How to import Java static method into Drools file?

Question

The java class and static method code is:

public class DroolsStringUtils {
    public static boolean isEmpty(String param) {
        if (param == null || "".equals(param)) {
            return true;
        }
        return false;
    }
}

The drl code is:

package com.rules

import com.secbro.drools.utils.DroolsStringUtils.isEmpty;

rule CheckIsEmpty
  when
    isEmpty("");
  then
    System.out.println("the param is not empty");
  end

But the IDEA hints:

"cannot relove" on the method 'isEmpty("")'.

I just want to import a static method from java class to drl file.

Answer 1

Use import static to import a static method.

import  static  com.secbro.drools.utils.DroolsStringUtils.isEmpty;
//      ^^^^^^

(edited:) and of course you cannot call a static method where a pattern is required:

rule CheckIsEmpty
when
    eval( isEmpty("") )
then
    System.out.println("the param is not empty");
end

(It helps considerably to read the Drools documentation.)