Author: Manohar Viswanathan (manohar.viswanathan@gmail.com)

Features

• Easy implementation of Drools
• Rules can be stored in file or in database
• Rules can be dynamically changed without rebuilding or restarting application
• Both java & groovy objects can be passed to Rules Engine. (Note that groovy domain objects must be in a package)

Installation

First create a grails project:  grails create-app XXX
make XXX the current directory
(if you need an http proxy issue:  grails set-proxy)
grails install-plugin drools
grails run-app

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

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