V2AS问路
easy-rule 学习
阅读原文时间：2023年07月12日阅读：1

Easyrule是个规则引擎，类似于drools，我们来熟悉一下这个东西

  • [ ] 一个简单实例规则，这个规则会被一直触发，然后行为是打印helloWorld

    @Rule(name="helloWorld",description = "总是打印helloWorld")
    public class HelloWorldRule {
    @Condition
    public boolean when(){
    return true;
    }

    @Action  
public void then(){  
    System.out.println("hello world");  
}

    }

    public class DemoLauncher {
    public static void main(String[] args) {
    Facts facts=new Facts();
    //规则集合定义并注册
    Rules rules=new Rules();
    rules.register(new HelloWorldRule());

        //创建一个规则引擎，并驱动rules  
    RulesEngine rulesEngine=new DefaultRulesEngine();  
            //执行  
    rulesEngine.fire(rules,facts);  
}

    }　

    日志打印：

  • hello world

  • 配上日志包，观察下框架的日志

    [main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Engine parameters { skipOnFirstAppliedRule = false, skipOnFirstNonTriggeredRule = false, skipOnFirstFailedRule = false, priorityThreshold = 2147483647 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Registered rules:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = 'helloWorld', description = '总是打印helloWorld', priority = '2147483646'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Known facts:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rules evaluation started
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule 'helloWorld' triggered
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule 'helloWorld' performed successfully
hello world


org.slf4j.simpleLogger.defaultLogLevel=debug

  • [ ] FizzBuzz : 数字从一到100 当能被5整除的时候发出fizz，被7整除时候发出buzz,同时被5和7整除就发出fizzbuzz

  • [ ] shop：这个示例展示MVEL表达式在EasyRules中的应用，这里示例我们实现一个功能： 小商店卖酒，不能卖给未成年人（法定年龄小于18岁的人）

    • 定义一个人的对象

      @Data
      public class Person {
      private String name;

      private int age;

private boolean adult;

      }

    • MVEL 表达式来写一个规则，这个规则做两件事，首先判断人是不是18岁以上，如果是我们将人的adult属性修改为true,成年人。买酒的行为判断人是否成年如果未成年则拒绝。

      Rule ageRule=new MVELRule()
                .name("年龄规则")
                .description("检查用户年龄是否大于18岁")
                .priority(1)
                .when("person.age > 18")
                .then("person.setAdult(true);");

    • 另外一个规则，是否可以买酒，这次用一个另外的方式来配置规则，写yml文件的方式代码如下：

      name: "alcohol rule"
description: "小孩子不能喝酒"
priority: 2
condition: "person.isAdult()==false"
# 这里是actions数组类型-容易写成action
actions:
  - "System.out.println(\\"Shop: Sorry, you are not allowed to buy alcohol\\");"

    • 运行：用MVELRuleFactory加载规则

      public class MvelRuleDemo {
    public static void main(String[] args) throws Exception {
        Rule ageRule=new MVELRule()
                .name("年龄规则")
                .description("检查用户年龄是否大于18岁")
                .priority(1)
                .when("person.age > 18")
                .then("person.setAdult(true);");
        //定义工厂类
        MVELRuleFactory ruleFactory = new MVELRuleFactory(new YamlRuleDefinitionReader());
        URL url = MvelRuleDemo.class.getClassLoader().getResource("rule/alcohol-rule.yml");
        Rule alcoholRule = ruleFactory.createRule(new FileReader(url.getPath()));
          // 规则合集
    Rules rules=new Rules();
    rules.register(ageRule);
    rules.register(alcoholRule);
      //规则引擎
RulesEngine rulesEngine=new DefaultRulesEngine();
// 实例
System.out.println("来判断接下来的客人能不能买酒");
Person p=new Person();
p.setAge(17);
p.setName("小李");

Facts facts=new Facts();
facts.put("person",p);

// 执行
rulesEngine.fire(rules,facts);
      }
      }


来判断接下来的客人能不能买酒
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Engine parameters { skipOnFirstAppliedRule = false, skipOnFirstNonTriggeredRule = false, skipOnFirstFailedRule = false, priorityThreshold = 2147483647 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Registered rules:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = '年龄规则', description = '检查用户年龄是否大于18岁', priority = '1'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = 'alcohol rule', description = '小孩子不能喝酒', priority = '2'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Known facts:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Fact { person : Person(name=小李, age=17, adult=false) }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rules evaluation started
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '年龄规则' has been evaluated to false, it has not been executed
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule 'alcohol rule' triggered
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule 'alcohol rule' performed successfully
Shop: Sorry, you are not allowed to buy alcohol

