Parent ClassLoader may not be null
by Abhay B. Chaware
Hi
I am writing a drools based app. I am getting this error when I create an instance of KnowledgeBuilder
at line,
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
Here is the error. Can anyone tell what does this error mean ?
java.lang.NullPointerException: Parent ClassLoader may not be null
at java.lang.ClassLoader.<init>(ClassLoader.java:239)
at java.lang.ClassLoader.<init>(ClassLoader.java:226)
at org.drools.util.CompositeClassLoader.<init>(CompositeClassLoader.java:38)
at org.drools.util.ClassLoaderUtil.getClassLoader(ClassLoaderUtil.java:27)
at org.drools.compiler.PackageBuilderConfiguration.setClassLoader(PackageBuilderConfiguration.java:333)
at org.drools.compiler.PackageBuilderConfiguration.init(PackageBuilderConfiguration.java:165)
at org.drools.compiler.PackageBuilderConfiguration.<init>(PackageBuilderConfiguration.java:159)
at org.drools.compiler.PackageBuilder.<init>(PackageBuilder.java:210)
at org.drools.compiler.PackageBuilder.<init>(PackageBuilder.java:143)
at Org.drools.builder.impl.KnowledgeBuilderFactoryServiceImpl.newKnowledgeBuilder(KnowledgeBuilderFactoryS
at org.drools.builder.KnowledgeBuilderFactory.newKnowledgeBuilder(KnowledgeBuilderFactory.java:47)
at com.ts.DBconnector.readKnowledgeBase(DBconnector.java:125)
I also tried adding this
Thread.currentThread().setContextClassLoader( this.getClass().getClassLoader() );
But am still getting the same error ... please help !
-abhay
14 years, 11 months
Compatibility of serialized KnowledgePackages?
by Ansgar Konermann
Hi all,
does anyone know if KnowledgePackages which have been compiled and
serialized using Drools 5.0.1 can be de-serialized with 5.1.1 or 5.2.0.CR1?
What about the other way round, serializing with a more recent version
and de-serializing with an older version?
Are there any obstacles here due to a change in internal representation
of KnowledgePackages between versions, or is the serialized format
"designed" to be an exchange format even between versions?
Kind regards
Ansgar
14 years, 11 months
OWL and drools expert
by clement.pernot
Hi,
I want to use drools expert with OWL files and embedded this with a program.
Is it possible? If yes, how it's possible? I have search and didn't find
something, if someone can help, I will be grateful.
I know that EulerGUI take OWL files and can compile with drools expert, but
I want to embedded drools expert and OWL files in a program and I think that
it's impossible to make this with EulerGUI.
I don't know if a solution exist for embedded drools expert and OWL files
but a search for it.
Best Regards,
Clément
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14 years, 11 months
Looking for simple drools-camel (non-spring) example
by bjh6392
Since the drools pipeline is deprecated, I'm interested in putting together a
simple example using drools-camel that acts as a pipeline between a JMS
queue and Drools Fusion. The starting point would be no
transformation, just pull pojos out of a queue entrypoint and into a drools
endpoint using camel.
NOTE: We are not using Spring, so am looking for a java code version of how
to do this.
However, in the 5.1 or 5.2 M2 and CR distributions, or anywhere else I've
searched for that matter, I can find very little documentation or code
examples on drools-camel. The one snippet I did find:
http://lucazamador.wordpress.com/2010/07/22/drools-camel-integration/
uses some objects from the org.drools.grid.local library that don't seem to
exist in the 5.2 M2 or CR releases:
LocalConnection connection = new LocalConnection(); <=doesn't exist
ExecutionNode node = connection.getExecutionNode(); <=doesn't exist
node.setId("node");
Context jndiContext = new JndiContext();
jndiContext.bind("node", node);
CamelContext camelContext = new DefaultCamelContext(jndiContext);
Can anyone point me to some code snippets, examples, anywhere would be fine,
test cases, etc.
Literally hitting a brick wall on the web. I see the objects in the
drools-camel library that I know I need to use; DroolsPolicy,
DroolsEndpoint...
Thanks.
