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
14 years, 11 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
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, 1 month
Decision Tree input?
by Wilson O Ojwang
All,
Is there something in the works to support Decision Tree Inputs in
addition to Decision Table?
Regards
Wilson
15 years, 5 months
java.lang.NoSuchMethodError on every Action node
by Ana F Santos
Hi everyone.
I've been trying to use Drools for the past month, and sometimes I have
problems I can't guess anymore how to solve.
This time, every action I try to insert in a ruleflow, I receive a
java.lang.NoSuchMethodError. I'm even trying a really simple ruleflow with
just one simple action - like System.out.println("Test"); - and all I get
is a java.lang.NoSuchMethodError.
[
The stack trace:
java.lang.NoSuchMethodError:
br.com.pst.packages.ruleflows.Process_br_com_pst_packages_ruleflows_0.action0(Lorg/drools/spi/KnowledgeHelper;Lorg/drools/spi/ProcessContext;)V
at
br.com.pst.packages.ruleflows.Process_br_com_pst_packages_ruleflows_0Action0Invoker.execute(
Process_br_com_pst_packages_ruleflows_0Action0Invoker.java:20)
at
org.drools.workflow.instance.node.ActionNodeInstance.internalTrigger(
ActionNodeInstance.java:54)
at org.drools.workflow.instance.impl.NodeInstanceImpl.trigger(
NodeInstanceImpl.java:111)
at
org.drools.workflow.instance.impl.NodeInstanceImpl.triggerConnection(
NodeInstanceImpl.java:142)
at
org.drools.workflow.instance.impl.NodeInstanceImpl.triggerCompleted(
NodeInstanceImpl.java:128)
at
org.drools.workflow.instance.node.StartNodeInstance.triggerCompleted(
StartNodeInstance.java:49)
at
org.drools.workflow.instance.node.StartNodeInstance.internalTrigger(
StartNodeInstance.java:41)
at org.drools.workflow.instance.impl.NodeInstanceImpl.trigger(
NodeInstanceImpl.java:111)
at
org.drools.ruleflow.instance.RuleFlowProcessInstance.internalStart(
RuleFlowProcessInstance.java:16)
at org.drools.process.instance.impl.ProcessInstanceImpl.start(
ProcessInstanceImpl.java:185)
at
org.drools.workflow.instance.impl.WorkflowProcessInstanceImpl.start(
WorkflowProcessInstanceImpl.java:230)
at org.drools.common.AbstractWorkingMemory.startProcess(
AbstractWorkingMemory.java:1639)
at org.drools.common.AbstractWorkingMemory.startProcess(
AbstractWorkingMemory.java:1604)
at org.drools.impl.StatefulKnowledgeSessionImpl.startProcess(
StatefulKnowledgeSessionImpl.java:267)
at br.com.pst.packages.ServicePackages.main(
ServicePackages.java:99)
]
Actually, the beginning problem was with my project, with a process and
subprocess. The subprocess works fine, but the main process throws a
java.lang.NoSuchMethodError always on any node I put after a specific
RuleFlowGroup node. Everyting used to work before, but when I begin to
enlarge it, nothing seems to work anymore. And, as I told, I can't always
guess the exact problem as the thrown exceptions are very generic.
Hope anyone could help me!
Thanks a lot
ANA FLÁVIA FONSECA DOS SANTOS
Analista de Desenvolvimento de Software
PST Eletrônica S/A
Phone: +55 19 3787 6379
aflavia(a)pst.com.br
www.pst.com.br
www.positron.com.br
15 years, 5 months
KnowledgeAgent doesn't load dsl files and dslr file from a change-set correctly
by Pritham
I have a folder in classpath:
dsl/global.dsl
rules/section-A.dslr
rules/section-A/page-1.dslr
I create a knowledge base like this:
public KnowledgeBase createKnowledgeBase() throws DroolsParserException,
IOException {
KnowledgeBuilder knowledgeBuilder = KnowledgeBuilderFactory
.newKnowledgeBuilder();
knowledgeBuilder.add(ResourceFactory
.newClassPathResource("dsl/global.dsl"),
ResourceType.DSL);
knowledgeBuilder.add(ResourceFactory
.newClassPathResource("rules/section-A.dslr"),
ResourceType.DSLR);
knowledgeBuilder.add(ResourceFactory
.newClassPathResource("rules/section-A/page-1.dslr"),
ResourceType.DSLR);
if (knowledgeBuilder.hasErrors()) {
throw new RuntimeException(knowledgeBuilder.getErrors().toString());
}
KnowledgeBase knowledgeBase = KnowledgeBaseFactory.newKnowledgeBase();
knowledgeBase.addKnowledgePackages(knowledgeBuilder.getKnowledgePackages());
return knowledgeBase;
}
// code
knowledgeBase = createKnowledgeBase();
session = knowledgeBase.newStatefulKnowledgeSession();
// insert facts
session.fireAllRules();
session.dispose();
The above code works and I can get a unit test to work that processes rules
accordingly. I can see my dslr converting to a drl using the "drl viewer"
correctly (provided I temporarily place the dsl file in the same location
since expander doesn't accept a relative path).