    • 修改为19岁后执行-执行完打印一下用户信息，发现用户的成年状态被修改了

      来判断接下来的客人能不能买酒
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Engine parameters { skipOnFirstAppliedRule = false, skipOnFirstNonTriggeredRule = false, skipOnFirstFailedRule = false, priorityThreshold = 2147483647 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Registered rules:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = '年龄规则', description = '检查用户年龄是否大于18岁', priority = '1'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = 'alcohol rule', description = '小孩子不能喝酒', priority = '2'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Known facts:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Fact { person : Person(name=小李, age=19, adult=false) }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rules evaluation started
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '年龄规则' triggered
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '年龄规则' performed successfully
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule 'alcohol rule' has been evaluated to false, it has not been executed
Person(name=小李, age=19, adult=true)

    • [ ] InferenceRulesEngine 持续对已知事实应用规则，直到不再应用规则为止，上面的例子们引擎由默认改为这个的话，代码停不下来，可以试一下，源码也可以读一下处理方式由很大不同。


      • default


        @Override
        
    public void fire(Rules rules, Facts facts) {
        
        triggerListenersBeforeRules(rules, facts);
        
        doFire(rules, facts);
        
        triggerListenersAfterRules(rules, facts);
        
    }
        

        void doFire(Rules rules, Facts facts) {
    if (rules.isEmpty()) {
        LOGGER.warn("No rules registered! Nothing to apply");
        return;
    }
    logEngineParameters();
    log(rules);
    log(facts);
    LOGGER.debug("Rules evaluation started");
    for (Rule rule : rules) {
        final String name = rule.getName();
        final int priority = rule.getPriority();
        if (priority > parameters.getPriorityThreshold()) {
            LOGGER.debug("Rule priority threshold ({}) exceeded at rule '{}' with priority={}, next rules will be skipped",
                    parameters.getPriorityThreshold(), name, priority);
            break;
        }
        if (!shouldBeEvaluated(rule, facts)) {
            LOGGER.debug("Rule '{}' has been skipped before being evaluated",
                name);
            continue;
        }
        if (rule.evaluate(facts)) {
            LOGGER.debug("Rule '{}' triggered", name);
            triggerListenersAfterEvaluate(rule, facts, true);
            try {
                triggerListenersBeforeExecute(rule, facts);
                rule.execute(facts);
                LOGGER.debug("Rule '{}' performed successfully", name);
                triggerListenersOnSuccess(rule, facts);
                if (parameters.isSkipOnFirstAppliedRule()) {
                    LOGGER.debug("Next rules will be skipped since parameter skipOnFirstAppliedRule is set");
                    break;
                }
            } catch (Exception exception) {
                LOGGER.error("Rule '" + name + "' performed with error", exception);
                triggerListenersOnFailure(rule, exception, facts);
                if (parameters.isSkipOnFirstFailedRule()) {
                    LOGGER.debug("Next rules will be skipped since parameter skipOnFirstFailedRule is set");
                    break;
                }
            }
        } else {
            LOGGER.debug("Rule '{}' has been evaluated to false, it has not been executed", name);
            triggerListenersAfterEvaluate(rule, facts, false);
            if (parameters.isSkipOnFirstNonTriggeredRule()) {
                LOGGER.debug("Next rules will be skipped since parameter skipOnFirstNonTriggeredRule is set");
                break;
            }
        }
    }
}</code></pre></li>
        

      • inferenceRulesEngine： 只是在默认的执行外包装了以下一下代码

        

        @Override
        
    public void fire(Rules rules, Facts facts) {
        
        Set<Rule> selectedRules;
        
        do {
        
            LOGGER.debug("Selecting candidate rules based on the following facts: {}", facts);
        
            selectedRules = selectCandidates(rules, facts);
        
            if(!selectedRules.isEmpty()) {
        
                                // 这个delegate就是上面默认的规则引擎
        
                delegate.fire(new Rules(selectedRules), facts);
        
            } else {
        
                LOGGER.debug("No candidate rules found for facts: {}", facts);
        
            }
        
        } while (!selectedRules.isEmpty());
        
    }
        

        private Set&lt;Rule&gt; selectCandidates(Rules rules, Facts facts) {
    Set&lt;Rule&gt; candidates = new TreeSet&lt;&gt;();
    for (Rule rule : rules) {
        if (rule.evaluate(facts)) {
            candidates.add(rule);
        }
    }
    return candidates;
}</code></pre></li></ul>
        

        示例展示一个空调系统，当温度过高时不断降温操作直至温度降低到合适的度数，
        

          

        • 创建一个条件类，来决定什么时候是热
          

          public class HighTemperatureConditon implements org.jeasy.rules.api.Condition {
    // 中文意思评估评定-
    @Override
    public boolean evaluate(Facts facts) {
        Integer temperature=facts.get("temperature");
              return temperature&gt;25;
}

static HighTemperatureConditon itIsHot(){
    return new HighTemperatureConditon();
}
          }
          • 

