Re: [rules-users] Question about Drools Spring, StatelessKnowledgeSession and globals
by Patrick van Kann
Hello fellow Droolers,
A while ago I asked why the <drools:batch> element seemed to work
differently in the case of a StatelessKnowledgeSession and a
StatefulKnowedgeSession (see below).
I just wanted to update those interested with the answer and ask some
further questions, probably aimed at any developers who happen to be
reading.
I checked out the 5.1.1.34858 tag and had a look at how the Spring
integration works. I found that the reason that the global is not set in the
case of a StatelessKnowledgeSession is because the <spring:batch> element is
effectively ignored in the StatelessKnowledgeSessionBeanFactory, which lacks
the following code present in the StatefulKnowledgeSessionBeanFactory (in
the internalAfterPropertiesSet() method):
if ( getBatch() != null && !getBatch().isEmpty()) {
for ( Command<?> cmd : getBatch() ) {
ksession.execute( cmd );
}
}
So, either by accident or design the <spring:batch> element has no effect
when using a StatelessKnowledgeSession (but is perfectly allowable in the
XSD/Spring namespace).
So my questions are:
1) Is this the intended behaviour or a bug? On reflection, I am now not sure
the idea of a "batch/script" makes sense for a StatelessKnowledgeSession
since execute() is a one-shot method and any globals set this way would not
be available to later executions, which is what I was looking for.
2) If so, should the XSD be changed to disallow the batch element within a
stateless session (difficult, given that this is determined via the "type"
attribute) or should the documentation simply warn people that the
<spring:batch> element doesn't do anything if you set the type attribute to
stateless (somewhat confusing, I suppose)
3) If not, should the code above be added to the
StatelessKnowledgeSessionBeanFactory.internalAfterPropertiesSet() method?
4) Should there be another way to declare a global that isn't through the
batch element (one that would cause globals to be set via the
setGlobal(String, Object) method rather than using the SetGlobalCommand via
the execute() method.
I am happy to try and contribute something along these lines if I can get
some guidance as to what was actually intended.
Hope this helps and thanks again for Drools.
Patrick
=====================================
Hello,
I've been trying out the Spring integration package in Drools 5.1.1 and it
works really well, but I have run into one issue I can't figure out.
I've defined 2 knowledge sessions from the same knowledge base in the app
context - one stateless, one stateful but otherwise identical. They both
refer to a collaborator defined as a bean in the app context which is to be
used as a global in my rules. This is just an excerpt of my full Spring
context, the kbase definition itself is not an issue.
<bean id="applicantDao" class="com.acme.app.dao.impl.ApplicantDaoImpl" />
<drools:ksession id="statelessKSession" type="stateless"
name="statelessKSession" kbase="kbase">
<drools:batch>
<drools:set-global identifier="applicantDao" ref="applicantDao" />
</drools:batch>
</drools:ksession>
<drools:ksession id="statefulKSession" type="stateful"
name="statefulKSession" kbase="kbase">
<drools:batch>
<drools:set-global identifier="applicantDao" ref="applicantDao" />
</drools:batch>
</drools:ksession>
The issue is that this configuration works for the stateful but not the
stateless session, in the sense that the stateful session appears to have a
valid reference to the applicantDao object in the Globals object but the
stateless session doesn't.
<at> Test
public void testStatelessGlobal() {
Globals globals = statelessKSession.getGlobals();
Object global = globals.get("applicantDao");
Assert.assertNotNull(global);
}
<at> Test
public void testStatefulGlobal() {
Globals globals = statefulKSession.getGlobals();
Object global = globals.get("applicantDao");
Assert.assertNotNull(global);
}
The first test fails (the global variable is null) but the second passes. No
errors are thrown by Drools during the setup of the Spring container.
What am I doing wrong? Should I be able to define globals in this way for
stateless sessions? The XSD seems to indicate this is a valid configuration,
but it just doesn't work.
Is anyone else working with the Spring integration that can point out my
error here?
Many thanks,
Patrick
13 years, 4 months
Drools: Using Declared Types in Decision Tables
by David Smith
Hi,
I am trying to use a declared type in a decision table
but get an "Unable to resolve ObjectType" message.
The declared type is in a file types.drl,
I have a spreadsheet test.xls that has a Ruleset with
an import line for the declared type.
Is it possible to reference a declared type from a decision table?
Is it possible to declare a type in a decision table?
Thanks
David
13 years, 5 months
Drools Guvnor API information?
by Vikas Hazrati
Hi,
I am looking at using Guvnor for our project where users would be creating
rules using our UI. For this i need to add / modify rule or any asset for
that matter using an api.
Unfortunately, i could not find enough documentation to suggest the best way
to use the REST api, which I guess is provided by Guvnor. Could someone let
me know the location of where i can get some information for this api. I
also see that the issue GUVNOR-1080
(https://issues.jboss.org/browse/GUVNOR-1080) is marked resolved so the api
should exist right? or that we cannot access it remotely until we have the
Atom Pub Interface done?
