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BusinessRuleTask - deploy error

rdenner

Hi,

I want to use the new BusinessRuleTask element for a test.
I defined a rule (drl) file, which I include in the Business Archive (bar).
I modeled a simple process and two forms. The BusinessRuleTask
executes 2 rules, gets 2 input variables and delivers 1 result variable.

Here is an example of one of my rules:

rule "salarycheck" 

when
    (salary > 3000) && (age < 30)
then
    ruleOutput = "pattern1";
end
‍‍‍‍‍‍‍‍‍

I wanted to deploy the bar file, but I get the error:
java.lang.NoClassDefFoundError: org/drools/runtime/rule/AgendaFilter

Do I need the Drools package for working with the BusinessRuleTask?
Does anyone have a simple example?

Thanks & Regards,
Rainer.

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Comments

rdenner

Hi,

I deployed my bar file now via activiti-probe. The import went fine.

The first thing I noticed in activiti-explorer was the missing BusinessRuleTask element
in the graphical represenation which I called with Show Diagram. But thats no problem.

I started the process, filled out the first form, which is referenced by the start event.
After leaving this form, I get an error:
02080004 Wrapped Exception (with status template): deployment xxxx doesn't contain any rules

I checked the bar file before deployment, there is a drl file with my rules in this package.

Does anyone have an advice?

I also attach my bar file which includes the process, 2 forms and the rule file.
(Bar extension is not allowed, so I renamed the file to zip)

Regards,
Rainer.

activiti-rules-demo.zip

trademak

Hi,

Thanks for providing the BAR file example.
I'll look into this, this evening.

Best regards,

trademak

Hi,

I've noticed a couple of things that you should think about when using the business rule task:

1. The drools-api, drools-compiler, drools-core and mvel2 jar files are missing from the activiti-rest application, so you have to add those manually.
2. In the activiti-cfg.xml inside the activiti-cfg.jar in the activiti-rest application you have to include the following property:

<property name="customPostDeployers">
 <list>
 <bean class="org.activiti.engine.impl.rules.RulesDeployer" />
 </list>
</property>

This is missing in the userguide, but needs to be in the activiti-cfg.xml file to get the rules deployed.

3. Make sure you create a valid drl file. It's important to use Javabeans as input variables and output variables.
So maybe you could create a Javabean with salary and age as attributes. The same for the result variable.
4. I saw the bpmn20.xml in your BAR file is inside the diagrams folder. It's better to have it at the root of the BAR file.

With these changes it should work. Let me know if it works for you.

Best regards,

rdenner

Hi,

thanks for your reply and the detailed explanation.

I have only one question for understanding. I have to use Javabeans to map the processvariables to drools.
But how do the Javabeans get the processvariables? Do I have to make a Delegate for input and output variables to
initialize the Javabeans? The Delegate could be created with a Service Task or as a Listener.

Regards,
Rainer.

trademak

Hi,

Right, a simple way to do this is to create a java service task before the business rule task is invoked to set the process variables in the java bean and store the java bean as a new process variable. Then the output of the ruleset should also be a javabean.

Best regards,

rdenner

Hi,

thanks for your affirmation. I will test this solution and give you feedback.

Regards,
Rainer.

rdenner

Hi,

I made two beans for input and output variables. I also made a delegate for
creating the beans. But I think my rule never gets fired. I made several tests
but without success.

I attached my small eclipse test project. Perhaps you can see where I made an error.

Thanks,
Rainer.

activiti-rules-demo.rar

trademak

Hi,

I made a couple of changes and now it works. You can find the project (using the Activiti Designer) attached.
The changes include:

1. input variable should be ${ruleInput}
2. drl file is changed
3. I've added another service task to get the right output variable.

Best regards,

activiti-rules-demo_0.zip

rdenner

Hi,

thanks for your effort.
It works all now.

Regards,
Rainer.

vasanthmiste

Hi,
I have done all the steps that mentioned in this thread, but still i am getting 'deployment xxxx doesn't contain any rules' exception.

I tried with your rule demo package also, i am using Activiti5.7.

Do i need to anything other than mentioned here..

trademak

Hi,

Did you try this out on the Activiti Explorer?
You can find a full example about using the business rule tasks here (http://code.google.com/p/activitiinaction/). A lot more details are in chapter 12 of the Activiti in Action book.

Best regards,

vasanthmiste

Yea, i did it explorer only. Do we need to make any changes in the activiti applications like config file changes..

Could you please share the steps to deply and run the demo project[that you attached in this thread] once after the successful setup of activiti.

This is would be greatly helpful..

trademak

I would recommend reading chapter 12 of Activiti in Action, because it's all explained there.

Best regards,

mikedias

Sorry to resurrect the topic, but I am starting development using the Activiti and I like it.

However, I found strange create a Service Task to initialize a bean with the Process Variables and send the bean to Drools.

Can I just pass the DelegateExecution object with all variables to Drools? Will be more flexible.

Thanks.

ronald_van_kuij

If you do not use the existing businessrule task but create your own service task, you might get this working. But the delegate execution is such a 'low level' object that it is not common to do this.

mikedias

Ronald, thanks for answer!

Create my service task is a interesting way. I will test this.

But I think that the default behavior of the Business Rule Task should be send all Process Variables to Drools into a wrapper. This is just my impression about this, please correct me if I'm wrong!

