This plugin is no longer maintained.

Grails plugin for integrating Drools

Drools is a Business Rules Management System (BRMS) solution. The plugin fully supports Drools kie-spring integration. Use Drools Usage - Google Groups for Drools questions that are not related to the plugin. You might find Drools Setup - Google Groups useful although the plugin should make this unnecessary.

The plugin has been tested using the sample application and test script in the following environment:

• Drools 6.2.0.Final

• Grails versions 2.3.11, 2.4.5, and 2.5.0

• OSX 10.10.4

• JDK 1.8.0_45

If you want to use the plugin with a version of Grails earlier than 2.3.0, see Grails 2.2.5 and Earlier.

If you have a question, problem, suggestion, or want to report a bug, please submit an issue. I will reply as soon as I can.

Release Notes

Breaking Changes

If you are upgrading from version 0.9.x, there are some breaking changes you will have to address.

Drools Components

The plugin uses the following Drools components.

org.kie.api.KieBase: API, Source Interface

org.kie.api.KieServices: API, Source Interface, Source Implementation

org.kie.api.builder.KieBuilder: API, Source Interface, Source Implementation

org.kie.api.builder.KieFileSystem: API, Source Interface, Source Implementation

org.kie.api.runtime.KieSession: API, Source Interface

org.kie.api.runtime.StatelessKieSession: API, Source Interface

org.kie.spring.KModuleBeanFactoryPostProcessor: Source

How the Plugin Works

The plugin offers a variety of ways to use rules. The RuleTests and TestController classes show several examples.

Beans

You can define beans using either a configuration file grails-app/conf/DroolsConfig.groovy or an xml file grails-app/conf/drools-context.xml. This will allow you to do something like this:

class SomeService {
   def packageOneStatelessSession

   def someMethod() {
      def fact1 = SomeDomain.get(123)
      def fact2 = SomeOtherDomain.get(123)
      def facts = [fact1, fact2]
      packageOneStatelessSession.execute(facts)
   }
}

Database and File Rules

The DroolsService offers several methods to use rules stored in a database or on the file system (classpath). For example, assuming you have several rules in the database with a packageName of "ticket", you could do something like this:

class SomeOtherService {
   def droolsService

   def someMethod() {
      def fact1 = SomeDomain.get(123)
      def fact2 = SomeOtherDomain.get(123)
      droolsService.fireFromDatabase("ticket", [fact1, fact2])
   }
}

Plugin Installation and Configuration

Installation

Edit your BuildConfig.groovy:

plugins {
   // other plugins
   compile ":drools:1.1.1"
}

Configuration

Although Grails prefers convention over configuration, you cannot avoid some configuration for the Drools beans.

After the plugin is installed you will find a heavily commented DroolsConfig.groovy in grails-app/conf/ that you can use as a starting point for configuring your beans. When your application is compiled this file is parsed and grails-app/conf/drools-context.xml is created (or overwritten). For example, DroolsTestConfig.groovy is the one used for plugin integration tests.

BuildConfig.groovy

There are two options that you can configure in your grails-app/conf/BuildConfig.groovy. The defaults are shown below:

grails.plugin.drools.configurationType = "droolsConfigGroovy"
grails.plugin.drools.drlFileLocation = "rules"

grails.plugin.drools.configurationType

The option below will stop the plugin from overwriting grails-app/conf/drools-context.xml. This will allow you to edit the file manually without losing changes.

grails.plugin.drools.configurationType = "droolsContextXml"

grails.plugin.drools.drlFileLocation

This option is the directory root for Rule files, those files with a "drl" or "rule" suffix. Note the lack of leading and trailing slashes below:

grails.plugin.drools.drlFileLocation = "drools-rules"

You can take advantage of rule packages by creating subdirectories under drlFileLocation. See the plugin's src/resources/rules for an example.

All files in this directory and its subdirectories with a "drl" or "rule" suffix will be copied to the classpath.

Config.groovy

If you change the domain class used to store your rules without using the script create-drools-domain, you will have to edit the corresponding configuration option in your grails-app/conf/Config.groovy.

grails.plugin.drools.droolsRuleDomainClass = "com.example.DroolsRule"

DroolsConfig.groovy

See DroolsConfig.groovy for configuration options and instructions. Drools Spring Integration provides more information.

Using the Plugin

Drools Rule Files

Changes to rule files will be reloaded in development mode if you start the application with:

grails -reloading run-app

Changing the grails.plugin.drools.drlFileLocation option could affect the packages property for a KieBase. For example, for the option

grails.plugin.drools.drlFileLocation = "drools-rules"

with a rule file located in a subdirectory:

~/my-grails-app/src/resources/drools-rules/packageOne/ruleFile1.drl

The rule file will be available on the classpath as

drools-rules/packageOne/ruleFile1.drl

and the KieBase packages property would be:

packages: "drools-rules.packageOne"

The Rule Language Reference in the Drools documentation describes the syntax for the rules files.

Scripts

The plugin offers three command-line scripts.

create-drools-config

Running grails create-drools-config will copy the default DroolsConfig.groovy to your application's grails-app/conf directory.

create-drools-context

Running grails create-drools-context will copy the default drools-context.xml to your application's grails-app/conf directory.

create-drools-domain

Running grails create-drools-config will create a domain class with a package and name of your choice. Use this class to store your rules in the database.

It will also add or update the configuration option below in your application's grails-app/conf/Config.groovy:

grails.plugin.drools.droolsRuleDomainClass = "com.example.DroolsRule"