The problem, however is when I use a change-set.xml and a KnowledgeAgent,
things don't work
code for loading via knowledgeAgent
public static KnowledgeBase loadKnowledgeBase() throws
DroolsParserException, IOException {
agent = KnowledgeAgentFactory.newKnowledgeAgent("msll agent");
agent.applyChangeSet(ResourceFactory.newClassPathResource("change-set.xml"));
return agent.getKnowledgeBase();
}
<change-set xmlns='http://drools.org/drools-5.0/change-set'
xmlns:xs='http://www.w3.org/2001/XMLSchema-instance'
xs:schemaLocation='http://drools.org/drools-5.0/change-set.xsd'
>
<add>
<resource source='classpath:dsl/' type='DSL' />
<resource source='classpath:rules/' type='DSLR' />
<resource source='classpath:rules/section-A/' type='DSLR' />
</add>
</change-set>
I get the following generic drools errors:
ERR 103] Line 4:0 rule 'rule_key' failed predicate:
{(validateIdentifierKey(DroolsSoftKeywords.RULE))}? in rule[7,0]: [ERR 101]
Line 7:0 no viable alternative at input 'import' in rule Con in rule
attribute
...
...
The rules are same, folder location is the same. I believe that drools has a
problem resolving path (expander global.dsl) from the dslr file when using a
KnowlegeAgent since in the earlier strategy, one could build a dsl into the
knowledgeBuilder directly from the classpath.
Pl suggest.
--
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15 years, 5 months
Debug as within Eclipse
by chris richmond
I used the upate site to update my Eclipse Galileo IDE with the drools
tools, created a new drools project, had it add the hello/goodbye test class
and pointed my workspace to the 5.1M binaries. It runs fine, but when I
Debug As -> Drools Application I get the following errors. I get this error
for any drools project I try to debug as Drools application within Eclipse.
Any ideas?
Thanks,
CHris
FATAL ERROR in native method: JDWP No transports initialized,
jvmtiError=AGENT_ERROR_TRANSPORT_INIT(197)
ERROR: transport error 202: connect failed: Connection refused
ERROR: JDWP Transport dt_socket failed to initialize, TRANSPORT_INIT(510)
JDWP exit error AGENT_ERROR_TRANSPORT_INIT(197): No transports initialized
[../../../src/share/back/debugInit.c:690]
15 years, 5 months
MVEL strict mode -- when, why?
by Barry Kaplan
I have never gotten any of my rules to compile using mvel strict mode. If I
leave the default I get spews of error messages that I can't make any sense
of. For example with:
---
package systeminsights.plugin.core.schedule
rule "foo"
when
eval(true)
then
// noop
end
---
I get messages like
[Error: Failed to compile: 3 compilation error(s):
- (1,21) unqualified type in strict mode for: plugin
- (1,26) unqualified type in strict mode for: core
- (1,35) unqualified type in strict mode for: schedule]
[Near : {... Unknown ....}]
^
[Line: 1, Column: 0]
If I set strict mode to false all is good.
So, what is actually going on with strict mode? And how does one interpret
messages such as the above?
-barry
--
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15 years, 6 months
Exception handling policy
by Gerret Hansper
Hello,
I have got a question about Exception handling policy in Drools 5.0.
My issue is a case where a client application triggered rule execution on the
server, which was throwing a ConsequenceException.
The client, not having drools libs in its classpath, then had a
ClassNotFoundException.
I would therefore want to catch the ConsequenceException on the server and throw
an Exception with its cause.
I am not sure however if ConsequenceException.getCause() would always yield a
non-drools Exception or if that might be another drools type.
Also, is it always a ConsequenceException that gets thrown from a session or can
there be other Exception types?
Thanks,
Gerret
15 years, 6 months
Drools Roadmap - Planned Release 5.1 release date
by McDonald, Daniel
Hi,
I was wondering if there is a planned release date for Release 5.1?
Thank you,
Daniel McDonald
Fidelity National Information Services - Research & Development
Office phone: (972) 691-6593
Mobile phone (214) 697-8163
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15 years, 7 months
