接触过Drools的同学都会被复杂的Api给难住，简直就是入门到放弃的一个过程，而EasyRule就是Drools的简化版，裁剪了部分使用场景非常少的复杂功能，也简化了很多Drools中的组件，这样我们在使用EasyRule的时候对于API理解就非常容易了
什么是Easy Rules？ Easy Rules是一个简单的JAVA开源规则引擎，它提供了规则抽象，用于创建包含条件评估和操作执行的规则。 规则引擎API运行一组规则来评估条件和执行操作。
特征轻量级类库中易于学习的基于APIPOJO的注释编程模型开发高效抽象，便于定义业务规则，便于在JAVA中应用它们，支持在原始规则中创建复合规则，支持在可支持语言中定义规则的功能组件(例如结构规则(规则)业务规则，如HashMap，包括条件评估和操作执行，如果条件评估结果为true，则执行相应的操作； 规则引擎(Rule Engine )以指定方式运行规则； 规则监听(Rule Listener )监听规则的执行情况； 监听规则引擎(Rule Engine Listener )监听规则引擎的运行情况； 案例定义规则
注释定义规则：
@rule(name='weatherrule '，description=' ifitrainsthentakeanumbrella ' ) publicclassweatherrule ) @ conditionpublionpublicbobrer ' )； }流编程方式定义规则：
ruleweatherrule=newrulebuilder (.name ) weatherrule ).description (ifitrainsthentakeanumbrella ).when ) ) . equals(true ) ).then ) facts-system.out.println )，take an umbrella！ ' ).build (； 在公式中定义规则：
ruleweatherrule=newmvelrule (.name ) weatherrule ).description (ifitrainsthentakeanumbrella ).When () )。 )； yml文件方式定义规则：
name : ' weather rule ' description : ' ifitrainsthentakeanumbrella ' condition 3360 ' rain==true ' actions 3360-' scraions ruleweatherrule=mvelrulefactory.createrulefrom (new file (' weather-rule.yml ' )； 执行规则：
公共类测试{ publicstaticvoidmain (字符串[ ] args )//definefactsfacts=newfacts )； acts.put('rain '，true )； //definerulesruleweatherrule=. rules rules=new rules ()； Rules.Register(Weatherrule )； //firerulesonknownfactsrulesenginerulesengine=newdefaultrulesengine (； RulesEngine.fire(Rules，facts )； }具体场景案例的场景说明：
假设有这样的场景：
一个数字能被5整除时，输出" fizz "； 一个数字能被7整除时，输出" buzz "； 如果一个数字可以同时被5和7整除，则输出" fizzbuzz "； 如果一个数字不满足上述三个条件，则输出该数字本身。 不使用规则引擎的实现：
publicclassfizzbuzzmain { publicstaticvoidmain (string [ ] args ) for ) intI=1；
i <= 100; i++) { if (((i % 5) == 0) && ((i % 7) == 0)) System.out.print("fizzbuzz"); else if ((i % 5) == 0) System.out.print("fizz"); else if ((i % 7) == 0) System.out.print("buzz"); else System.out.print(i); System.out.println(); } System.out.println(); }}使用Easy Rules实现：
1. 引入依赖
<dependency> <groupId>org.jeasy</groupId> <artifactId>easy-rules-core</artifactId> <version>3.2.0</version></dependency> <dependency> <groupId>org.jeasy</groupId> <artifactId>easy-rules-support</artifactId> <version>3.2.0</version></dependency><dependency> <groupId>org.jeasy</groupId> <artifactId>easy-rules-mvel</artifactId> <version>3.2.0</version></dependency>2. 使用注解方式定义规则：
2.1 定义规则：
public class RuleClass { @Rule(priority = 1) public static class FizzRule { @Condition public boolean isFizz(@Fact("number") int number) { return number % 5 == 0; } @Action public void printFizz() { System.out.print("fizz"); } } @Rule(priority = 2) public static class BuzzRule { @Condition public boolean isBuzz(@Fact("number") int number) { return number % 7 == 0; } @Action public void printBuzz() { System.out.print("buzz"); } } public static class FizzBuzzRule extends UnitRuleGroup { public FizzBuzzRule(Object... rules) { for (Object rule : rules) { addRule(rule); } } @Override public int getPriority() { return 0; } } @Rule(priority = 3) public static class NonFizzBuzzRule { @Condition public boolean isNotFizzNorBuzz(@Fact("number") int number) { return number % 5 != 0 || number % 7 != 0; } @Action public void printInput(@Fact("number") int number) { System.out.print(number); } }}2.2 客户端调用：
public class FizzBuzzMainWithRule { public static void main(String[] args) { // create a rules engine RulesEngineParameters parameters = new RulesEngineParameters().skipOnFirstAppliedRule(true); RulesEngine fizzBuzzEngine = new DefaultRulesEngine(parameters); // create rules Rules rules = new Rules(); rules.register(new FizzRule()); rules.register(new BuzzRule()); rules.register(new FizzBuzzRule(new FizzRule(), new BuzzRule())); rules.register(new NonFizzBuzzRule()); // fire rules Facts facts = new Facts(); for (int i = 1; i <= 100; i++) { facts.put("number", i); fizzBuzzEngine.fire(rules, facts); System.out.println(); } }}3. 使用yml文件定义规则：
3.1 定义规则：
---name: "fizz rule"description: "print fizz if the number is multiple of 5"priority: 1condition: "number % 5 == 0"actions:- "System.out.println("fizz")"---name: "buzz rule"description: "print buzz if the number is multiple of 7"priority: 2condition: "number % 7 == 0"actions:- "System.out.println("buzz")"---name: "fizzbuzz rule"description: "print fizzbuzz if the number is multiple of 5 and 7"priority: 0condition: "number % 5 == 0 && number % 7 == 0"actions:- "System.out.println("fizzbuzz")"---name: "non fizzbuzz rule"description: "print the number itself otherwise"priority: 3condition: "number % 5 != 0 || number % 7 != 0"actions:- "System.out.println(number)"3.2 客户端调用：
public class FizzBuzzMainWithYmlRule { public static void main(String[] args) throws FileNotFoundException { // create a rules engine RulesEngineParameters parameters = new RulesEngineParameters().skipOnFirstAppliedRule(true); RulesEngine fizzBuzzEngine = new DefaultRulesEngine(parameters); // create rules String filePath = System.getProperty("user.dir") + "/src/main/resources/easyrules/fizzbuzz/rule.yml"; Rules rules = MVELRuleFactory.createRulesFrom(new FileReader(filePath)); // fire rules Facts facts = new Facts(); for (int i = 1; i <= 100; i++) { facts.put("number", i); fizzBuzzEngine.fire(rules, facts); System.out.println(); } }} 更多事例 Easy Rules官方wiki参考 Easy Rules官方文档