how to fire selected rules in Drool

Question

1- Is it possible to fire only selected rules for a particular customer in Drool. Suppose I have 100 rules these are rules from different customers. So when a particular customer opens up the application I want to fire only those rules which belong to him. It can be possible that a rule can belong to more than one customer.

2 - I want to get a list of rules which needed to be fired for a particular customer and a list of facts to fire those rules so that I can fetch only that particular facts from my db. And after fetching them, fire those rules which are specific to that customer

Answer 1

You'll have to identify the owning customers along with the rules, or maintain data associating a customer with rules. I think that the latter is to be preferred, but I'll outline both solutions. In any case, the Customer has to be identified by a fact.

rule "some rule"
when
    Customer( id in ("Smith&Co", "Brown&Sons", "Jones Inc." ) )
    ...
then ... end

To associcate a Customer with rules you need:

class Customer {
    private String name;
    private List<String> rules;
    //...
}

and write an AgendaFilter

class RuleFilter implements AgendaFilter {
    static List<Customer> customers = new ArrayList<>();
    static {
        customers.add(...);
        ...
    }
    static RuleFilter getFilterFor( String custname ){
         for( Customer cust: customers ){
             if( cust.getName().equals( custname ) ){
                 return cust;
             }
         }
         throw IllegalArgumentException( "no customer: " + custname );
    }
    Customer current;
    RuleFilter( Customer current ){
        this.current = current;
    }
    // ... getters & setters
    boolean accept( Match match ){
        return current.getRules().contains( match.getRule().getName() );
    }
}

And run the session for a customer by providing a filter instance:

 AgendaFilter currFilter = RuleFilter( getFilterFor( customername ) ); 
 fireAllRules( currFilter );