Help appreciated .
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13 years, 7 months
java.lang.OutOfMemoryError: Java heap space
by vdelbart
Hello,
In my tests of the 4.0.3, I have some : java.lang.OutOfMemoryError.
So, I try a simple test with 10.000 sequential execution of 1 rule with no
context and just a workingmemorylogger and I have the error :
java.lang.OutOfMemoryError: Java heap space
My code is :
public class ExecReglesMemotyTest
{
private static final Reader DRL = new
InputStreamReader(ExecReglesMemotyTest.class
.getResourceAsStream("/rules/exemple.drl"));
private static final String FICHIER_LOG = "session";
/**
* @param args
*/
public static void main(String[] args)
{
try
{
PackageBuilder builder = new PackageBuilder();
builder.addPackageFromDrl(DRL);
RuleBase ruleBase = RuleBaseFactory.newRuleBase();
ruleBase.addPackage(builder.getPackage());
for (int i = 0; i < 10000; i++)
{
StatefulSession session = ruleBase.newStatefulSession();
WorkingMemoryFileLogger logger = new WorkingMemoryFileLogger(session);
logger.setFileName(FICHIER_LOG);
session.fireAllRules();
logger.writeToDisk();
session.dispose();
}
}
catch (Exception e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
with this rule (doesn't matter):
#created on: Fri Nov 09 15:48:45 CET 2007
package initPackage
#list any import classes here.
rule "ERG9"
when
then
end
I try this in 4.0.1, and it's working (no OutOfMemoryError)
What's the problem ?
thanks for any information,
V.
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13 years, 8 months
Challenge! Using javassist and drools presents an issue with drl
by markricard
In order to make writing drl files easy and not requiring writers to be
developers, I have written some JavaAssist code that dynamically creates a
subclass and new methods in memory.
If for example there is a REAL java class called 'com.foo.Instance'. Via
javasssist, I create a new in-memory subclass called 'com.foo.InstanceEx'.
The new class dynamically creates a new getter called getFoo(). The drl
writer would like to directly reference 'foo' in the drl file like so:
when
i : Instance(foo == 'fee')
The problem is, in order to reference foo, I would need the drl file to do
this:
import com.rrd.xspace.drools.InstanceEx;
But I cannot do that because InstanceEx does not exist at runtime. The
error I get, which is an obvious one, is "Unable to create Field Extractor
for 'foo' of '[ClassObjectType class=com.foo.Instance]' in rule 'Test' :
[Rule name='Test']"
Is there a way to include a dynamic import of a JavaAssist class while I am
constructing the KnowledgeBase instances to run the rules so that I can
reference that new method?
I would hope to have something similar to:
KnowledgeBuilder kbuilder = ....
kbuilder.addImport("com.foo.InstanceEx")
or
kbuilder.addClass(Class.forName("com.foo.InstanceEx"))
Any help GREATLY appreciated.
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14 years, 1 month
Re: [rules-users] Error running Drools 5.0 HelloWorldExample on WebSphere 6.1
by Blythe, Marshall
A quick follow-up: this error occurs only when I have rules using the MVEL dialect. I rewrote the MVEL rule in the HelloWorld.drl to use the Java dialect, and now the problem is gone. I may need to raise this issue on the MVEL mailing list instead.
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14 years, 4 months
Difference between Rule Base and Knowledge Base
by Swapnil Sawant
Hi,
I had a very basic doubt. 'Rule Base' and 'Knowledge Base' are two different concepts (may be from implementation point of view )?
I got this doubt when I was going through section '1.4.7.2. Drools execution server' of drools guvnor (v5.0) where it was written like :
The drools execution server (drools-server) module is a war which you can deploy to execute "knowledgebases (rulebases)" remotely for any sort of client application
The thing is that , I have created Knowledge base from changeset.xml as follows :
kagent = KnowledgeAgentFactory.newKnowledgeAgent( "MyRuleAgent" );
kagent.applyChangeSet( ResourceFactory.newUrlResource( changesetUrl ) );
kbase = kagent.getKnowledgeBase();
Now if I wish to get Rule Base corresponding to my changeset(or rather my DRL file) using 'this kbase object' , how can I do that ?
Thanks,
Swapnil Sawant
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14 years, 4 months
drools flow - how to crate a human task form?
by gs76pl
hi,
What is the best way of creating some UI for human tasks with an input form?
I've a sample process with a human task that should update some values in
the process. I had a look into API of a task and the only thing i can find
there is 'content' which i'm not really sure about (is it the place where
for instance HTML UI should be created?) Is there any way to create this
form with some additional actions like : claim/fail etc?
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14 years, 5 months
