Drool Global Variable Initialization in drl file

Question

 package com.example.drools; 

 global Integer count; // I want to initialize this count variable with some 
                         default value. 

   rule "Initialize"
   when
   then
       count= 1; // Locally it's possible but want it to set globally which can 
                     be use in any other rules just simply by calling it.
       System.out.println("count="+count);
   end

  rule "Drools Introduction"
  when
  then
     System.out.println("count="+count); // Here output is coming null which in 
                                            want some default value set for 
                                            global value.
  end

So Want to Initialize Count variable in drl file only ?

Answer 1

The way you update a global from inside a rule is by using the automagic variable kcontext:

global Integer count;

rule "Initialize"
salience 100
when
then
       kcontext.getKieRuntime().setGlobal("count", 1);
end    

Some notes:

• You should use a high salience in your rule so it gets executed before any other rule that is also using the global.
• This method will not work if you are using the global in the LHS of your rules. If that's the case I would suggest to use a Fact instead of a global.

Hope it helps,