The simple, stupid rules engine for Java.zip

*** <div align="center"> <b><em>Easy Rules</em></b><br> The simple, stupid rules engine for Java&trade; </div> <div align="center"> [](http://opensource.org/licenses/MIT) [](https://github.com/j-easy/easy-rules/actions) [](http://search.maven.org/#artifactdetails|org.jeasy|easy-rules-core|4.1.0|) [](http://www.javadoc.io/doc/org.jeasy/easy-rules-core) [](https://img.shields.io/badge/Project%20status-Maintenance-orange.svg) </div> *** ## Project status As of December 2020, Easy Rules is in maintenance mode. This means only bug fixes will be addressed from now on. Version 4.1.x is the only supported version. Please consider upgrading to this version at your earliest convenience. ## Latest news * 06/12/2020: Version 4.1 is out with a new module to support [Apache JEXL](https://commons.apache.org/proper/commons-jexl/) as an additional supported expression language! You can find all details about other changes in the [release notes](https://github.com/j-easy/easy-rules/releases). ## What is Easy Rules? Easy Rules is a Java rules engine inspired by an article called *"[Should I use a Rules Engine?](http://martinfowler.com/bliki/RulesEngine.html)"* of [Martin Fowler](http://martinfowler.com/) in which Martin says: > You can build a simple rules engine yourself. All you need is to create a bunch of objects with conditions and actions, store them in a collection, and run through them to evaluate the conditions and execute the actions. This is exactly what Easy Rules does, it provides the `Rule` abstraction to create rules with conditions and actions, and the `RulesEngine` API that runs through a set of rules to evaluate conditions and execute actions. ## Core features * Lightweight library and easy to learn API * POJO based development with an annotation programming model * Useful abstractions to define business rules and apply them easily with Java * The ability to create composite rules from primitive ones * The ability to define rules using an Expression Language (Like MVEL, SpEL and JEXL) ## Example ### 1. First, define your rule.. #### Either in a declarative way using annotations: ```java @Rule(name = "weather rule", description = "if it rains then take an umbrella") public class WeatherRule { @Condition public boolean itRains(@Fact("rain") boolean rain) { return rain; } @Action public void takeAnUmbrella() { System.out.println("It rains, take an umbrella!"); } } ``` #### Or in a programmatic way with a fluent API: ```java Rule weatherRule = new RuleBuilder() .name("weather rule") .description("if it rains then take an umbrella") .when(facts -> facts.get("rain").equals(true)) .then(facts -> System.out.println("It rains, take an umbrella!")) .build(); ``` #### Or using an Expression Language: ```java Rule weatherRule = new MVELRule() .name("weather rule") .description("if it rains then take an umbrella") .when("rain == true") .then("System.out.println(\"It rains, take an umbrella!\");"); ``` #### Or using a rule descriptor: Like in the following `weather-rule.yml` example file: ```yaml name: "weather rule" description: "if it rains then take an umbrella" condition: "rain == true" actions: - "System.out.println(\"It rains, take an umbrella!\");" ``` ```java MVELRuleFactory ruleFactory = new MVELRuleFactory(new YamlRuleDefinitionReader()); Rule weatherRule = ruleFactory.createRule(new FileReader("weather-rule.yml")); ``` ### 2. Then, fire it! ```java public class Test { public static void main(String[] args) { // define facts Facts facts = new Facts(); facts.put("rain", true); // define rules Rule weatherRule = ... Rules rules = new Rules(); rules.register(weatherRule); // fire rules on known facts RulesEngine rulesEngine = new DefaultRulesEngine(); rulesEngine.fire(rules, facts); } } ``` This is the hello world of Easy Rules. You can find other examples like the [Shop](https://github.com/j-easy/easy-rules/wiki/shop), [Airco](https://github.com/j-easy/easy-rules/wiki/air-conditioning) or [WebApp](https://github.com/j-easy/easy-rules/wiki/web-app) tutorials in the wiki. ## Contribution You are welcome to contribute to the project with pull requests on GitHub. Please note that Easy Rules is in [maintenance mode](https://github.com/j-easy/easy-rules#project-status), which means only pull requests for bug fixes will be considered. If you believe you found a bug or have any question, please use the [issue tracker](https://github.com/j-easy/easy-rules/issues). ## Awesome contributors * [Alexey1Gavrilov](https://github.com/Alexey1Gavrilov) * [andersonkyle](https://github.com/andersonkyle) * [aston2016](https://github.com/aston2016) * [avakimov](https://github.com/avakimov) * [beccagaspard](https://github.com/beccagaspard) * [bpoussin](https://github.com/bpoussin) * [cgonul](https://github.com/cgonul) * [cemo](https://github.com/cemo) * [dagframstad](https://github.com/dagframstad) * [danrivcap](https://github.com/danrivcap) * [Desislav-Petrov](https://github.com/Desislav-Petrov) * [drem-darios](https://github.com/drem-darios) * [gs-spadmanabhan](https://github.com/gs-spadmanabhan) * [JurMarky](https://github.com/JurMarky) * [jordanjennings](https://github.com/jordanjennings) * [kayeight](https://github.com/kayeight) * [khandelwalankit](https://github.com/khandelwalankit) * [lranasingha](https://github.com/lranasingha) * [laurikimmel](https://github.com/laurikimmel) * [mrcritical](https://github.com/mrcritical) * [paulbrejla](https://github.com/paulbrejla) * [richdouglasevans](https://github.com/richdouglasevans) * [ruanjiehui](https://github.com/ruanjiehui) * [spearway](https://github.com/spearway) * [stefanbirkner](https://github.com/stefanbirkner) * [toudidel](https://github.com/toudidel) * [vinoct6](https://github.com/vinoct6) * [wg1j](https://github.com/wg1j) * [will-gilbert](https://github.com/will-gilbert) * [WayneCui](https://github.com/WayneCui) * [sanmibuh](https://github.com/sanmibuh) * [shivmitra](https://github.com/shivmitra) * [zhhaojie](https://github.com/zhhaojie) Thank you all for your contributions! ## Easy Rules in other languages * [EasyRulesGo](https://github.com/CrowdStrike/easyrulesgo) : A port of EasyRules to Golang by [@jiminoc](https://github.com/jiminoc) * [EasyRulesGroovy](https://github.com/will-gilbert/easyrules-tutorials-groovy) : A port of EasyRules tutorials to Groovy by [@will-gilbert](https://github.com/will-gilbert) * [EasyRulesCsharp](https://github.com/feldrim/EasyRulesCsharp) : A port of EasyRules to CSharp (WIP) by [@feldrim](https://github.com/feldrim) ## Who is using Easy Rules? * [Apache Nifi](https://nifi.apache.org) (see [Nifi EasyRules Bundle](https://github.com/apache/nifi/tree/rel/nifi-1.12.1/nifi-nar-bundles/nifi-easyrules-bundle)) * [Open Remote](https://openremote.io) (see [build.gradle](https://github.com/openremote/openremote/blob/v1.0.4/model/build.gradle#L27)) * [Open Smart Register Platform](http://smartregister.org) (see [build.gradle](https://github.com/OpenSRP/opensrp-client-anc/blob/v1.5.0/opensrp-anc/build.gradle#L196)) * [Toad Edge by Quest](https://support.quest.com/fr-fr/technical-documents/toad-edge/2.1/user-guide/14) * [Extreme Networks](https://cloud.kapostcontent.net/pub/c4c24aae-b82d-44e4-8d86-01c235e4b40f/open-source-declaration-for-extr-xmc-8-dot-5) ## Credits ![YourKit Java Profiler](https://www.yourkit.co