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<div dir="ltr"><font color="#000000" size="2" face="Tahoma">SUMMARY:</font></div>
<div dir="ltr"><font size="2" face="tahoma">I am getting a NPE when using modify() with a JavaBean that implements PropertyChangeSupport.
</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">I have included the original source and a proposed fix. Stack trace is also included.</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">This applies to Drools 5.0.1, and has been verified to also be a problem for 5.1.0.M1.</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">DETAIL:</font></div>
<div dir="ltr"><font color="#000000" size="2" face="Tahoma"></font> </div>
<div dir="ltr"><font color="#000000" size="2" face="Tahoma">I have a rule that looks like this:</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><b><font color="#960000" size="2"><font color="#960000" size="2">
<p align="left">rule</b></font></font><font size="2"> </font><font color="#008000" size="2"><font color="#008000" size="2">"Constrain to owner or published to public"</p>
</font></font><font size="2">
<p align="left"></font><b><font color="#960000" size="2"><font color="#960000" size="2">when</p>
</b></font></font><font size="2">
<p align="left"> $fact : ListFact(</p>
<p align="left"> path </font><b><font color="#960000" size="2"><font color="#960000" size="2">not</b></font></font><font size="2">
</font><b><font color="#960000" size="2"><font color="#960000" size="2">matches</b></font></font><font size="2">
</font><font color="#008000" size="2"><font color="#008000" size="2">".*owner.*"</font></font><font size="2">,</p>
<p align="left"> noopResponse == </font><b><font color="#960000" size="2"><font color="#960000" size="2">true</p>
</b></font></font><font size="2">
<p align="left">)</p>
<p align="left"></font><b><font color="#960000" size="2"><font color="#960000" size="2">then</b></font></font><font size="2">
</font></p>
<p align="left"></p>
<p align="left"><font color="#808000" size="2"><font color="#808000" size="2"></p>
</font></font><font size="2"></font><b><font color="#960000" size="2"><font color="#960000" size="2"> modify</b></font></font><font size="2">($fact)
<p></p>
<p align="left"> {</p>
<p align="left"> setPath( </font><font color="#008000" size="2"><font color="#008000" size="2">"[owner/username='' or publishlist/publish='All Users']"</font></font><font size="2">)</p>
<p align="left"> }</p>
<p align="left"></p>
<p align="left"></p>
</font><b><font color="#960000" size="2"><font color="#960000" size="2">
<p align="left">end</p>
</b></font></font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">The $fact is a JavaBean that implements PropertyChangeSupport, and I've verified that everything is working correctly at the bean level. When I run this rule, I get this exception:</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="1" face="Courier New">Caused by: java.lang.NullPointerException:<br>
at org.drools.common.EqualityKey.removeFactHandle(EqualityKey.java:109)<br>
at org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1435)<br>
at org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1350)<br>
at org.drools.common.AbstractWorkingMemory.propertyChange(AbstractWorkingMemory.java:1577)<br>
at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339)<br>
at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:276)<br>
at com.infotrustgroup.rules.RestFact.setPath(RestFact.java:264)<br>
at com.infotrustgroup.facts.ParametersFact.setPath(ParametersFact.java:105)<br>
at com.infotrustgroup.facts.ParametersFact.setPath(ParametersFact.java:74)<br>
at com.infotrustgroup.what.Rule_Constrain_to_owner_or_published_to_public_0.consequence(Rule_Constrain_to_owner_or_published_to_public_0.java:12)<br>
at com.infotrustgroup.what.Rule_Constrain_to_owner_or_published_to_public_0ConsequenceInvoker.evaluate(Rule_Constrain_to_owner_or_published_to_public_0ConsequenceInvoker.java:23)<br>
at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:934)<br>
... 38 more</font></div>
<div dir="ltr"><font size="1" face="Courier New"></font> </div>
<div dir="ltr"><font size="2" face="Tahoma">The offending line is marked below. It looks like maybe "this.instances" is null in the "else" clause.</font></div>
<div dir="ltr"><font size="2" face="Tahoma"></font> </div>
<div dir="ltr"><font size="1" face="courier new"> public void removeFactHandle(final InternalFactHandle handle) {<br>
if ( this.handle == handle ) {<br>
if ( this.instances == null ) {<br>
this.handle = null;<br>
} else {<br>
this.handle = (InternalFactHandle) this.instances.remove( 0 );<br>
if ( this.instances.isEmpty() ) {<br>
this.instances = null;<br>
}<br>
}<br>
} else {<br>
***<strong><em>this.instances.remove( handle );***<br>
</em></strong> if ( this.instances.isEmpty() ) {<br>
this.instances = null;<br>
}<br>
}<br>
}</font></div>
<div dir="ltr"><font size="1" face="courier new"></font> </div>
<div dir="ltr"><font size="2" face="Tahoma">It looks like someone else ran into this problem before, but only fixed it for the "if" portion, not the "else" portion. I modified the code as follows, and this seems to fix the NPE. Basically, I followed the pattern
from the "if" portion.</font></div>
<div dir="ltr"><font size="2" face="Tahoma"></font> </div>
<div dir="ltr"><font size="1" face="Courier New"> public void removeFactHandle(final InternalFactHandle handle) {<br>
if ( this.handle == handle ) {<br>
if ( this.instances == null ) {<br>
this.handle = null;<br>
} else {<br>
this.handle = (InternalFactHandle) this.instances.remove( 0 );<br>
if ( this.instances.isEmpty() ) {<br>
this.instances = null;<br>
}<br>
}<br>
} else {<br>
if(this.instances == null)<br>
{<br>
this.handle = null;<br>
}<br>
else<br>
{<br>
this.instances.remove( handle );<br>
if ( this.instances.isEmpty() ) {<br>
this.instances = null;<br>
}<br>
}<br>
}<br>
}<br>
</font></div>
<div dir="ltr"><font size="2" face="Tahoma">Please read around the formatting. Can someone verify if this is a correct fix, and if it should be applied to the codebase? It seems to work for me. It does not break any unit tests in drools-core 5.0.1 either.</font></div>
<div dir="ltr"><font size="2" face="Tahoma"></font> </div>
<div><font size="2" face="Tahoma">
<p style="MARGIN: 0in 0in 0pt" class="MsoNormal"><b><span style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt">Jason Smith<br>
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