在《Drools7.0.0.Final规则引擎教程》之Springboot集成中介绍了怎样将Drools与Springboot进行集成，本篇博客介绍一下集成之后，如何实现从数据库读取规则并重新加载规则的简单demo。因本章重点介绍的是Drools相关操作的API，所以将查询数据库部分的操作省略，直接使用数据库查询出的规则代码来进行规则的重新加载。另外，此示例采用访问一个http请求来进行重新加载，根据实际需要可考虑定时任务进行加载等扩展方式。最终的使用还是要结合具体业务场景来进行分析扩展。
整体项目结构
上图是基于intellij maven的项目结构。其中涉及到springboot的Drools集成配置类，重新加载规则类。一些实体类和工具类。下面会抽出比较重要的类进行分析说明。
DroolsAutoConfiguration
@Configuration public class DroolsAutoConfiguration { private static final String RULES_PATH = "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(); KieContainer kieContainer = getKieServices().newKieContainer(kieRepository.getDefaultReleaseId()); KieUtils.setKieContainer(kieContainer); 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 { KieSession kieSession = kieContainer().newKieSession(); KieUtils.setKieSession(kieSession); return kieSession; } @Bean @ConditionalOnMissingBean(KModuleBeanFactoryPostProcessor.class) public KModuleBeanFactoryPostProcessor kiePostProcessor() { return new KModuleBeanFactoryPostProcessor(); } }
此类主要用来初始化Drools的配置，其中需要注意的是对KieContainer和KieSession的初始化之后都将其设置到KieUtils类中。
KieUtils
KieUtils类中存储了对应的静态方法和静态属性，供其他使用的地方获取和更新。
public class KieUtils { private static KieContainer kieContainer; private static KieSession kieSession; 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; } }
ReloadDroolsRules
提供了reload规则的方法，也是本篇博客的重点之一，其中从数据库读取的规则代码直接用字符串代替，读者可自行进行替换为数据库操作。
@Service public class ReloadDroolsRules { public void reload() throws UnsupportedEncodingException { KieServices kieServices = KieServices.Factory.get(); KieFileSystem kfs = kieServices.newKieFileSystem(); kfs.write("src/main/resources/rules/temp.drl", loadRules()); KieBuilder kieBuilder = kieServices.newKieBuilder(kfs).buildAll(); Results results = kieBuilder.getResults(); if (results.hasMessages(Message.Level.ERROR)) { System.out.println(results.getMessages()); throw new IllegalStateException("### errors ###"); } KieUtils.setKieContainer(kieServices.newKieContainer(getKieServices().getRepository().getDefaultReleaseId())); System.out.println("新规则重载成功"); } private String loadRules() { // 从数据库加载的规则 return "package plausibcheck.adress\n\n import com.neo.drools.model.Address;\n import com.neo.drools.model.fact.AddressCheckResult;\n\n rule \"Postcode 6 numbers\"\n\n when\n then\n System.out.println(\"规则2中打印日志：校验通过!\");\n end"; } private KieServices getKieServices() { return KieServices.Factory.get(); } }
TestController
提供了验证入口和reload入口。
@RequestMapping("/test") @Controller public class TestController { @Resource private ReloadDroolsRules rules; @ResponseBody @RequestMapping("/address") public void test(){ KieSession kieSession = KieUtils.getKieSession(); Address address = new Address(); address.setPostcode("994251"); AddressCheckResult result = new AddressCheckResult(); kieSession.insert(address); kieSession.insert(result); int ruleFiredCount = kieSession.fireAllRules(); System.out.println("触发了" + ruleFiredCount + "条规则"); if(result.isPostCodeResult()){ System.out.println("规则校验通过"); } } @ResponseBody @RequestMapping("/reload") public String reload() throws IOException { rules.reload(); return "ok"; } }
其他
其他类和文件内容参考springboot集成部分或demo源代码。
操作步骤如下：启动项目访问http://localhost:8080/test/address 会首先触发默认加载的address.drl中的规则。当调用reload之后，再次调用次方法会发现触发的规则已经变成重新加载的规则了。
CSDN demo下载地址：http://download.csdn.net/detail/wo541075754/9918297
GitHub demo下载地址：https://github.com/secbr/drools/tree/master/springboot-drools-reload-rules
