Drools规则引擎(Java)

前言：

Drools是一款基于Java的开源规则引擎
　　实现了将业务决策从应用程序中分离出来。

　　优点：
　　　　1、简化系统架构，优化应用
　　　　2、提高系统的可维护性和维护成本
　　　　3、方便系统的整合
　　　　4、减少编写“硬代码”业务规则的成本和风险

不多说，直接low代码，此例是使用springboot项目为基础：

1.需添加maven依赖 使用7.x：

        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-core</artifactId>
            <version>7.4.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-compiler</artifactId>
            <version>7.4.1.Final</version>
        </dependency>复制代码

2.main方法测试

//执行的主类
public class Application {

    public static void test1() throws Exception {

        KieSession kieSession = check(getRule());

        IrssetDroolsVo  drools = new IrssetDroolsVo();
        drools.setSurpDayCnt(2);
        kieSession.insert(drools);
       int i = kieSession.fireAllRules();
      System.out.println("命中： " + i +"返回结果：" + drools.getMsg());
       
    }


    /**
     * 不进行检查
     * @param rule
     * @return
     */
    public static KieSession getSession(String rule) {
        KieSession kieSession = null;
        try {
            KnowledgeBuilder builder = KnowledgeBuilderFactory.newKnowledgeBuilder();
            builder.add(ResourceFactory.newByteArrayResource(rule.getBytes("UTF-8")),ResourceType.DRL);
            InternalKnowledgeBase knowledgeBase = KnowledgeBaseFactory.newKnowledgeBase();
            Collection<KiePackage> packages = builder.getKnowledgePackages();
            knowledgeBase.addPackages(packages);
            kieSession = knowledgeBase.newKieSession();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return kieSession;
    }

    
    /**
     * 检查
     * @param sq
     * @return
     * @throws Exception
     */
    private static KieSession check(String sq) throws Exception   {
        KieSessionRepo kieSession = new KieSessionRepo();
        KieServices kieServices = KieServices.Factory.get();
        KieFileSystem kfs = kieServices.newKieFileSystem();
  
        kfs.write("src/main/resources/test.drl", sq );
        KieBuilder kieBuilder = kieServices.newKieBuilder(kfs).buildAll();
        Results results = kieBuilder.getResults();
        if (results.hasMessages(Message.Level.ERROR)) {
            for (Message msg : results.getMessages()) {
              System.out.println("drools script error info : " + msg.getText());
            }
            throw  new  Exception("drools script error");
        }

        kieSession.setKieContainer("test", kieServices.newKieContainer(KieServices.Factory.get().getRepository().getDefaultReleaseId()));
         
    return kieSession.getKieSession("test");
}
    
    public static String getRule() {
        StringBuffer ruleSb = new StringBuffer();
        ruleSb.append(" package rule_10001;\n");
        ruleSb.append("import com.learn.rule.model.IrssetDroolsVo\n");
        ruleSb.append("rule rule_10001 \n");
        ruleSb.append("when \n");
        ruleSb.append("$riskDroolsVo : IrssetDroolsVo(surpDayCnt>=2 && surpDayCnt<=10); \n");
        ruleSb.append("then \n");
        ruleSb.append("$riskDroolsVo.setMsg(\"命中了\"); \n");
        ruleSb.append("end");
        
        System.out.println(ruleSb.toString());
        return ruleSb.toString();
    }

    public static void main(String[] args) throws Exception {
        test1();
    }复制代码

3.执行的实体类：

public  class IrssetDroolsVo  implements Serializable {
   
    private Integer surpDayCnt = null;
    private boolean mBlack = false;
    private String msg;


    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
    
    public IrssetDroolsVo() {
    }
    private static final long serialVersionUID = 1L;
    
    
    public Integer getSurpDayCnt() {
        return surpDayCnt;
    }
    public void setSurpDayCnt(Integer surpDayCnt) {
        this.surpDayCnt = surpDayCnt;
    }
    public boolean ismBlack() {
        return mBlack;
    }
    public void setmBlack(boolean mBlack) {
        this.mBlack = mBlack;
    }
 
}复制代码

4. KieSeesionRepo:

public class KieSessionRepo {

    private static   Map<String,KieContainer> kieContainerMap = new ConcurrentHashMap<String,KieContainer>();

    private static  Map<String,KieSession> kieSessionMap= new ConcurrentHashMap<String,KieSession>();
    
    public static  void setKieContainer(String key,KieContainer kieContainer) {
    	KieSession newKieSession = kieContainer.newKieSession();
    	kieContainerMap.put(key, kieContainer);
    	kieSessionMap.put(key,newKieSession);
   }

    public  KieSession getKieSession(String key) {
     
        return kieSessionMap.get(key);
    }
}复制代码

最终执行的结果:

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转载于:https://juejin.im/post/5cf60551f265da1bc07e255c