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210 lines
8.6 KiB
Markdown
210 lines
8.6 KiB
Markdown
***
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<div align="center">
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<b><em>Easy Rules</em></b><br>
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The simple, stupid rules engine for Java™
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</div>
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<div align="center">
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[](http://opensource.org/licenses/MIT)
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[](https://coveralls.io/github/j-easy/easy-rules?branch=master)
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[](https://github.com/j-easy/easy-rules/actions)
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[](http://search.maven.org/#artifactdetails|org.jeasy|easy-rules-core|3.4.0|)
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[](http://www.javadoc.io/doc/org.jeasy/easy-rules-core)
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[](https://gitter.im/j-easy/easy-rules)
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</div>
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***
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## Latest news
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* 08/12/2019: Version 3.4.0 is out with a few enhancements and bug fixes. Checkout the release notes [here](https://github.com/j-easy/easy-rules/releases).
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* 25/04/2019: Version 3.3.0 is out with JSON and SpEL support! Checkout what's new [here](https://github.com/j-easy/easy-rules/releases).
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* 09/04/2018: Version 3.2.0 is out with new features and bug fixes. Checkout what's new [here](https://github.com/j-easy/easy-rules/releases).
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## What is Easy Rules?
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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:
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> 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.
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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.
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## Core features
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* Lightweight library and easy to learn API
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* POJO based development with annotation programming model
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* Useful abstractions to define business rules and apply them easily with Java
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* The ability to create composite rules from primitive ones
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* The ability to define rules using an Expression Language (Like MVEL and SpEL)
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## Example
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### 1. First, define your rule..
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#### Either in a declarative way using annotations:
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```java
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@Rule(name = "weather rule", description = "if it rains then take an umbrella" )
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public class WeatherRule {
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@Condition
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public boolean itRains(@Fact("rain") boolean rain) {
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return rain;
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}
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@Action
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public void takeAnUmbrella() {
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System.out.println("It rains, take an umbrella!");
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}
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}
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```
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#### Or in a programmatic way with a fluent API:
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```java
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Rule weatherRule = new RuleBuilder()
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.name("weather rule")
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.description("if it rains then take an umbrella")
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.when(facts -> facts.get("rain").equals(true))
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.then(facts -> System.out.println("It rains, take an umbrella!"))
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.build();
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```
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#### Or using an Expression Language:
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```java
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Rule weatherRule = new MVELRule()
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.name("weather rule")
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.description("if it rains then take an umbrella")
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.when("rain == true")
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.then("System.out.println(\"It rains, take an umbrella!\");");
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```
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#### Or using a rule descriptor:
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Like in the following `weather-rule.yml` example file:
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```yaml
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name: "weather rule"
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description: "if it rains then take an umbrella"
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condition: "rain == true"
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actions:
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- "System.out.println(\"It rains, take an umbrella!\");"
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```
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```java
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MVELRuleFactory ruleFactory = new MVELRuleFactory(new YamlRuleDefinitionReader());
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Rule weatherRule = ruleFactory.createRule(new FileReader("weather-rule.yml"));
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```
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### 2. Then, fire it!
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```java
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public class Test {
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public static void main(String[] args) {
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// define facts
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Facts facts = new Facts();
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facts.put("rain", true);
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// define rules
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Rule weatherRule = ...
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Rules rules = new Rules();
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rules.register(weatherRule);
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// fire rules on known facts
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RulesEngine rulesEngine = new DefaultRulesEngine();
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rulesEngine.fire(rules, facts);
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}
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}
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```
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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.
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## Contribution
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You are welcome to contribute to the project with pull requests on GitHub.
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If you found a bug or want to request a feature, please use the [issue tracker](https://github.com/j-easy/easy-rules/issues).
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For any further question, you can use the [Gitter](https://gitter.im/j-easy/easy-rules) channel of the project.
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## Awesome contributors
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* [andersonkyle](https://github.com/andersonkyle)
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* [beccagaspard](https://github.com/beccagaspard)
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* [bpoussin](https://github.com/bpoussin)
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* [cgonul](https://github.com/cgonul)
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* [cemo](https://github.com/cemo)
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* [dagframstad](https://github.com/dagframstad)
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* [danrivcap](https://github.com/danrivcap)
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* [drem-darios](https://github.com/drem-darios)
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* [gs-spadmanabhan](https://github.com/gs-spadmanabhan)
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* [JurMarky](https://github.com/JurMarky)
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* [jordanjennings](https://github.com/jordanjennings)
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* [kayeight](https://github.com/kayeight)
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* [khandelwalankit](https://github.com/khandelwalankit)
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* [lranasingha](https://github.com/lranasingha)
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* [mrcritical](https://github.com/mrcritical)
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* [paulbrejla](https://github.com/paulbrejla)
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* [richdouglasevans](https://github.com/richdouglasevans)
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* [ruanjiehui](https://github.com/ruanjiehui)
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* [spearway](https://github.com/spearway)
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* [toudidel](https://github.com/toudidel)
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* [vinoct6](https://github.com/vinoct6)
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* [wg1j](https://github.com/wg1j)
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* [will-gilbert](https://github.com/will-gilbert)
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* [WayneCui](https://github.com/WayneCui)
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* [sanmibuh](https://github.com/sanmibuh)
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* [shivmitra](https://github.com/shivmitra)
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* [zhhaojie](https://github.com/zhhaojie)
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Thank you all for your contributions!
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## Easy Rules in other languages
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* [EasyRulesGo](https://github.com/CrowdStrike/easyrulesgo) : A port of EasyRules to Golang by [@jiminoc](https://github.com/jiminoc)
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* [EasyRulesGroovy](https://github.com/will-gilbert/easyrules-tutorials-groovy) : A port of EasyRules tutorials to Groovy by [@will-gilbert](https://github.com/will-gilbert)
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* [EasyRulesCsharp](https://github.com/feldrim/EasyRulesCsharp) : A port of EasyRules to CSharp (WIP) by [@feldrim](https://github.com/feldrim)
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## Who is using Easy Rules?
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* [Apache Nifi](https://nifi.apache.org) (see [Nifi EasyRules Bundle](https://github.com/apache/nifi/tree/master/nifi-nar-bundles/nifi-easyrules-bundle))
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* [Open Remote](https://openremote.io) (see [build.gradle](https://github.com/openremote/openremote/blob/master/model/build.gradle#L27))
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* [Open Smart Register Platform](http://smartregister.org) (see [build.gradle](https://github.com/OpenSRP/opensrp-client-anc/blob/master/opensrp-anc/build.gradle#L205))
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## Credits
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Many thanks to [YourKit, LLC](https://www.yourkit.com/) for providing a free license of [YourKit Java Profiler](https://www.yourkit.com/java/profiler/index.jsp) to support the development of Easy Rules.
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## License
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Easy Rules is released under the terms of the MIT license:
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```
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The MIT License (MIT)
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Copyright (c) 2020 Mahmoud Ben Hassine (mahmoud.benhassine@icloud.com)
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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```
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