orit1992 opened a new issue, #6243:
URL: https://github.com/apache/incubator-kie-drools/issues/6243
I've encountered an issue in Drools **8.44.0.Final** where rule execution
changes **depending on whether a subclass overrides a getter from its
superclass**. Even more concerning, in some cases, **a property that is
actually non-null gets evaluated as null in WHEN condition**.
I was able to verify that the issue occurs for sure in Drools versions from
**7.74.1** up to **10.0.0** (latest available version) using both Java11 and
Java17, the version **6.5.0.Final** doesn't have the issue.
**Steps to Reproduce**
Consider the following examples rules:
``` drl
rule "Set Address"
salience 1
when
$fact : Person( address == null)
then
System.out.println("Person Hash " + $fact.hashCode());
modify($fact) {
setAddress("ROME")
}
end
rule "Set worker name"
when
$fact : Worker(
$address: address != null
)
then
System.out.println("Worker Hash " + $fact.hashCode());
System.out.println("(address != null) evaluated and address is " +
$address );
modify($fact) {
setName("PIPPO")
}
end
```
And the following Java classes:
``` java
public class Person {
private String name;
private int age;
private String address;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
public class Worker extends Person {
// If this override is removed, the rule "Set worker name" works fine.
@Override
public String getAddress() {
return super.getAddress();
}
}
public class Student extends Person {}
```
**Unexpected Behavior**
- If `Worker` **does NOT override** `getAddress()`, the rule `"Set worker
name"` **executes**, and `name` is set to "PIPPO".
- If `Worker` **overrides** `getAddress()`, the rule `"Set worker name"`
**is never triggered**.
- The only difference between the two scenarios is the overridden method in
Worker, which should not affect rule execution logic.
**Even More Concerning**: **Evaluation of** `null` **When the Value is
Non-Null**
To illustrate a more severe case, consider the following additional rule:
``` drl
/**
* When Worker class overrides getAddress(), then `address == null`
evaluates to true,
* but it will print a non-null value.
* Uncomment the following rule and comment the previous ones to test.
*/
rule "Check worker address"
when
$fact : Worker( $address: address == null )
then
System.out.println("Worker Hash " + $fact.hashCode());
System.out.println("(address == null) evaluated but address is " +
$address);
modify($fact) {
setName("PIPPO");
}
end
```
With this setup:
- Drools evaluates `address == null` as `true`, even when `getAddress()`
actually returns a **non-null** value.
- The rule fires, but the printed value of $address is unexpectedly **not
null**.
---
To help reproduce this issue, I've created a
[repo](https://github.com/orit1992/droolsbehavior/tree/main) containing Maven
project (Java17) with unit tests that demonstrate the behavior:
**Student** class: extends Person and **Does not override** `getAddress()`,
and the rule execution works as expected
(`com.example.DroolsRuleTest#testStudentSessionAddress`).
**Worker** class: extends Person and **Overrides** `getAddress()`, causing
the rule execution to **fail**
(`com.example.DroolsRuleTest#testWorkerSessionAddress`).
Thanks for your time
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