[rules-dev] Drools on android -reply

[Wolfgang Laun]

On 2 January 2012 14:30, Matthew Versaggi <profversaggi at gmail.com> wrote:

> Here's what I got working and when it failed .... it was just the basic
> 'hello world' kind of stuff:
>
> Worked:
> final KnowledgeBuilder kbuilder =
> KnowledgeBuilderFactory.newKnowledgeBuilder();
>
> Died:
> // this will parse and compile in one step
> kbuilder.add(ResourceFactory.newClassPathResource("HelloWorld.drl",
> DroolsTest.class), ResourceType.DRL);
>
> LogCat:
> 01-02 13:13:17.684: E/AndroidRuntime(537): java.lang.RuntimeException:
> Unable to start activity
> ComponentInfo{com.versaggi.android.droolsandroidtest/com.versaggi.android.droolsandroidtest.DroolsAndroidTestActivity}:
> java.lang.NullPointerException
>
>
I've seen NPEs thrown up from down in the Drools gears when the DRL
resource could not be found. Make sure that
   ResourceFactory.newClassPathResource("HelloWorld.drl",
DroolsTest.class)

is != null.

I had to re-compile the CompositeClassLoader.java file and then reinsert it
> into the drools-api-5.1.0.M2.jar file to get past this issue:
>
> "A small modification is needed in org.drools.util.CompositeClassLoader.
> Apparently, the Android JVM doesn't allow null as the parent classloader
> so I changed that to super(CompositeClassLoader.class.getClassLoader())in the constructor, and that works fine."
>

Yes, that's come up in other Java environments as well, and IIRC been fixed
on the way towards 5.2.0. )There ought to be a closed JIRA, if s.o. cares
to look it up.)

-W
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