规则引擎----easy rules

一、规则引擎的作用

将复杂的if else判断剥离出来

二、使用

2.1、引入POM

		<!--easy rules核心库-->
        <dependency>
            <groupId>org.jeasy</groupId>
            <artifactId>easy-rules-core</artifactId>
            <version>3.3.0</version>
        </dependency>

        <!--规则定义文件格式，支持json,yaml等-->
        <dependency>
            <groupId>org.jeasy</groupId>
            <artifactId>easy-rules-support</artifactId>
            <version>3.3.0</version>
        </dependency>

        <!--支持mvel规则语法库-->
        <dependency>
            <groupId>org.jeasy</groupId>
            <artifactId>easy-rules-mvel</artifactId>
            <version>3.3.0</version>

2.2、编写规则

2.2.1、注解

package com.xx.rule.number;

import org.jeasy.rules.annotation.Action;
import org.jeasy.rules.annotation.Condition;
import org.jeasy.rules.annotation.Fact;
import org.jeasy.rules.annotation.Rule;

/**
 * @author aqi
 * @date 2023/5/6 16:03
 */
@Rule(name = "被3整除", description = "number如果被3整除，打印：number is 3", priority = 1)
public class ThreeRule {

    /**
     * Condition:条件判断注解：如果return true， 执行Action
     */
    @Condition
    public boolean isThree(@Fact("number") int number) {
        return number % 3 == 0;
    }

    /**
     * Action 执行方法注解
     */
    @Action
    public void threeAction(@Fact("number") int number) {
        System.out.println(number + ":可以被3整除");
    }
}

2.2.2、表达式

MVELRule ageRule = new MVELRule()
                .name("age rule")
                .description("判断这个人是否成年,是否可以饮酒")
                .priority(1)
                .when("person.age > 18").then("person.setAdult(true);");

2.2.3 yml配置文件

name: "alcohol rule"
description: "children are not allowed to buy alcohol"
priority: 2
condition: "person.isAdult() == false"
actions:
  - "System.out.println(\"你还未满18岁!\");"

2.2.4 组合规则

UnitRuleGroup myUnitRuleGroup = new UnitRuleGroup("myUnitRuleGroup", "组合规则");
        myUnitRuleGroup.addRule(ageRule);
        myUnitRuleGroup.addRule(alcoholRule);

2.2.5 组合规则说明

类	说明
UnitRuleGroup	要么应用所有规则，要么不应用任何规则（AND逻辑）
ActivationRuleGroup	它触发第一个适用规则，并忽略组中的其他规则（XOR逻辑）
ConditionalRuleGroup	如果具有最高优先级的规则计算结果为true，则触发其余规则

2.2.6 字段说明

字段	说明
name	规则名称
description	规则描述
priority	规则执行顺序，越小越先执行
condition	条件
actions	满足条件之后的执行动作

2.3、规则使用

2.3.1、注解规则使用

package com.xx;

import com.xx.rule.number.ThreeRule;
import org.jeasy.rules.api.Facts;
import org.jeasy.rules.api.Rules;
import org.jeasy.rules.api.RulesEngine;
import org.jeasy.rules.core.DefaultRulesEngine;

public class Main {
    public static void main(String[] args) {
        // 创建规则执行引擎
        RulesEngine rulesEngine = new DefaultRulesEngine();
        // 创建规则
        Rules rules = new Rules();
        rules.register(new ThreeRule());
        // 设置参数
        Facts facts = new Facts();
        for (int i = 1; i <= 50; i++) {
            //规则因素，对应的name，要和规则里面的@Fact 一致
            facts.put("number", i);
            //执行规则
            rulesEngine.fire(rules, facts);
            System.out.println();
        }
    }
}

2.3.2、表达式和yml规则使用

package com.xx;

import com.xx.domain.Person;
import org.jeasy.rules.api.Facts;
import org.jeasy.rules.api.Rule;
import org.jeasy.rules.api.Rules;
import org.jeasy.rules.api.RulesEngine;
import org.jeasy.rules.core.DefaultRulesEngine;
import org.jeasy.rules.core.RuleBuilder;
import org.jeasy.rules.mvel.MVELRuleFactory;
import org.jeasy.rules.support.YamlRuleDefinitionReader;
import org.springframework.util.ResourceUtils;

import java.io.FileReader;

/**
 * 基于MVEL表达式实现规则引擎
 * @author aqi
 */
public class ShopMain {
    public static void main(String[] args) throws Exception {
        Person person = new Person();
        person.setName("tom");
        person.setAge(20);
        Facts facts = new Facts();
        facts.put("person", person);

        // 表达式
        Rule ageRule = new RuleBuilder()
                .name("age rule")
                .description("判断这个人是否成年,是否可以饮酒")
                .when(e -> Integer.parseInt(e.get("person.age")) > 18)
                .then(e -> e.put("person.adult", true))
                .build();


        // yml配置文件
        Rule alcoholRule = new MVELRuleFactory(new YamlRuleDefinitionReader()).
                 createRule(new FileReader(ResourceUtils.getFile("classpath:alcohol-rule.yml")));

        Rules rules = new Rules();
        rules.register(ageRule);
        rules.register(alcoholRule);

        //创建规则执行引擎，并执行规则
        RulesEngine rulesEngine = new DefaultRulesEngine();
        rulesEngine.fire(rules, facts);
        System.out.println(person);

    }
}

2.3.1、规则引擎可配参数

参数	说明
skipOnFirstAppliedRule	当一个规则成功应用时，跳过余下的规则
skipOnFirstFailedRule	当一个规则失败时，跳过余下的规则
skipOnFirstNonTriggeredRule	当一个规则未触发时，跳过余下的规则
rulePriorityThreshold	当优先级超过指定的阈值时，跳过余下的规则

通过如下方式设置

RulesEngineParameters parameters = new RulesEngineParameters().skipOnFirstAppliedRule(true);
        RulesEngine rulesEngine = new DefaultRulesEngine(parameters);