[rules-users] required some input on String comparision in xml rulefile.

[Anstis, Michael (M.)]

You'll probably need to ensure the String object contains a valid object
reference and not a null.
 
If the database allows NULL values on a field then the String object
will be set to a null causing the problem you explain. An alternative is
to either set the String to an empty String ("") instead of null or
change your rule to first check whether the String is a null; for
example beanObject.getName() != null && beanObject.getName()=="smurf".


________________________________

	From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Mahantesh
	Sent: 29 January 2007 08:58
	To: rules-users at lists.jboss.org
	Subject: [rules-users] required some input on String comparision
in xml rulefile.
	
	
	Hi,
	
	I am using Drools 3 JBoss Rule Engine and xml file as a rule
file. when i am using integer condition in LHS part of rule file it is
working fine. 
	For example:  <eval> beanObject.getNumber >= 60 </eval> 
	
	but when using  string condition in LHS part of the rule file,
it is able to filter the data when setting and getting the data from the
dummy bean, but not able to filter the data when the data is coming from
the database its throwing the exceptions like this. 
	
	For Example: <eval> beanObject.getName()</eval>
	
	Exception like this.
	
	org.drools.RuntimeDroolsExcept 
	ion: java.lang.NullPointerException
	       at org.drools.rule.EvalCondition.isAllowed (Unknown
Source)
	       at
org.drools.reteoo.EvalConditionNode.assertTuple(Unknown Source)
	       at
org.drools.reteoo.TupleSource.propagateAssertTuple(Unknown Source)
	       at org.drools.reteoo.JoinNode.assertObject (Unknown
Source)
	       at
org.drools.reteoo.ObjectSource.propagateAssertObject(Unknown Source)
	       at org.drools.reteoo.ObjectTypeNode.assertObject(Unknown
Source)
	       at org.drools.reteoo.Rete.assertObject (Unknown Source)
	       at org.drools.reteoo.ReteooRuleBase.assertObject(Unknown
Source)
	       at
org.drools.reteoo.ReteooWorkingMemory.doAssertObject(Unknown Source)
	       at org.drools.common.AbstractWorkingMemory.assertObject
(Unknown Source)
	       at
org.drools.common.AbstractWorkingMemory.assertObject(Unknown Source)
	       at
org.drools.jsr94.rules.StatelessRuleSessionImpl.executeRules(Unknown
Source)
	       at
org.drools.jsr94.rules.StatelessRuleSessionImpl.executeRules (Unknown
Source)
	       at
rules1.TestRuleForXML.applyRuleTestingProcessVO(TestRuleForXML.java:176)
	       at
rules1.TestRuleForXML.applyForProcessVO(TestRuleForXML.java:55)
	size of the ouput list in  java file: 0 
	
	       at rules1.TestRuleForXML.main(TestRuleForXML.java:47)
	Caused by: java.lang.NullPointerException
	       at rules1.Rule_my_rule_0.eval0(Rule_my_rule_0.java:12)
	       at rules1.Rule_my_rule_0Eval0Invoker.evaluate
(Rule_my_rule_0Eval0Invoker.java:19)
	
	If you do a help regarding how to work with String condition in
LHS part, it will be great..
	
	Thanks in Advance,
	Mahantesh.
	






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