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;
@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
public boolean isThree(@Fact("number") int number) {
return number % 3 == 0;
}
@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) {
RulesEngine rulesEngine = new DefaultRulesEngine();
Rules rules = new Rules();
rules.register(new ThreeRule());
Facts facts = new Facts();
for (int i = 1; i <= 50; i++) {
facts.put("number", i);
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;
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);
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();
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);
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);