[jboss-jira] [JBoss JIRA] Created: (JBRULES-515) java NullPointerException when using constraints between fields in same object

[Sridhar Chandrasekharan (JIRA)]

java NullPointerException when using constraints between fields in same object
------------------------------------------------------------------------------

                 Key: JBRULES-515
                 URL: http://jira.jboss.com/jira/browse/JBRULES-515
             Project: JBoss Rules
          Issue Type: Bug
      Security Level: Public (Everyone can see)
    Affects Versions: 3.0.4
         Environment: Linux
            Reporter: Sridhar Chandrasekharan
         Assigned To: Mark Proctor


Consider the following files:-
1) Foo.java
package com.foo;

public class Foo {
	private int a;
	private int b;
	public Foo(int a, int b) {
		super();
		this.a = a;
		this.b = b;
	}
	public boolean test()
	{
		return (a > b);
	}
	public int getA() {
		return a;
	}
	public int getB() {
		return b;
	}
	
}
******************************************************************************
2) FooTest.java
package com.foo;
import java.io.InputStreamReader;
import java.io.*;

 
import org.drools.RuleBase;
import org.drools.RuleBaseFactory;
import org.drools.WorkingMemory;
import org.drools.compiler.PackageBuilder;
import org.drools.rule.Package;

public class FooTest {
	
	
	/**
	 * This is a sample file to launch a rule package from a rule source file.
	 */
	    public static final void main(String[] args) {
	        try {
	        	
	        	//load up the rulebase
	            RuleBase ruleBase = readRule();
	            WorkingMemory workingMemory = ruleBase.newWorkingMemory();
	            
	            //go !
	            
	            workingMemory.fireAllRules();   
	            
	            
	        } catch (Throwable t) {
	            t.printStackTrace();
	        }
	    }

	    /**
	     * Please note that this is the "low level" rule assembly API.
	     */
		private static RuleBase readRule() throws Exception {
			//read in the source
			Reader source = new InputStreamReader( FooTest.class.getResourceAsStream( "/Foo.drl" ) );
			
			//optionally read in the DSL (if you are using it).
			//Reader dsl = new InputStreamReader( DroolsTest.class.getResourceAsStream( "/mylang.dsl" ) );

			//Use package builder to build up a rule package.
			//An alternative lower level class called "DrlParser" can also be used...
			
			PackageBuilder builder = new PackageBuilder();

			//this wil parse and compile in one step
			//NOTE: There are 2 methods here, the one argument one is for normal DRL.
			builder.addPackageFromDrl( source );

			//Use the following instead of above if you are using a DSL:
			//builder.addPackageFromDrl( source, dsl );
			
			//get the compiled package (which is serializable)
			Package pkg = builder.getPackage();
			
			//add the package to a rulebase (deploy the rule package).
			RuleBase ruleBase = RuleBaseFactory.newRuleBase();
			ruleBase.addPackage( pkg );
			return ruleBase;
		}
	
	}
***************************************************
3) Foo.drl
package com.foo


rule "Initialization rule"
	when
		#conditions
	then 
		assert(new Foo(1,1));
		assert(new Foo(2,1));
		assert(new Foo(2,3));
		assert(new Foo(3,2));
		assert(new Foo(3,4));
		assert(new Foo(4,3));
end

rule "a greater than b"
	when
		f : Foo(x : a, b < x)
		then 
		System.out.println("a=" + f.getA() + " b=" +  f.getB() );
end
******************************************
I get the following error when running the program

java.lang.NullPointerException
at org.drools.rule.BoundVariableConstraint.isAllowed(Unknown Source)
	at org.drools.common.BetaNodeBinder.isAllowed(Unknown Source)
	at org.drools.reteoo.LeftInputAdapterNode.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.base.DefaultKnowledgeHelper.assertObject(Unknown Source)
	at org.drools.base.DefaultKnowledgeHelper.assertObject(Unknown Source)
	at com.foo.Rule_Initialization_rule_0.consequence(Rule_Initialization_rule_0.java:7)
	at com.foo.Rule_Initialization_rule_0ConsequenceInvoker.evaluate(Rule_Initialization_rule_0ConsequenceInvoker.java:18)
	at org.drools.common.DefaultAgenda.fireActivation(Unknown Source)
	at org.drools.common.DefaultAgenda.fireNextItem(Unknown Source)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown Source)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown Source)
	at com.foo.FooTest.main(FooTest.java:27)
org.drools.spi.ConsequenceException: java.lang.NullPointerException
	at org.drools.common.DefaultAgenda.fireActivation(Unknown Source)
	at org.drools.common.DefaultAgenda.fireNextItem(Unknown Source)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown Source)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown Source)
	at com.foo.FooTest.main(FooTest.java:27)
Caused by: java.lang.NullPointerException
	at org.drools.rule.BoundVariableConstraint.isAllowed(Unknown Source)
	at org.drools.common.BetaNodeBinder.isAllowed(Unknown Source)
	at org.drools.reteoo.LeftInputAdapterNode.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.base.DefaultKnowledgeHelper.assertObject(Unknown Source)
	at org.drools.base.DefaultKnowledgeHelper.assertObject(Unknown Source)
	at com.foo.Rule_Initialization_rule_0.consequence(Rule_Initialization_rule_0.java:7)
	at com.foo.Rule_Initialization_rule_0ConsequenceInvoker.evaluate(Rule_Initialization_rule_0ConsequenceInvoker.java:18)
	... 5 more

If I change the 2nd rule to
rule "a greater than b"
	when
		f : Foo()
                and eval(f.test())
		then 
		System.out.println("a=" + f.getA() + " b=" +  f.getB() );
end

It works as expected.

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