简介

Drools 是用 Java 语言编写的开放源码规则引擎，使用 Rete 算法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。

详细可见开源业务规则引擎：

Drools中文网

一、项目目录结构

二、集成drools

1、引入依赖


        <!--drools规则引擎-->
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-core</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-compiler</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-templates</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.kie</groupId>
            <artifactId>kie-api</artifactId>
            <version>7.59.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.kie</groupId>
            <artifactId>kie-spring</artifactId>
            <version>7.59.0.Final</version>
        </dependency>

2、新建规则文件

rule1.drl

package com.leopard.drools
import com.leopard.drools.pojo.QueryParam
import com.leopard.drools.service.RuleEngineService

dialect  "java"

rule "boy"
    when queryParam : QueryParam(paramId != null && paramSign.equals("+"))
    then
        RuleEngineService ruleEngineService = new RuleEngineService();
        ruleEngineService.executeAddRule(queryParam);
        System.out.println("参数:getParamId="+queryParam.getParamId()+";getParamSign="+queryParam.getParamSign());
end

rule2.drl

package com.leopard.drools
import com.leopard.drools.pojo.QueryParam

dialect  "java"
rule "girl"
    when queryParam : QueryParam(paramId != null && paramSign.equals("-"))
    then
        System.out.println(queryParam.getParamId() +  "是女孩");
end

3、创建KieUtils（因要做热加载，需要重载规则文件，规则引擎容器要支持变动）

public class KieUtils {

    private static KieContainer kieContainer;

    private static KieSession kieSession;

    private static KModuleBeanFactoryPostProcessor kModuleBeanFactoryPostProcessor;

    public static KieContainer getKieContainer() {
        return kieContainer;
    }

    public static void setKieContainer(KieContainer kieContainer) {
        KieUtils.kieContainer = kieContainer;
        kieSession = kieContainer.newKieSession();
    }

    public static KieSession getKieSession() {
        return kieSession;
    }

    public static void setKieSession(KieSession kieSession) {
        KieUtils.kieSession = kieSession;
    }

    public static KieServices getKieServices() {
        return KieServices.Factory.get();
    }

    public static KModuleBeanFactoryPostProcessor getkModuleBeanFactoryPostProcessor() {
        return kModuleBeanFactoryPostProcessor;
    }

    public static void setkModuleBeanFactoryPostProcessor(KModuleBeanFactoryPostProcessor kModuleBeanFactoryPostProcessor) {
        KieUtils.kModuleBeanFactoryPostProcessor = kModuleBeanFactoryPostProcessor;
    }
}

4、添加初始化配置


@Slf4j
@Configuration
public class RuleEngineConfig {

    public static final String RULES_PATH = "droolsRule/";
    public static final String BASE_RULES_PATH = "classpath*:";

    private final KieServices kieServices = KieServices.Factory.get();

    /**
     * @return
     * @throws IOException
     * @ConditionalOnMissingBean，它是修饰bean的一个注解， 主要实现的是，当你的bean被注册之后，如果而注册相同类型的bean，就不会成功，
     * 它会保证你的bean只有一个，即你的实例只有一个，当你注册多个相同的bean时，会出现异常
     */
    @Bean
    @ConditionalOnMissingBean(KieFileSystem.class)
    public KieFileSystem kieFileSystem() throws IOException {
        KieFileSystem kieFileSystem = kieServices.newKieFileSystem();
        //获取初始化规则文件所在路径
        ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
        Resource[] files = resourcePatternResolver.getResources(BASE_RULES_PATH + RULES_PATH + "*.*");
        String path = null;
        for (Resource file : files) {
            path = RULES_PATH + file.getFilename();
            log.info("path=" + path);
            //将规则文件写规则引擎系统内
            kieFileSystem.write(ResourceFactory.newClassPathResource(path, "UTF-8"));
        }
        return kieFileSystem;
    }

    /**
     * 创建KIE内部容器
     *
     * @return
     * @throws IOException
     */
    @Bean
    @ConditionalOnMissingBean(KieContainer.class)
    public KieContainer kieContainer() throws IOException {

        final KieRepository kieRepository = kieServices.getRepository();
        kieRepository.addKieModule(kieRepository::getDefaultReleaseId);
        KieBuilder kieBuilder = kieServices.newKieBuilder(kieFileSystem());
        kieBuilder.buildAll();
        KieContainer kieContainer = kieServices.newKieContainer(kieRepository.getDefaultReleaseId());
        KieUtils.setKieContainer(kieContainer);
        return kieServices.newKieContainer(kieRepository.getDefaultReleaseId());
    }

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

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

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

5、重载实现，可通过链接数据库刷新规则

@Slf4j
@Service
public class ReloadDroolsRules {

    @Autowired
    private KieSession kieSession;

    @Autowired
    private KieContainer kieContainer;

    /**
     * 重新加载规则
     * @param drlName   规则名称
     * @throws Exception
     */
    public void reload(String drlName) throws Exception {

