8.6. Packaging

A package is a collection of rules and other related constructs, such as imports and globals. The package members are typically related to each other, such as HR rules. A package represents a namespace, which ideally is kept unique for a given grouping of rules. The package name itself is the namespace, and is not related to files or folders in any way.
It is possible to assemble rules from multiple rule sources, and have one top level package configuration that all the rules are kept under (when the rules are assembled). It is not possible to merge into the same package resources declared under different names. A single Rulebase may, however, contain multiple packages built on it. A common structure is to have all the rules for a package in the same file as the package declaration (so that is it entirely self-contained).

8.6.1. Import Statements

Import statements work like import statements in Java. You need to specify the fully qualified paths and type names for any objects you want to use in the rules. BRMS automatically imports classes from the Java package of the same name, and also from the package java.lang.

8.6.2. Using Globals

In order to use globals you must:
  1. Declare the global variable in the rules file and use it in rules. Example: 
    global java.util.List myGlobalList;

rule "Using a global"
when
    eval( true )
then
    myGlobalList.add( "Hello World" );
end
  2. Set the global value on the working memory. It is best practice to set all global values before asserting any fact to the working memory. Example: 
    List list = new ArrayList();
WorkingMemory wm = rulebase.newStatefulSession();
wm.setGlobal( "myGlobalList", list );

8.6.3. The From Element

The from element allows you to pass a Hibernate session as a global. It also lets you pull data from a named Hibernate query.

8.6.4. Using Globals with an e-Mail Service

Procedure 8.1. Task

  1. Open the integration code that is calling the rule engine.
  2. Obtain your emailService object and then set it in the working memory.
  3. In the DRL, declare that you have a global of type emailService and give it the name "email".
  4. In your rule consequences, you can use things like email.sendSMS(number, message).

    Warning

    Globals are not designed to share data between rules and they should never be used for that purpose. Rules always reason and react to the working memory state, so if you want to pass data from rule to rule, assert the data as facts into the working memory.

    Important

    Do not set or change a global value from inside the rules. We recommend to you always set the value from your application using the working memory interface.