Thanks.

trademak

Hi Mike,

Well, that's certainly a possibility. If you don't specify input variables automatically all variables of the execution are added to the Drools execution.
Let me know if that's what you are looking for.

Best regards,

ronald_van_kuij

Hmmmm, personally I don't like these kinds of defaults…

trademak

Hi,

We could also add an additional attribute like copyProcessVariables that defaults to false and that you can set to true.

Best regards,

mikedias

Hi Tijs!

I think that the Process Variables could be inserted into Drools together with the Input Variables. So, you can combine your beans and the Process Variables in your rules.

My objective is allow writing business rules without Java code.

Thanks!

mikedias

Hi,

I added this in the BusinessRuleTaskActivityBehavior.java:

 ksession.insert(execution.getVariables()); And the rule below works fine:

<br>import java.util.Map;<br><br>rule "ChoseGroup"<br> when<br>&nbsp;&nbsp; Map( this["actionType"] == "tech" )<br> then<br>&nbsp; System.out.println("The group chosen is engineering");<br>&nbsp; insert("engineering");<br>end<br>

In the "Candidate Group" of the next task, I assign ${ruleOutput} and this works too.

But I have 2 questions:
1) All the objects inserted in the ksession go to output variable. Could I to send only the output produced by the rule? This is a good approach?
2) The use of BusinessRuleTask is a better approach to dynamically choose users or groups based in a decision table? My problem is: given a process variable, choose the user / group based in a rule that can be changed any time.

tombaeyens

In many processes, there are a lot of process variables, some of which can be large. With the implementation you propose, all the process variable data has to be fetched from the DB and deserialized into objects. Even if none of these variables are used, all that overhead is performed.

I suppose there is a workaround for accessing variables in the current implementation as well.

If I recall correct, there is a way to implement lazy loading of these variables in drools. I think it might be through something called global variables in drools, but it's been a while since I checked that out. A solution that includes lazy loading would be a nice contribution.

tombaeyens

The solution to customize the drools globals so that you can do lazy loading of the variables can be done with this api i believe:

knowledgeRuntime.getGlobals().setDelegate(customGlobalsImplWithLazyLoadingOfVariables);
http://docs.jboss.org/jbpm/v5.1/javadocs/org/drools/runtime/Globals.html#setDelegate(org.drools.runtime.Globals)

mikedias

Interesting Tom, but the Drools have some restrictions about the globals:

"Globals are not inserted into the Working Memory, and therefore a global should never be used to establish conditions in rules except when it has a constant immutable value. The engine cannot be notified about value changes of globals and does not track their changes. Incorrect use of globals in constraints may yield surprising results - surprising in a bad way."
http://docs.jboss.org/drools/release/5.4.0.Final/drools-expert-docs/html/ch04.html#d0e4482

I think that the variables in the rule scope is immutable, but I don't have sure.

bernd_ruecker

Hi Mike.

You can (at kleast since 5.10) attach a expression or delegate to the Business Rule Task. We consider it best practice to implement your own delegate to steer Drools, then you have full control over what you are doing and can easily encapsulate it behind some service interface or the like… Then you can insert all data you want 🙂

mikedias

Hi Bernd, thanks for answer!

In my Activiti Eclipse Designer 5.9.3 I can't see this option. The delegate can be assigned in the "Input variables" field?

However, I think that the process variables should be accessible for all rules in any situation. Then we have more options to build a complex rule without effort.

bernd_ruecker

Hi Mike.

From the engine point of view it looks still like a service task: http://svn.codehaus.org/activiti/activiti/trunk/modules/activiti-engine/src/test/resources/org/activiti/engine/test/bpmn/ruletask/RuleTaskTest.testJavaDelegate.bpmn20.xml.

For the Activiti Designer I actually do not know as we use a different eclipse designer (https://app.camunda.com/confluence/display/foxUserGuide/fox+designer) 😉

Sorry & cheers
Bernd

trademak

Hi Mike,

Yes I think we could add an attribute to the business rule task to copy all process variables to the Drools context.
I disagree with Bernd that a service task is the best option. Of course you can implement it exactly as you want in that case, but you also need more Drools knowledge.

Best regards,

bernd_ruecker

Hi Tijs.

I think if you use Drools you need Drools Know-How, there is no way around it. And the API is easy enough to do that, the problem normally is the DRL/Excel/SDL whatever syntax… And the current implementation is too limit for real live use cases in my opinion, but I still think that is not an issue, since you can implement it yourself in the way you want to have it. Perfectly fine 🙂

But OK, we do not have to reach some sort of agreement, that is what we recommend and we actually do not support the Drools implementation of the Business Rule Task in the EE version of fox…

Cheers
Bernd

mikedias

Hi Tom and Tijs,

I changed again the BusinessRuleTaskActivityBehavior.java. Now I insert in the Working Memory the ActivityExecution object that, if I understand correctly, already is a impl of lazy loading of the variables:
 FactHandle executionFact = ksession.insert(execution); So, the following rule works fine:

<br>import org.activiti.engine.impl.pvm.delegate.ActivityExecution;<br><br>rule "Rulez"<br> when<br>&nbsp; ActivityExecution(getVariable("inputVar") == "myInput")<br> then<br>&nbsp; System.out.println("Rulez executed");<br>&nbsp; insert("RulezExecuted");<br>end<br>

And after execution, I remove the execution from the Working Memory to clean the output:
 ksession.retract(executionFact); What do you think?

Cheers,