        • action类，满足条件后的执行内容
          

          public class DecreaseTemperactureAction implements org.jeasy.rules.api.Action {
    @Override
    public void execute(Facts facts) throws Exception {
        System.out.println("温度过高-降温");
        Integer temperature=facts.get("temperature");
        facts.put("temperature",temperature-1);
    }
    static DecreaseTemperactureAction decreaseTemperacture(){
        return new DecreaseTemperactureAction();
    }
}
          • 

        • 执行类-我们注册规则指定规则的触发条件为温度过高，rule.evaluate 方法，然后then执行的结果是：action.execute
          

          public class AirLauncherDemo {
    public static void main(String[] args) {
        Facts facts=new Facts();
        facts.put("temperature",30);
              // 规则
    Rule airRule=  new RuleBuilder()
            .name("空调测试")
            .when(HighTemperatureConditon.itIsHot())
            .then(DecreaseTemperactureAction.decreaseTemperacture())
            .build();
          Rules rules=new Rules();
rules.register(airRule);

//inference引擎，持续不断的执行
RulesEngine rulesEngine=new InferenceRulesEngine();

rulesEngine.fire(rules,facts);
System.out.println(facts.get("temperature").toString());
          }
          }
          • 

        • 日志-我们发现一直降温到25度
          

          [main] DEBUG org.jeasy.rules.core.InferenceRulesEngine - Selecting candidate rules based on the following facts: [ { temperature : 30 } ]
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Engine parameters { skipOnFirstAppliedRule = false, skipOnFirstNonTriggeredRule = false, skipOnFirstFailedRule = false, priorityThreshold = 2147483647 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Registered rules:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = '空调测试', description = 'description', priority = '2147483646'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Known facts:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Fact { temperature : 30 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rules evaluation started
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' triggered
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' performed successfully
[main] DEBUG org.jeasy.rules.core.InferenceRulesEngine - Selecting candidate rules based on the following facts: [ { temperature : 29 } ]
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Engine parameters { skipOnFirstAppliedRule = false, skipOnFirstNonTriggeredRule = false, skipOnFirstFailedRule = false, priorityThreshold = 2147483647 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Registered rules:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = '空调测试', description = 'description', priority = '2147483646'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Known facts:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Fact { temperature : 29 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rules evaluation started
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' triggered
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' performed successfully
[main] DEBUG org.jeasy.rules.core.InferenceRulesEngine - Selecting candidate rules based on the following facts: [ { temperature : 28 } ]
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Engine parameters { skipOnFirstAppliedRule = false, skipOnFirstNonTriggeredRule = false, skipOnFirstFailedRule = false, priorityThreshold = 2147483647 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Registered rules:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = '空调测试', description = 'description', priority = '2147483646'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Known facts:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Fact { temperature : 28 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rules evaluation started
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' triggered
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' performed successfully
[main] DEBUG org.jeasy.rules.core.InferenceRulesEngine - Selecting candidate rules based on the following facts: [ { temperature : 27 } ]
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Engine parameters { skipOnFirstAppliedRule = false, skipOnFirstNonTriggeredRule = false, skipOnFirstFailedRule = false, priorityThreshold = 2147483647 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Registered rules:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = '空调测试', description = 'description', priority = '2147483646'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Known facts:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Fact { temperature : 27 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rules evaluation started
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' triggered
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' performed successfully
[main] DEBUG org.jeasy.rules.core.InferenceRulesEngine - Selecting candidate rules based on the following facts: [ { temperature : 26 } ]
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Engine parameters { skipOnFirstAppliedRule = false, skipOnFirstNonTriggeredRule = false, skipOnFirstFailedRule = false, priorityThreshold = 2147483647 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Registered rules:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule { name = '空调测试', description = 'description', priority = '2147483646'}
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Known facts:
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Fact { temperature : 26 }
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rules evaluation started
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' triggered
[main] DEBUG org.jeasy.rules.core.DefaultRulesEngine - Rule '空调测试' performed successfully
[main] DEBUG org.jeasy.rules.core.InferenceRulesEngine - Selecting candidate rules based on the following facts: [ { temperature : 25 } ]
[main] DEBUG org.jeasy.rules.core.InferenceRulesEngine - No candidate rules found for facts: [ { temperature : 25 } ]
温度过高-降温
温度过高-降温
温度过高-降温
温度过高-降温
温度过高-降温
25
        

        这个示例说明，InferenceRulesEngine 会不断的重新进行判断执行，所以必须在满足条件执行的操作中修改自身实例。不然会崩溃

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