Drools规则引擎-Drools入门案例

echo编辑整理，欢迎转载，转载请声明文章来源。欢迎添加echo微信(微信号：t2421499075) 交流学习。

---

Drools的实现并不难，关键是了解他的语法即可

入门案例

• 创建一个简单的SpringBoot项目

• 选择依赖的时候，添加一个web依赖即可

• 在新项目的pom.xml中添加drools的相关依赖

<properties>
    <java.version>1.8</java.version>
    <drools.version>7.14.0.Final</drools.version>
</properties>
<dependencies>
<!-- drools依赖 -->
    <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>
    <!-- 决策表 -->
    <dependency>
        <groupId>org.drools</groupId>
        <artifactId>drools-decisiontables</artifactId>
        <version>${drools.version}</version>
    </dependency>
    <!-- 模板 -->
    <dependency>
        <groupId>org.drools</groupId>
        <artifactId>drools-templates</artifactId>
        <version>${drools.version}</version>
    </dependency>
    
    <dependency>
        <groupId>org.kie</groupId>
        <artifactId>kie-api</artifactId>
        <version>${drools.version}</version>
    </dependency>
</dependencies>

• 创建Kie相关 Bean 使其被spring管理

import org.kie.api.KieBase;
import org.kie.api.KieServices;
import org.kie.api.builder.KieBuilder;
import org.kie.api.builder.KieFileSystem;
import org.kie.api.builder.KieModule;
import org.kie.api.builder.KieRepository;
import org.kie.api.builder.ReleaseId;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;
import org.kie.internal.io.ResourceFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.core.io.Resource;

import java.io.IOException;

/**
 * @author tang.sl
 * @date 2021-01-05 09:37
 */
@Configuration
public class KiaSessionConfig {

    private static final String RULES_PATH = "rules/";

    @Bean
    public KieFileSystem kieFileSystem() throws IOException {
        KieFileSystem kieFileSystem = getKieServices().newKieFileSystem();
        for (Resource file : getRuleFiles()) {
            kieFileSystem.write(ResourceFactory.newClassPathResource(RULES_PATH + file.getFilename(), "UTF-8"));
        }
        return kieFileSystem;
    }

    private Resource[] getRuleFiles() throws IOException {

        ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
        final Resource[] resources = resourcePatternResolver.getResources("classpath*:" + RULES_PATH + "**/*.*");
        return resources;

    }

    @Bean
    public KieContainer kieContainer() throws IOException {

        final KieRepository kieRepository = getKieServices().getRepository();
        kieRepository.addKieModule(new KieModule() {
            public ReleaseId getReleaseId() {
                return kieRepository.getDefaultReleaseId();
            }
        });

        KieBuilder kieBuilder = getKieServices().newKieBuilder(kieFileSystem());
        kieBuilder.buildAll();
        return getKieServices().newKieContainer(kieRepository.getDefaultReleaseId());

    }

    private KieServices getKieServices() {
        return KieServices.Factory.get();
    }

    @Bean
    public KieBase kieBase() throws IOException {
        return kieContainer().getKieBase();
    }

    @Bean
    public KieSession kieSession() throws IOException {
        return kieContainer().newKieSession();
    }
}

到目前为止，我们的基本准备工作就已经完成了，我们可以创建实际的案例来使用Drools了。

• 根据前面的需求定义一个实体类

@Data
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String name;
    private String age;
    private String address;
    private String phone;
    private String sex;
}

• 创建drl规则文件 根据前几篇文章描述的内容，我们来设计一个规则文件。文件放在resources目录下面，在该目录下面创建一个rules统一存放后面所有的rule文件

package com.echo.drools.dto
import com.echo.drools.dto.User
dialect "java"

rule "address eq beijing"
    when
        $user: User(address == "北京")
    then
         System.out.println($user.getName() + "是个北漂");
    end

rule "address eq shanghai"
    when
        $user: User(address == "上海")
    then
         System.out.println($user.getName() + "是个上漂");
    end

• 然后我们就可以来测试使用这个规则

import com.echo.drools.dto.User;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Test;
import org.kie.api.runtime.KieSession;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
class DroolsApplicationTests {

    @Autowired
    private KieSession session;

    @Test
    void contextLoads() {
        User user = new User();
        user.setAddress("北京");
        user.setAge("20");
        user.setName("echo");
        user.setPhone("136123456");
        user.setSex("1");
        // 插入用户
        session.insert(user);
        // 执行规则
        session.fireAllRules();
    }

    /**
     * 记得执行完成之后释放资源
     */
    @AfterEach
    public void runDispose() {
        session.dispose();
    }

}

• 多次测试 结果和我们的符合我们原有的预期，比如上面的实例，最终会在控制台输出“echo是北漂”。

注意：我们这里仅仅写了两个规则，并且也没有写对应的业务代码，这个后面再讲，仅仅只是一个入门展示案例。不要多纠结为什么没有业务代码