[rules-users] Modify a global variable with mvel dialect

[Joshua Jackson]

Dear all,

How do we modify a global variable with mvel dialect inside rules file
without getting
java.lang.UnsupportedOperationException: External Variable
identifer='allowance' type='class java.lang.Double' is final, it
cannot be set
 [testng] 	at org.drools.base.mvel.DroolsMVELGlobalVariable.setValue(DroolsMVELGlobalVariable.java:37)
   [testng] 	at
org.drools.base.mvel.DroolsMVELFactory.createVariable(DroolsMVELFactory.java:199)
   [testng] 	at
org.mvel.ast.AssignmentNode.getReducedValueAccelerated(AssignmentNode.java:80)
   [testng] 	at org.mvel.MVELRuntime.execute(MVELRuntime.java:88)
   [testng] 	at
org.mvel.CompiledExpression.getValue(CompiledExpression.java:108)
   [testng] 	at org.mvel.MVEL.executeExpression(MVEL.java:230)
   [testng] 	at
org.drools.base.mvel.MVELConsequence.evaluate(MVELConsequence.java:47)
   [testng] 	at
org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:550)
   [testng] 	at
org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:514)
   [testng] 	at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:462)
   [testng] 	at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:424)

This is how I did it:
Java file:
public void run(){
		Double allowance = new Double(0);
		workingMemory.setGlobal("allowance", allowance);
				
		workingMemory.fireAllRules();
	}


Rules:
global Double allowance

dialect "mvel"

rule "Has Wife"
	no-loop	
	salience 20
	when
		e: Employee()
		income:Income()
		eval( e.isWife() )
	then
		System.out.println("Has Wife");
		allowance = allowance + 5000;
end

This works if I use java as the dialect.

Have I missed something?

Thanks in advance,
-- 
It's not going to be like this forever

Blog: http://joshuajava.wordpress.com/