra.drools.DroolsGroovyTestFixture.fireAllRules(DroolsGroovyTestFixture.groovy:89)
	at
systeminsights.infra.drools.DroolsGroovyTestFixture._clinit__closure19(DroolsGroovyTestFixture.groovy:226)
	at
systeminsights.infra.drools.DroolsGroovyTestFixture.getProperty(DroolsGroovyTestFixture.groovy)
	at systeminsights.plugin.core.schedule.FunctionsTest.With device(_) ->
device(_) is effective(FunctionsTest.groovy:19)
Caused by: [Error: unable to access property (null parent): f]
[Near : {... Unknown ....}]
             ^
[Line: 1, Column: 0]
	at
org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:860)

--------------------------------------------------------------
7. Mvel + no package + strict

Nope:

[Error: Failed to compile: 1 compilation error(s): 
 - (1,3) unable to resolve method using strict-mode: java.lang.Object.f()]
[Near : {... Unknown ....}]
             ^
[Line: 1, Column: 0]
	at
org.mvel2.compiler.ExpressionCompiler.compile(ExpressionCompiler.java:78)

--------------------------------------------------------------
8. Mvel + no package + non-strict

Nope:

Same error as 6



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