Drools - 规则引擎快速体验

十毛

发布于 2019-03-27 15:15:24

1.7K0

发布于 2019-03-27 15:15:24

Drools 是用 Java 语言编写的开放源码规则引擎，使用 Rete 算法（参阅参考资料）对所编写的规则求值。Drools 允许使用声明方式表达业务逻辑。可以使用非 XML 的本地语言编写规则，从而便于学习和理解。并且，还可以将 Java 代码直接嵌入到规则文件中，这令 Drools 的学习更加吸引人

Hello World

pom.xml

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.kie</groupId>
        <artifactId>kie-ci</artifactId>
        <version>7.17.0.Final</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

Application

@SpringBootApplication
public class DroolsApplication {
    public static void main(String[] args) {
        SpringApplication.run(DroolsApplication.class, args);
    }
    @Bean
    public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
        return args -> {
            System.out.println("start to run task");
            KieServices kieServices = KieServices.Factory.get();
            KieContainer kieContainer = kieServices.newKieClasspathContainer();

            KieSession kieSession = kieContainer.newKieSession("hello-rules");
            kieSession.fireAllRules();
            kieSession.destroy();
        };
    }
}

kmodule.xml设置 resources/META-INF/kmodule.xml

<?xml version="1.0" encoding="UTF-8"?>
<kmodule xmlns="http://www.drools.org/xsd/kmodule">
    <kbase name="rules" packages="rules">
        <ksession name="hello-rules"/>
    </kbase>
</kmodule>

注意hello-rules与Application代码中的一致

规则文件 resources/rules/test.drl

package rules;

rule "test"
  when
  then
    System.out.println("Hello World!");
end

注意这里的目录rules要与kmodule.xml中的package="rules"保持一致

执行Application（标准的Spring Boot项目启动）

Demo

实体类(Person.java)

@Data
@AllArgsConstructor
public class Person {
    private String name;
    private Integer age;
    private Boolean gender;
}

Application(DroolsApplication.java)

@Bean
public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
    return args -> {
        System.out.println("start to run task");
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kieContainer = kieServices.newKieClasspathContainer();

        Person tenmao = new Person("tenmao", 20, true);
        Person bill = new Person("bill", 17, false);

        KieSession kieSession = kieContainer.newKieSession("hello-rules");
        kieSession.insert(tenmao);
        kieSession.insert(bill);
        kieSession.fireAllRules();
        kieSession.destroy();
    };
}

规则(test.drl)

package rules;
import com.tenmao.drools.Person

rule "test"
  when
  #过滤年龄大于18岁的
    $p: Person(age > 18)
  then
  #输出
    System.out.println($p);
end