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14 years, 11 months
Parent ClassLoader may not be null
by abhay_bc
Hi
I am writing a drools based app. I am getting this error when I create an
instance of KnowledgeBuilder
at line,
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
Here is the error. Can anyone tell what does this error mean ?
java.lang.NullPointerException: Parent ClassLoader may not be null
at java.lang.ClassLoader.<init>(ClassLoader.java:239)
at java.lang.ClassLoader.<init>(ClassLoader.java:226)
at
org.drools.util.CompositeClassLoader.<init>(CompositeClassLoader.java:38)
at
org.drools.util.ClassLoaderUtil.getClassLoader(ClassLoaderUtil.java:27)
at
org.drools.compiler.PackageBuilderConfiguration.setClassLoader(PackageBuilderConfiguration.java:333)
at
org.drools.compiler.PackageBuilderConfiguration.init(PackageBuilderConfiguration.java:165)
at
org.drools.compiler.PackageBuilderConfiguration.<init>(PackageBuilderConfiguration.java:159)
at org.drools.compiler.PackageBuilder.<init>(PackageBuilder.java:210)
at org.drools.compiler.PackageBuilder.<init>(PackageBuilder.java:143)
at
Org.drools.builder.impl.KnowledgeBuilderFactoryServiceImpl.newKnowledgeBuilder(KnowledgeBuilderFactoryS
at
org.drools.builder.KnowledgeBuilderFactory.newKnowledgeBuilder(KnowledgeBuilderFactory.java:47)
at com.ts.DBconnector.readKnowledgeBase(DBconnector.java:125)
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14 years, 11 months
CEP : events not being expired when they should
by radai.rosenblatt
Hi.
this forum post relates to (at least) 2 drools issues: JBRULES-2881 and
JBRULES-2862.
while trying to verify the fixes (both issues are marked fixed in
5.2.0.CR1), i've created 2 drl files:
the 1st file tests event retention for length windows:
package contrived.example
import contrived.example.Event
import contrived.example.Fact
declare Event
@role(event)
end
rule "match event with fact"
when
Fact($id : id)
Event (factId==$id) over window:length(1) from entry-point "Event
Stream"
then
//do nothing
end
the test code for this looks something like:
session.insert(new Fact(...));
eventStream.insert(new Event(...));
session.fireAllRules();
clock.advance (1 year);
eventStream.insert(new Event(...));
clock.advance(1 year);
session.fireAllRules();
//1st event is still in memory at this point <--- bug?
the 2nd file tests the 2-events-from-window scenario in #2862:
package contrived.example
import contrived.example.Event
import contrived.example.Fact
declare Event
@role(event)
end
rule "match 2 events"
when
$e1 : Event () over window:time(15m) from entry-point "Event Stream"
$e2 : Event (this before $e1) over window:time(15m) from entry-point
"Event Stream"
then
//do nothing
end
the test code is something along the lines of:
session.insert(new Event(...));
clock.advance(1 minute);
session.insert(new Event(...));
session.fireAllRules();
clock.advance(1 day);
session.fireAllRules();
//both events still in memory at this point <-- bug?
i ran these tests using drools 5.2.0.CR1, and they both failed. am i doing
something wrong ? were the issued fixed later than JIRA indicates ?
i'm attaching the maven project i built for these tests (it has a few other
tests as well, not related to this port. the test cases that do relate to
this post are TestLengthWindowRetention and TestTwoInWindow, they both fail)
so other people can run them as well.
http://drools.46999.n3.nabble.com/file/n3028890/drools-cep-retention.zip
drools-cep-retention.zip
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14 years, 11 months
CEP : explicit @expires() vs window
by radai.rosenblatt
if i have the followng drl code:
package contrived.example
import contrived.example.Event
import contrived.example.Fact
declare Event
@role(event)
@expires(10s)
end
rule "match event with fact"
when
Fact($id : id)
Event (factId==$id) over window:time(15m) from entry-point "Event
Stream"
then
//do nothing
end
how long should an Event live in memory? 10 seconds or 15 minutes?
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14 years, 11 months
list operations in "then" part
by Simon Chen
Hi all,
I am always confused about what we can do in the "then" part of the rule.
In particular, I have problem duplicate a list. For example:
when:
$b: Book( "james" memberOf authors )
then:
Test fact = new Test();
fact.getList().addAll( $b.authors );
insert(fact);
end
The error message reads like this:
BuildError: Unable to build expression for 'consequence': [Error:
Failed to compile: 2 compilation error(s):
- (1,7) unqualified type in strict mode for: $b
- (1,12) unqualified type in strict mode for: authors]
What is the right way to do this?
Thanks.
-Simon
14 years, 11 months
Backward chaining
by Nirmal Fernando
Hi,
Is there any documentation available regarding Drools backward chaining?
Thanks.
--
Best Regards,
Nirmal
C.S.Nirmal J. Fernando
Department of Computer Science & Engineering,
Faculty of Engineering,
University of Moratuwa,
Sri Lanka.
Blog: http://nirmalfdo.blogspot.com/
14 years, 11 months
