How to write Hibernate query lang(HQL) in .DRL file
by zeeshan
Hi !
According to my requirement I need to fetch and Insert data from database
using Hibernate Query from .DRL file.
I have idea how to execute HQL in Plain Java class but according to my
requirement,I need to fire query to database from .DRL file which I tried
but unable to get output instead I was getting errors.
Can anyone suggest me process to execute Hibernate Query from DRL file
or please provide me some sample code or any link.
Thanks !!
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12 years, 11 months
[Drools Planner] Multi depot CVRP / CVRPTW
by Mats Norén
Hi,
I've been looking at the VRP example in Drools and I'm thinking about using
it for multi depot cvrp and / or capacitated vrp with time windows.
Has anyone else tried planner for these use cases and can maybe shed some
light on their implementation?
Regards,
Mats
13 years
"Rule-Id" for a Drools Rule
by harishtejwani
All:
We are using Drools to detect specific events/conditions in our system.
In the 'then' condition of Drools rule, we would like to persist the "Rule
Id" of the rule that created the specific event/condition
This is because all our reporting is based on "rules" as filters, where
users can look at exceptions by specific rules.
Is there a suggestion or sample as how can the "Rule Id" be persisted or
indicated in the then condition that is immutable or can be long-lived. The
current approach of using Rule Name itself as the ID is brittle as this can
be changed and suddenly all reports would break.
If we assign ID's to rules, where do we keep the mapping of RULE ID to
Rules. If we store rules in GUVRNOR is there a way we can get Rule Id's for
Rules?
Best regards
Harish Tejwani
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13 years
Implementing Refraction with Drools
by magaram
I believe we can inject in Refraction capabilities into Drools Rule Engine
using a simple Agenda Filter. I have tested this with test cases against
JRules and Drools and get similar results. Without the Refraction Agenda
Filter it loops infinitely as expected.
Please try it out and tell me what you think. I believe refraction is a much
needed feature of a forward chaining rule engine for commercial purposes.
Any feedback is deeply appreciated.
Here is what the code looks like
---------Agenda Filter---------------------------
package test;
import java.util.ArrayList;
import java.util.List;
import org.drools.runtime.rule.Activation;
import org.drools.runtime.rule.AgendaFilter;
/**
* This custom agenda filter injects refraction behavior into the rule engine
* @author Mukundan Agaram
*
*/
public class RefractionAgendaFilter implements AgendaFilter {
private List encounteredActivations = new ArrayList();
@Override
public boolean accept(Activation act)
{
//Check for a Refraction
if (encounteredActivations.contains(act))
{
//Remove from encountered activations for future firing
encounteredActivations.remove(act);
//return false so the rule is not selected as part of the refraction
return false;
}
//Otherwise add the rule to check for potential refractions in the future
encounteredActivations.add(act);
//select the rule to be part of the agenda
return true;
}
}
-----------------DRL------------------------
//created on: Jan 15, 2013
package test
dialect "mvel"
rule testFooBar1
salience 100
when
$foo : Foo()
$bar : Bar(y > 0)
then
$foo.setX(($foo.getX() + $bar.getY()));
System.out.println("Fired "+drools.getRule().getName())
update($foo);
end
rule testFooBar2
salience 150
when
$foo : Foo(x >= 6)
then
System.out.println("Fired "+drools.getRule().getName())
end
rule testFooBar3
salience 50
when
$foo : Foo(x >= 7)
then
System.out.println("Fired "+drools.getRule().getName())
end
----------------Runtime execution code--------------------------
package test;
import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseFactory;
import org.drools.builder.KnowledgeBuilder;
import org.drools.builder.KnowledgeBuilderFactory;
import org.drools.builder.ResourceType;
import org.drools.io.ResourceFactory;
import org.drools.runtime.StatefulKnowledgeSession;
public class TestFooBarMain {
private static void test()
{
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbuilder.add( ResourceFactory.newClassPathResource( "TestFooBar.drl",
TestFooBarMain.class ),
ResourceType.DRL );
if ( kbuilder.hasErrors() ) {
System.out.println( kbuilder.getErrors().toString() );
}
else
{
System.out.println("DRL parsing - success!");
}
KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
kbase.addKnowledgePackages( kbuilder.getKnowledgePackages() );
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
Foo foo1 = new Foo();
foo1.setX(6);
Bar bar1 = new Bar();
bar1.setY(3);
ksession.insert(foo1);
ksession.insert(bar1);
ksession.fireAllRules(new RefractionAgendaFilter());
}
/**
* @param args
*/
public static void main(String[] args) {
test();
}
}
----------------Facts-------------------------
package test;
public class Foo {
private int x;
private int y;
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
}
package test;
public class Bar {
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
private int x;
private int y;
}
Thanks,
Mukundan Agaram
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13 years, 1 month
Question about drools-spring in a multi-treaded container (like tomcat).
