Mano’s Tech World

I have just released a Grails Plugin for Drools. The plugin details can also be found at http://www.grails.org/Drools+Plugin.

Drools is a business rule management system (BRMS) and an enhanced Rules Engine implementation, ReteOO, based on Charles Forgy’s Rete algorithm tailored for the Java language.

Features

• Easy implementation of Drools
• Rules can be stored in file or in database
• Rules can be dynamically changed without rebuilding or restarting application

Installation

grails install-plugin drools

Usage

• Install the plugin
• Verify example rules:
  http://localhost:8080/your_app/drools/example
• Create your own rules: http://localhost:8080/your_app/drools and use droolsService in your code

Components

• DroolsController: Provides CRUD functionality for Drools Rule
• DroolsService: Fires all rules

DroolsService
droolsService.fireRules(resource, ruleKey, objList)

• resource: specifies where the rules are stored. ‘file’ or ‘db’
• ruleKey: identifier for the rule. For ‘file’ resource, this would be the name of the file (eg:ticket_example.drl). For ‘db’ resource, this is the Drools Rule key
• objList: list of objects that need to be put in session

Example

A simple Ticket processing system is available in the plugin. This example shows how tickets are processed based on their subscription plan.

Run the example: http://localhost:8080/your_app/drools/example

Your console output should be:

Start processing Ticket # 3
Start processing Ticket # 2
Start processing Ticket # 1
Firing rule Bronze Priority for Ticket # 3
Firing rule Silver Priority for Ticket # 2
Firing rule Gold Priority for Ticket # 1
Firing rule Special Discount for Ticket # 1

Display on your browser should be:

Tickets due for processing:
Ticket #1: Customer[Name:Jack, Subscription:Gold, Discount:0%] Status[New]
Ticket #2: Customer[Name:Tom, Subscription:Silver, Discount:0%] Status[New]
Ticket #3: Customer[Name:Bill, Subscription:Bronze, Discount:0%] Status[New]
Firing rules now ...
Tickets after processing:
Ticket #1: Customer[Name:Jack, Subscription:Gold, Discount:5%] Status[Escalate]
Ticket #2: Customer[Name:Tom, Subscription:Silver, Discount:0%] Status[Escalate]
Ticket #3: Customer[Name:Bill, Subscription:Bronze, Discount:0%] Status[Pending]