Drools规则引擎入门

Drools规则引擎入门

Drools（JBoss Rules ）具有一个易于访问企业策略、易于调整以及易于管理的开源业务规则引擎，符合业内标准，速度快、效率高。业务分析师或审核人员可以利用它轻松查看业务规则，从而检验是否已编码的规则执行了所需的业务规则。

Drools 5.x版本代码（淘汰）

pom.xml文件，内容：引入单元测试、drools、slf4j包

    <properties>
        <drools-version>7.0.0.Finaldrools-version>
    properties>
    <dependencies>
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.12version>
        dependency>
        <dependency>
            <groupId>org.droolsgroupId>
            <artifactId>drools-compilerartifactId>
            <version>${drools-version}version>
        dependency>
        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-log4j12artifactId>
            <version>1.7.21version>
        dependency>
    dependencies>

com.mylitboy.drools.model.Product.java文件，内容：类型及折扣

/** 产品类 */
public class Product {

    // 钻石
    public static final String DIAMOND = "0";
    // 黄金
    public static final String GOLD = "1";

    // 类别
    private String type;
    // 折扣
    private int discount;

    // Getter/Setter
}

resources/com/rules/Rules.drl文件，内容为相关规则内容。

package com.rules

import com.mylitboy.drools.model.Product

rule Offer4Diamond
    when
        productObject : Product(type==Product.DIAMOND)
    then
        productObject.setDiscount(15);
     end

rule Offer4Gold
    when
        productObject : Product(type==Product.GOLD)
    then
        productObject.setDiscount(30);
     end

Test.java文件，用于单元测试规则引擎。

@Test
public void oldExecuteDrools() {
    
    KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
    // 添加规则文件。
    kbuilder.add(ResourceFactory.newClassPathResource("com/rules/Rules.drl", this.getClass()), ResourceType.DRL);
    // 校验规则是否有问题。
    if (kbuilder.hasErrors()) {
        System.out.println(kbuilder.getErrors().toArray());
    }

    // 获取规则中的包
    Collection<KnowledgePackage> pkgs = kbuilder.getKnowledgePackages();
    // 添加规则中的包到规则base
    KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
    // 将KnowledgePackage 集合添加到KnowledgeBase中
    kbase.addKnowledgePackages(pkgs);

    // 获取KnowledgeSession
    StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();

    Product product = new Product();
    product.setType(Product.GOLD);
    
    // 引入匹配请求
    ksession.insert(product);
    // 匹配所有规则
    ksession.fireAllRules();
    // 销毁
    ksession.dispose();

    System.out.println("The discount for the product " + product.getType() + " is " + product.getDiscount() + "%");
}

运行单元测试，结果如下：

The discount for the product 1 is 30%

Drools 7.x版本代码

com.mylitboy.drools.model.Product.java文件，内容：类型及折扣，参考Drools 5.x版本代码
resources/com/rules/Rules.drl文件，内容为相关规则内容，参考Drools 5.x版本代码

pom.xml文件，引入kie-spring、kie-api、drools-compiler包：

<dependency>
    <groupId>org.kiegroupId>
    <artifactId>kie-springartifactId>
    <version>7.9.0.Finalversion>
    <exclusions>
        <exclusion>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-txartifactId>
        exclusion>
        <exclusion>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-beansartifactId>
        exclusion>
        <exclusion>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-coreartifactId>
        exclusion>
        <exclusion>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-contextartifactId>
        exclusion>
    exclusions>
dependency>
<dependency>
    <groupId>org.droolsgroupId>
    <artifactId>drools-compilerartifactId>
    <version>7.9.0.Finalversion>
dependency>
<dependency>
    <groupId>org.kiegroupId>
    <artifactId>kie-apiartifactId>
    <version>RELEASEversion>
    <scope>compilescope>
dependency>

新增文件：
resources/META-INF/kmodule.xml文件

<kmodule xmlns="http://www.drools.org/xsd/kmodule">
    <kbase name="rules" packages="com.rules">
        <ksession name="ksession-rule"/>
    kbase>
kmodule>

单元测试代码：

@Test
public void testRules() {
    // 构建KisServices
    KieServices ks = KieServices.Factory.get();
    // 根据Classpath:MATE-INF目录加载kmodule.xml文件
    KieContainer kieContainer = ks.getKieClasspathContainer();
    // 获取kmodule.xml中配置的名称为ksession-rule的session，默认为有状态的。
    KieSession kSession = kieContainer.newKieSession("ksession-rule");

    Product product = new Product();
    product.setType(Product.GOLD);

    // 添加product FACT对象
    kSession.insert(product);
    // 进行规则判断
    int count = kSession.fireAllRules();
    System.out.println("命中了" + count + "条规则!");
    System.out.println("商品" + product.getType() + "的商品折扣为" + product.getDiscount() + "%");
}

运行单元测试，结果如下：

命中了1条规则!
商品1的商品折扣为30%

Drools集成至SpringBoot

创建SpringBoot项目

com.mylitboy.drools.model.Product.java文件，内容同上。

resources/com/rules/Rules.drl文件，内容同上。

DroolsAutoConfiguration.java文件，内容：

@Configuration
public class DroolsAutoConfiguration {
    private static final String RULES_PATH = "com/rules/";

    @Bean
    @ConditionalOnMissingBean(KieFileSystem.class)
    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();
        return resourcePatternResolver.getResources("classpath*:" + RULES_PATH + "**/*.*");
    }

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

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

    @Bean
    @ConditionalOnMissingBean(KModuleBeanFactoryPostProcessor.class)
    public KModuleBeanFactoryPostProcessor kiePostProcessor() {
        return new KModuleBeanFactoryPostProcessor();
    }

}

单元测试：

@RunWith(SpringRunner.class)
@SpringBootTest
public class DroolsSpringbootApplicationTests {
    @Resource
    private KieSession kieSession;

    @Test
    public void test(){
        Product product = new Product();
        product.setType(Product.GOLD);

        // 添加product FACT对象
        kieSession.insert(product);
        // 进行规则判断
        int count = kieSession.fireAllRules();
        System.out.println("命中了" + count + "条规则!");
        System.out.println("商品" + product.getType() + "的商品折扣为" + product.getDiscount() + "%");
    }
}

单元测试结果：

命中了1条规则!
商品1的商品折扣为30%