by Gurvinder Narula1
Hello all,
I've been reading up about drool-spring integration and have put together a simple project that wires together a KnowledgeBase and KnowledgeSession as follows :
<drools:resource id="GroupUnit" type="DRL"
source="file:/Users/drools/drools-spring-test/src/Rules/drls/GroupUnit.drl" />
<drools:resource id="GradeUnit" type="DRL"
source="file:/Users/drools/drools-spring-test/src/Rules/drls/GradeUnit.drl"" />
<drools:resource id="EvaluateUnit" type="DRL"
source="file:/Users/drools/drools-spring-test/src/Rules/drls/EvaluateUnit.drl"" />
<drools:grid-node id="node1" />
<drools:kbase id="kbase1" node="node1">
<drools:resources>
<drools:resource ref="GroupUnit" />
<drools:resource ref="GradeUnit" />
<drools:resource ref="EvaluateUnit" />
</drools:resources>
</drools:kbase>
<drools:ksession id="ksession" type="stateful" kbase="kbase1"
node="node1" />
Then in my Controller call, I 'AutoWire' in the StatefulKnowledgeSession as follows :
@Controller
@RequestMapping( value = "foo" )
final class FooController{
@Autowired
StatefulKnowledgeSession ksession;
@RequestMapping( method = RequestMethod.GET )
@ResponseBody
public String evaluateUnit() {
Unit unit = new Unit("030", "502", "C", "9484", "45", new String[] {},
null);
if (ksession != null) {
ksession.fireAllRules();
ksession.insert(unit);
ksession.fireAllRules();
return "<UnitCategory>" + unit.getUnitCategory() + "</UnitCategory>";
}
else
return "<message> stateful session is null</message>";
}
The main question that I have is that – is this solution thread-safe ? From what I understand of spring is that beans configured without any additional qualifiers are inherently singletons. And when deployed in a multi-theaded container like tomcat, Spring assumes that the beans being severed up a thread-safe. So from I have read is that KnowledeSessions are inherently not thread safe. So putting the 2 together, I leaning towards the assessment that this above solution is NOT thread safe and that if I do want it to be thread safe I should set the StatefulKnowledgeSession to 'prototype' and not leave it as a singleton.
Please let me know if I'm missing anything in my assessment here !
Thanks in advance,
Gurvinder
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13 years, 1 month
Compiled rules differ KnowledgeAgent vs ResourceChangeScanner
by lhorton
Version 5.2.0.Final. I have a DRL file that is loaded into my server using a
change set and Spring configuration. The file loads without error, and I am
able to read the compiled package and print the rule names to confirm they
did load; however, only one of the rules fires. Then I copy (hot-deploy)
the same DRL file to its server-side directory, and the Resource change
Scanner picks it up and reloads it. After reload, all the expected rules
execute.
My guess is that the Spring/KnowledgeAgent compilation is different than the
one done via the resource change scanner. Has anyone else seen this
behavior? Any suggestions for further trouble shooting?
I can attach the change set, spring config and drl file if needed.
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13 years, 2 months
