Drools

Last updated
Drools
Original authors Bob McWhirte, Mark Proctor
Developer The Apache Software Foundation
Initial releaseAugust 1, 2005;20 years ago (2005-08-01)
Stable release
10.1.0 / July 8, 2025;4 months ago (2025-07-08) [1]
Repository github.com/apache/incubator-kie-drools
Written in Java
Operating system Cross-platform
Type Rules engine, Decision management
License ASL 2
Website kie.apache.org

Drools is a business rule management system (BRMS) with a forward and backward chaining inference-based rules engine, more correctly known as a production rule system, using an enhanced implementation of the Rete algorithm.

Contents

Drools supports the Java Rules Engine API (Java Specification Request 94) standard for its business rule engine and enterprise framework for the construction, maintenance, and enforcement of business policies in an organization, application, or service.

Drools in Apache Kie

Drools, as part of the Kie Community [2] has entered Apache Incubator in January, 2023. [3]

Red Hat Decision Manager

Red Hat Decision Manager (formerly Red Hat JBoss BRMS [4] ) is a business rule management system and reasoning engine for business policy and rules development, access, and change management. [5] JBoss Enterprise BRMS is a productized version of Drools with enterprise-level support available. JBoss Rules is also a productized version of Drools, but JBoss Enterprise BRMS is the flagship product. [6]

Components of the enterprise version: [7]

Drools and Guvnor are JBoss Community open source projects. As they are mature, they are brought into the enterprise-ready product JBoss Enterprise BRMS.

Components of the JBoss Community version: [10]

Example

This example [11] illustrates a simple rule to print out information about a holiday in July. It checks a condition on an instance of the Holiday class, and executes Java code if that condition is true.

rule"validate holiday"when$h1 : Holiday( month == "july" ) thenSystem.out.println($h1.name + ":" + $h1.month); end

The purpose of dialect "mvel" is to point the getter and setters of the variables of your Plain Old Java Object (POJO) classes. Consider the above example, in which a Holiday class is used and inside the circular brackets (parentheses) "month" is used. So with the help of dialect "mvel" the getter and setters of the variable "month" can be accessed.

Dialect "java" is used to help us write our Java code in our rules. There is one restriction or characteristic on this. We cannot use Java code inside the "when" part of the rule but we can use Java code in the "then" part.

We can also declare a Reference variable $h1 without the $ symbol. There is no restriction on this. The main purpose of putting the $ symbol before the variable is to mark the difference between variables of POJO classes and Rules.

See also

References

  1. ↑ "Drools - Releases" . Retrieved 2025-04-11.
  2. ↑ "KIE Community". Archived from the original on 2024-01-17.
  3. ↑ "KIE Status". Archived from the original on 2023-12-25.
  4. ↑ "JBoss Enterprise BRMS". Red Hat.
  5. ↑ "JBoss Enterprise BRMS". Red Hat.
  6. ↑ "JBoss Enterprise BRMS: Answers to frequently asked questions" (PDF). JBoss Community.
  7. ↑ "JBoss Enterprise BRMS Platform 5.1". Red Hat. Archived from the original on 2011-03-18.
  8. ↑ "JBoss Enterprise BRMS datasheet" (PDF). Red Hat. p. 4.
  9. ↑ "Drools - Business Rules Management System (Java™, Open Source)".
  10. ↑ "Drools 5 - The Business Logic integration Platform". JBoss Community.
  11. ↑ http://downloads.jboss.com/drools/docs/5.1.1.34858.FINAL/drools-expert/html_single/index.html#d0e2676%5B%5D
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