规则引擎概述
规则引擎，全称为业务规则管理系统，英文名为BRMS
就是把业务里经常变动的代码给抽离出来，接收数据输入，解释业务规则，并根据业务规则做出业务决策
主流产品：drools、VisualRules、iLog
drools
概述
drools是一款由JBoss组织提供的基于Java语言开发的开源规则引擎，可以将复杂且多变的业务规则从硬编码中解放出来，以规则脚本的形式存放在文件或特定的存储介质中(例如存放在数据库中)，使得业务规则的变更不需要修改项目代码、重启服务器就可以在线上环境立即生效。
drools官网地址：https://drools.org/
drools源码下载地址：https://github.com/kiegroup/drools
基础使用
创建spring boot工程
引入drools依赖
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>drools</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>3.0.5</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<java.version>17</java.version>
<drools.version>8.41.0.Final</drools.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-core</artifactId>
<version>${drools.version}</version>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-compiler</artifactId>
<version>${drools.version}</version>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-decisiontables</artifactId>
<version>${drools.version}</version>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-mvel</artifactId>
<version>${drools.version}</version>
</dependency>
</dependencies>
</project>
创建drools配置类
@Configuration
public class DroolsConfig {
private static final KieServices kieServices = KieServices.Factory.get();
//制定规则文件的路径
private static final String RULES_CUSTOMER_RULES_DRL = "rules/order.drl";
@Bean
public KieContainer kieContainer() {
//获得Kie容器对象
KieFileSystem kieFileSystem = kieServices.newKieFileSystem();
kieFileSystem.write(ResourceFactory.newClassPathResource(RULES_CUSTOMER_RULES_DRL));
KieBuilder kieBuilder = kieServices.newKieBuilder(kieFileSystem);
kieBuilder.buildAll();
KieModule kieModule = kieBuilder.getKieModule();
KieContainer kieContainer = kieServices.newKieContainer(kieModule.getReleaseId());
return kieContainer;
}
}