Trying to get Eclipse Java code to call Guvnor
by John Peterson
I'm using the example code from the Red Hat Magazine -
http://magazine.redhat.com/2008/08/12/jboss-drools-how-to-tuning-guvnor-
part-1/ - to try to get the sample code to work, but I keep getting the
following error:
Exception in thread "main" java.lang.NullPointerException
at java.util.Properties$LineReader.readLine(Unknown Source)
at java.util.Properties.load0(Unknown Source)
at java.util.Properties.load(Unknown Source)
at
org.drools.agent.RuleAgent.loadFromProperties(RuleAgent.java:299)
at org.drools.agent.RuleAgent.newRuleAgent(RuleAgent.java:256)
at test.GuvnorTest.main(GuvnorTest.java:15)
It appears to be unable to find my 'Guvnor.properties' file, but I have
it in the classpath (I actually have it in several different places on
my C: drive as I tried to figure out why it couldn't find it). Does
anyone have any thoughts on what's wrong here?
I'd appreciate any guidance. It seems like this should be a simple
answer but I haven't been able to figure it out.
15 years, 6 months
About for and inheritance
by Chris Woodrow
Hi,
I recently find out a few issues using for, and I wanted to share it with
you. I made a simple exemple to illustrate my purpose.
My classes are (I did not represent accessors & constructors):
public class Cheese {
protected String name;
}
public class FrenchCheese extends Cheese{
private String smell;
}
public class Person {
private Cheese likes;
}
Here is my rule set :
package rules
rule "likes cheese"
when
$person : Person ()
Cheese( ) from $person.getLikes()
then
System.out.println("likes cheese");
end
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
First test :
Cheese cheese = new FrenchCheese("good", "camembert");
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
Wich is expected...
Second test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
That's the first strange thing. As far as I am concerned, rule "likes french
cheese" should not match (since a Cheese is not a FrenchCheese).
I made a change to the second rule :
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( smell == "good" ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
Third test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
output :
It throwed an exception : Exception in thread "main"
java.lang.ClassCastException: rules.Cheese
I am not saying the ClassCastException is not to expect in such a case but I
think I would simply expect it not to match (as far as a Cheese is not a
FrenchCheese).
Chris
15 years, 7 months
Upload an existing .drl for the Guvnor dynamically
by Vandewilly
Is there any api available that allows me to load an existing file drl for
the Guvnor repository. In my case, I can not upload through the web
interface, only in a dynamic way through a java class.
--
Vandewilly Oliveira
15 years, 7 months
Drools 4.0, Support for multiple pattern in accumulate source pattern
by Juergen
It appears as if accumulate does support only a single pattern CE as
source pattern, e.g.:
Number() from accumulate(
Cheese(
price : price
),
sum( price )
)
Is it possible to have more than one pattern in the source pattern, e.g.:
Number() from accumulate(
Cheese(
price : price,
type : type
)
Person(
favouriteCheese == type,
age > 30
),
sum( price )
)
The same could be said for collect, but there the problem to specify
which item of a matching tuple is to be collected, but this could be
handled recreating collect via accumulate, e.g.:
Collection() from accumulate(
cheese : Cheese(
type : type
)
Person(
favouriteCheese == type,
age > 30
),
collect( cheese )
)
15 years, 7 months
BuildError: Unable to resolve ObjectType
by BS
Hi all,
I'm quite new to Drools and have a problem with the guided editor of the
Eclipse plugin. I'm using Drools 5.0.1.
These are the two BuildErrors for "TestGuided.brl" in Eclipse:
1) BuildError: Unable to build expression for 'consequence': Failed to
compile: 1 compilation error(s): - (1,1) unqualified type in strict mode
for: p ' update( p );
2) BuildError: Unable to resolve ObjectType 'Produkt'
In "drools.package" I have all necessary imports and also the package
statement. This is the BRL source of "TestGuided.brl":
<rule>
<name>TestGuided</name>
<modelVersion>1.0</modelVersion>
<attributes/>
<metadataList/>
<lhs>
<fact>
<factType>Produkt</factType>
<boundName>p</boundName>
</fact>
</lhs>
<rhs>
<modify>
<fieldValues/>
<variable>p</variable>
</modify>
</rhs>
</rule>
When I use the generated DRL output of the guided editor in a DRL file, I do
not get any error message. The DRL file looks like this and compiles
perfectly in Eclipse:
package com.test
rule "TestGuided"
dialect "mvel"
when
p : Produkt( )
then
update( p );
end
Adding the BRL from above to Guvnor does not throw any error. The BRL
validates and compiles perfectly in Guvnor.
So, why is it only in the guided editor of Eclipse not working but in the
guided editor of Guvnor as well as DRL file? Maybe something in my
configuration is errorneous?
Any help is appreciated, many thanks
Bernd
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15 years, 8 months
Blurring the lines of jBPM and Drools
by keithnielsen
I have been researching both jBPM and Drools for sometime now and am
wondering what the future holds for jBPM. This is based on my research of
Drools 5, which is bringing what I would consider more BPM constructs into
the core engine, things such as Wait States, Human Tasks, etc. One of the
main things I don't see yet is the whole persistence and support of long
running processes. My question is will the trend with Drools continue,
eventually consuming jBPM?
I must say that my perception is that Drools is more active which makes me
wonder if I should go with Drools hoping that it builds out more BPM
features going forward.
Thanks
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15 years, 9 months
Resuming a simple process involving human task
by Touma
Hi all,
For the past few weeks I've been trying to get a simple drools flow example
involving human tasks up and running. I've done quite a bit to the point
that my session, process, task and workitems are being persisted in the
database. Here is what my flow looks like:
Start -> Ruleflow -> Decision node -> Human Task -> Printing Node -> End
The work item handler for the Human task simply performs the task of
persisting the Task instance. After reaching the Human Task, the flow stops
and the state is persisted. But how would I go about restarting/resuming the
flow so that the 'Printing node' is reached? I've tried using the
loadStatefulKnowledgeSession(sessionId) to load the session but querying the
list of all the processes for the given session returns an empty list. Ditto
with the list of all the process events. I have all the ID's with me
(workitem, process, task, session) but am pretty confused as to how these
can be put to use to resume my suspended workflow.
Any pointers would be much appreciated. TIA.
Peace,
/T\
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15 years, 10 months
Chained Rules
by djb
Hi all,
I know there are some basic ways to chain rules together, by setting flags
in consequences that are checked in the conditions of other rules...
but in a large system based on rule templates, where thousands of rules are
generated, it is not feasible to chain rules in this manner, especially when
they are chained in a somewhat arbitrary fashion
(eg. True if Rule 130 AND Rule 200 AND Rule 480 fire)
has anyone had this situation before? would I need to execute this as a
post-processing step? or, is there any design pattern that will allow rules
to be chained, preferably in a manageable way?
regards,
Daniel
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15 years, 10 months