        KieFileSystem kfs = KieUtils.getKieServices().newKieFileSystem();
//        loadDBRules(drlName, kfs);
        loadFileRules(drlName, kfs);
        KieBuilder kieBuilder = KieUtils.getKieServices().newKieBuilder(kfs).buildAll();
        Results results = kieBuilder.getResults();
        if (results.hasMessages(Message.Level.ERROR)) {
            System.out.println(results.getMessages());
            throw new IllegalStateException("### errors ###");
        }
        KieContainer kieContainer = KieUtils.getKieServices().newKieContainer(KieUtils.getKieServices().getRepository().getDefaultReleaseId());
        KieUtils.setKieContainer(kieContainer);
        System.out.println("新规则重载成功");
    }

    /**
     * 重新读取数据库配置内容
     * @param drlName
     * @param kfs
     * @throws IOException
     */
    private void loadDBRules(String drlName, KieFileSystem kfs) throws IOException {
        //        String path = "src/main/resources/rules/address.drl";
        String path = "src/main/resources/" + RuleEngineConfig.RULES_PATH + "/" + drlName + ".drl";
        // 从数据库加载的规则
        kfs.write(path, "package plausibcheck.adress\n\n import com.leopard.drools.pojo.QueryParam;\n\n rule \"Postcode 6 numbers\"\n\n    when\n  then\n        System.out.println(\"打印日志：更新rules成功!\");\n end");
    }

    /**
     * 重新配置文件
     * @param drlName
     * @param kfs
     * @throws IOException
     */
    private void loadFileRules(String drlName, KieFileSystem kfs) throws IOException {
        // 从classess/rules加载的规则
        //获取初始化规则文件所在路径
        String path = null;
        for (Resource file : getRuleFiles(drlName)) {
            path = RuleEngineConfig.RULES_PATH + file.getFilename();
            log.info("path=" + path);
            //将规则文件写规则引擎系统内
            kfs.write(ResourceFactory.newClassPathResource(path, "UTF-8"));
        }
    }

    private Resource[] getRuleFiles(String drlName) throws IOException {
        if (StringUtils.isEmpty(drlName)) {
            ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
            return resourcePatternResolver.getResources(RuleEngineConfig.BASE_RULES_PATH + RuleEngineConfig.RULES_PATH + "**/*.*");
        }
        ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
        return resourcePatternResolver.getResources(RuleEngineConfig.BASE_RULES_PATH + RuleEngineConfig.RULES_PATH + "**/" + drlName + ".*");
    }
}

三、验证测试

1、创建测试实体类

@Data
public class QueryParam {

    private String paramId;

    private String paramSign;
}

2、添加规则实现

@Slf4j
@Service
public class RuleEngineService {

    /**
     * 插入规则
     *
     * @param param
     */
    public void executeAddRule(QueryParam param) {
        log.info("参数数据:" + param.getParamId() + ";" + param.getParamSign());
        log.info("插入规则");
    }

    /**
     * 移除规则
     *
     * @param param
     */
    public void executeRemoveRule(QueryParam param) {
        log.info("参数数据:" + param.getParamId() + ";" + param.getParamSign());
        log.info("移除规则");
    }
}

3、API调用实现

@RestController
@RequestMapping(value = "test")
public class TestController {

    @Autowired
    private RuleEngineService ruleEngineService;

    @Autowired
    private ReloadDroolsRules reloadDroolsRules;

    @RequestMapping("/param")
    public void param (){
        QueryParam queryParam1 = new QueryParam() ;
        queryParam1.setParamId("1");
        queryParam1.setParamSign("+");
        QueryParam queryParam2 = new QueryParam() ;
        queryParam2.setParamId("2");
        queryParam2.setParamSign("-");
        QueryParam queryParam3 = new QueryParam() ;
        queryParam3.setParamId("3");
        queryParam3.setParamSign("-");
        // 入参
        KieUtils.getKieSession().insert(queryParam2) ;
        KieUtils.getKieSession().insert(queryParam3) ;
        KieUtils.getKieSession().insert(queryParam1) ;
        KieUtils.getKieSession().insert(this.ruleEngineService) ;
        // 返参
        KieUtils.getKieSession().fireAllRules() ;
    }

    @RequestMapping("/reload")
    public String reload (String ruleName) throws Exception {
        // 返参
        reloadDroolsRules.reload(ruleName);
        return "新规则重载成功";
    }

}

运行服务，查看结果

调用

localhost:9666/api/v1/test/param

修改规则文件，调用重新加载配置

localhost:9666/api/v1/test/reload

，不指定配置规则文件名，默认重新加载全部规则，然后重新调用请求

需要注意点：

修改规则配置，是修改加载后的文件，也就是运行项目时，生成的

target目录

下加载的规则文件，而

不是

项目本身resources

下的。

参考文献：

半小时搞定，规则引擎Drools 集成 springboot 热加载

SpringBoot2 整合 Drools规则引擎，实现高效的业务规则

原文链接：https://blog.csdn.net/u014799292/article/details/120195263

简介