17.12. Using Stateful and Stateless RuleSessions

Procedure 17.3. Task

1. Get the runtime by accessing the RuleServiceProvider as shown:

   RuleRuntime ruleRuntime = ruleServiceProvider.getRuleRuntime();

2. To create a rule session, use one of the two RuleRuntime public constants. These are "RuleRuntime.STATEFUL_SESSION_TYPE" and "RuleRuntime.STATELESS_SESSION_TYPE", accompanying the URI to the RuleExecutionSet you wish to instantiate a RuleSession for.
3. Optionally, access the properties to specify globals.
4. The createRuleSession(...) method will return a RuleSession instance. You should cast it to StatefulRuleSession or StatelessRuleSession:

   (StatefulRuleSession) session =
     ruleRuntime.createRuleSession( uri,
                                    null,
                                    RuleRuntime.STATEFUL_SESSION_TYPE );
   session.addObject( new PurchaseOrder( "cheese" ) );
   session.executeRules();

5. When using a StatelessRuleSession, you can only call executeRules(List list) passing a list of objects, and an optional filter, the resulting objects are then returned:

   (StatelessRuleSession) session =
     ruleRuntime.createRuleSession( uri,
                                    null,
                                    RuleRuntime.STATELESS_SESSION_TYPE );
   List list = new ArrayList();
   list.add( new PurchaseOrder( "even more cheese" ) );
   
   List results = new ArrayList();
   results = session.executeRules( list );