Spring Boot集成简易规则引擎 easy-rules

合理的使用规则引擎可以极大的减少代码复杂度，提升代码可维护性。业界知名的开源规则引擎有Drools，功能丰富，但也比较庞大。在一些简单的场景中，我们只需要简易的规则引擎就能满足要求。

本文介绍一个小巧的规则引擎 easy-rules，作为一个lib库提供，支持spring的SPEL表达式，可以很好的集成在spring项目中。

具体的代码参照 示例项目 https://github.com/qihaiyan/springcamp/tree/master/spring-easy-rule

一、概述

通过将业务规则配置的配置文件中，可以精简代码，同时已于维护，当规则修改时，只需要修改配置文件即可。easy-rules是一个小巧的规则引擎，支持spring的SPEL表达式，同时还支持 Apache JEXL 表达式和 MVL 表达式。

二、项目中加入依赖

在项目的gradle中增加依赖关系。

build.gradle:

plugins {id 'org.springframework.boot' version '3.0.5'id 'io.spring.dependency-management' version '1.1.0'id 'java'
}group = 'cn.springcamp'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'configurations {compileOnly {extendsFrom annotationProcessor}testCompileOnly {extendsFrom testAnnotationProcessor}
}repositories {mavenCentral()
}dependencies {implementation "org.springframework.boot:spring-boot-starter-json"implementation 'org.springframework.boot:spring-boot-starter-validation'implementation 'org.jeasy:easy-rules-core:4.1.0'implementation 'org.jeasy:easy-rules-spel:4.1.0'implementation 'org.jeasy:easy-rules-support:4.1.0'annotationProcessor 'org.projectlombok:lombok'testAnnotationProcessor 'org.projectlombok:lombok'testImplementation "org.springframework.boot:spring-boot-starter-test"testImplementation 'org.junit.vintage:junit-vintage-engine'testImplementation 'org.junit.vintage:junit-vintage-engine'
}dependencyManagement {imports {mavenBom "org.springframework.cloud:spring-cloud-dependencies:2022.0.1"}
}test {useJUnitPlatform()
}

三、配置文件

示例程序将业务规则放到配置文件中，业务规则配置文件(demo-rule.yml)代码:

name: "age rule"
description: ""
priority: 1
condition: "#person.getAdult() == false"
actions:- "T(java.lang.System).out.println(\\"Shop: Sorry, you are not allowed to buy alcohol\\")"- "#person.setAdult(true)"- "#person.setAge(18)"
---
name: "alcohol rule"
description: ""
priority: 1
condition: "#person.getAdult() == true"
actions:- "T(java.lang.System).out.println(\\"Shop: you are now allowed to buy alcohol\\")"

配置文件中的规则通过 condition 进行配置，当满足规则时，会调用 actions 中配置的动作。
示例项目使用了spring的SPEL表达式进行规则配置，配置文件中配置了2个规则，第一个规则通过 person这个spring bean中的getAdult()判断是否满足规则，满足规则时调用三个方法。

在spring-boot本身的配置文件中 application.yml 配置规则文件：

rule:skip-on-first-failed-rule: trueskip-on-first-applied-rule: falseskip-on-first-non-triggered-rule: truerules:- rule-id: "demo"rule-file-location: "classpath:demo-rule.yml"

四、代码中对规则引擎进行配置

通过 RuleEngineConfig这个spring的配置类对规则引擎进行配置：

@Slf4j
@EnableConfigurationProperties(RuleEngineConfigProperties.class)
@Configuration
public class RuleEngineConfig implements BeanFactoryAware {@Autowired(required = false)private List<RuleListener> ruleListeners;@Autowired(required = false)private List<RulesEngineListener> rulesEngineListeners;private BeanFactory beanFactory;@Beanpublic RulesEngineParameters rulesEngineParameters(RuleEngineConfigProperties properties) {RulesEngineParameters parameters = new RulesEngineParameters();parameters.setSkipOnFirstAppliedRule(properties.isSkipOnFirstAppliedRule());parameters.setSkipOnFirstFailedRule(properties.isSkipOnFirstFailedRule());parameters.setSkipOnFirstNonTriggeredRule(properties.isSkipOnFirstNonTriggeredRule());return parameters;}@Beanpublic RulesEngine rulesEngine(RulesEngineParameters rulesEngineParameters) {DefaultRulesEngine rulesEngine = new DefaultRulesEngine(rulesEngineParameters);if (!CollectionUtils.isEmpty(ruleListeners)) {rulesEngine.registerRuleListeners(ruleListeners);}if (!CollectionUtils.isEmpty(rulesEngineListeners)) {rulesEngine.registerRulesEngineListeners(rulesEngineListeners);}return rulesEngine;}@Beanpublic BeanResolver beanResolver() {return new BeanFactoryResolver(beanFactory);}@Beanpublic RuleEngineTemplate ruleEngineTemplate(RuleEngineConfigProperties properties, RulesEngine rulesEngine) {RuleEngineTemplate ruleEngineTemplate = new RuleEngineTemplate();ruleEngineTemplate.setBeanResolver(beanResolver());ruleEngineTemplate.setProperties(properties);ruleEngineTemplate.setRulesEngine(rulesEngine);return ruleEngineTemplate;}@Beanpublic RuleListener defaultRuleListener() {return new RuleListener() {@Overridepublic boolean beforeEvaluate(Rule rule, Facts facts) {return true;}@Overridepublic void afterEvaluate(Rule rule, Facts facts, boolean b) {log.info("-----------------afterEvaluate-----------------");log.info(rule.getName() + rule.getDescription() + facts.toString());}@Overridepublic void beforeExecute(Rule rule, Facts facts) {log.info("-----------------beforeExecute-----------------");log.info(rule.getName() + rule.getDescription() + facts.toString());}@Overridepublic void onSuccess(Rule rule, Facts facts) {log.info("-----------------onSuccess-----------------");log.info(rule.getName() + rule.getDescription() + facts.toString());}@Overridepublic void onFailure(Rule rule, Facts facts, Exception e) {log.info("-----------------onFailure-----------------");log.info(rule.getName() + "----------" + rule.getDescription() + facts.toString() + e.toString());}};}@Overridepublic void setBeanFactory(BeanFactory beanFactory) throws BeansException {this.beanFactory = beanFactory;}
}

配置文件中配置了 ruleEngineTemplate这个spring bean，通过ruleEngineTemplate触发规则引擎的执行。

五、执行规则引擎

ruleEngineTemplate配置好后，我们可以在业务代码中执行规则引擎，处理配置文件中配置的业务规则：

最为演示，我们将规则引擎的执行代码放到了 Application 的 run 方法中，程序启动后立即执行规则引擎：

@SpringBootApplication
public class Application implements CommandLineRunner {@AutowiredRuleEngineTemplate ruleEngineTemplate;public static void main(String[] args) {SpringApplication.run(Application.class, args);}@Overridepublic void run(String... args) {Person person = new Person();Facts facts = new Facts();facts.put("person", person);ruleEngineTemplate.fire("demo", facts);}
}

程序执行后可以看到控制台里打印了 Shop: Sorry, you are not allowed to buy alcohol，这个内容对应的是我们在规则文件中的actions中配置的 "T(java.lang.System).out.println(\\"Shop: Sorry, you are not allowed to buy alcohol\\")"，说明规则成功执行了。