Passing Class objects to Drools Rules (drt) file - drools

Question

I'm using Drools Template for decision making, I have created instance of class and passed the class objects to Kie session using insert
In the drt file, I tried to compare the Template columns with Class objects and certain parameters have passed threshold , then setting the Priority based on the value in the Template file
Format of the Template file (Excel)
Parameter Mountpoint Threshold Severity
Disk /root 80 MINOR
Disk /tmp 90 MAJOR
My class Capacity {
private String component;
private String subComponent;
privat Integer value;
public String getComponent() {
return component;
}
public void setComponent(String component) {
this.component = component;
}
public String getSubComponent() {
return subComponent;
}
public void setSubComponent(String subComponent) {
this.subComponent = subComponent;
}
public Integer getValue() {
return value;
}
public void setValue(Integer value) {
this.value = value;
}
public Capacity()
{
super();
this.component = component;
this.subComponent = subComponent;
this.value = value;
}
}
In another class, I'm initiating KieSession and injecting the capacity Class objects and loads the Templates file
Drool
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
KieSessionConfiguration sessionConfig = KnowledgeBaseFactory.newKnowledgeSessionConfiguration();
sessionConfig.setOption( ClockTypeOption.get( ClockType.PSEUDO_CLOCK.getId() ) );
try {
loadRuleTemplate(DATA_FILE, RULE_TEMPLATE_FILE, "OperationalMeasurement", 2, 1);
} catch (IOException errorMsg) {
log.error(errorMsg.getMessage()); }
InternalKnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
kbase.addPackages(kbuilder.getKnowledgePackages());
KieSession kieSession = kbase.newKieSession(sessionConfig, null);
sessionClock = ksession.getSessionClock();
ksession.insert(Capacity);
ksession.fireAllRules();
ksession.dispose();
Rules file
template header
Parameter
Mountpoint
Threshold
Severity
package com.test.drools;
dialect "java"
template "OperationalMeasurement"
rule "Check_Threshold_#{row.rowNumber}"
ruleflow-group "capacityManagement"
salience 500
when
$capacity: Capacity(component == "#{Parameter}" && subComponent == "#{Mountpoint}" && value >= "#{Threshold}")
then
System.out.println("Thresold cross for Component and Priority is set " + #{Severity}");
end
end template
When i run this, component is treated as literal string instead of Capacity class variable and though i dont get any error , it simply prints all the contents of the drt file in the console.
And I dont seems to get the Sysout statements

Answer 1

component is treated as literal string instead of Capacity class variable
Not sure what you mean by that. what "component" is being treated as a literal?
According to the generated rule you added as a comment, there are some errors in the rules being generated:
System.out.println("Thresold crossed for Component::" +component + " and Priority is set " + Major");
In the line above, "component" is expected to be a variable, but there is no variable with that name. There is also a missing quote before the "Major" string.
I would suggest you to change your template to something like this:
rule "Check_Threshold_#{row.rowNumber}"
ruleflow-group "capacityManagement"
salience 500
when
$capacity: Capacity(component == "#{Parameter}" && subComponent == "#{Mountpoint}" && value >= "#{Threshold}")
then
System.out.println("Threshold cross for Component:: #{Parameter} and Priority is set to #{Severity}");
end
end template
That should generate valid DRL.
One other thing that worth mentioning is that for some weird reason that I never fully understood, Drools will not complain if there are errors in your Knowledge Bases (i.e. errors in the DRL files). You have to check for errors by yourself before using a Knowledge Base. The KnowledgeBuilder class has a hasErrors() method and a getResults() methods that you can use to check for errors. If you are using a KieContainer, then you have a verify() method you can use. How are you loading your DRL into the KieBase?
Hope it helps,