如何从 DMN model（Drools Business Central）调用 static Java 方法

Question

I am using Business Central version 7.40.0. When calling static Java method std from Drools Business Central DMN project/model, I'm getting following error:

DMN: Error compiling Java function 'stdev' on node 'stdev': Error resolving external function as defined by: function(val) external { java: { class: ""com.sample.StandardDeviation"", method signature: ""std(java.lang.Number)"" }}...
Error compiling the referenced FEEL expression

I have:

1. Created Maven jar with static Java method

package com.sample;

import java.math.BigDecimal;
    
public class StandardDeviation {
    
    public static BigDecimal std(Number val) {  
        return new BigDecimal(val.doubleValue() * 2);
    }
}

2. Imported Jar as Artifacts to Drools Business Central ,

3. Added Dependency to DMN project

4. In my DMN model, I am calling static Java method inside 'stdev' BKM (business knowledge model) element. BKM with class and method signature

   • class: "com.sample.StandardDeviation"
   • method signature: "std(java.lang.Number)"

5. Saving BKM/DMN or building the model gives above error

What could be the issue? Am I doing anything incorrectly? How to check the logs in Drools Business Central?

Answer 1

We are aware of this issue as it was reported at DROOLS-5577

Workaround exists as discussed in separate forum and as detailed in the JIRA issue, which was later confirmed by OP as in:

1. Ignore this validation error (red popup) while Saving the DMN Model with the editor
2. Proceed to Deploy the KJAR BC Project as usual