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:
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Drools 6.2.0.Final
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Grails versions 2.3.11, 2.4.5, and 2.5.0
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OSX 10.10.4
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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.
If you are upgrading from version 0.9.x, there are some breaking changes you will have to address.
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
The plugin offers a variety of ways to use rules. The RuleTests and TestController classes show several examples.
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)
}
}
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])
}
}
Edit your BuildConfig.groovy:
plugins {
// other plugins
compile ":drools:1.1.1"
}
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.
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"
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"
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.
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"
See DroolsConfig.groovy for configuration options and instructions. Drools Spring Integration provides more information.
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.
The plugin offers three command-line scripts.
Running grails create-drools-config will copy the default DroolsConfig.groovy to your application's grails-app/conf directory.
Running grails create-drools-context will copy the default drools-context.xml to your application's grails-app/conf directory.
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"