规则引擎drools的简单使用

<dependency>
    <groupId>org.drools</groupId>
    <artifactId>drools-core</artifactId>
    <version>7.13.0.Final</version>
</dependency>
<dependency>
    <groupId>org.drools</groupId>
    <artifactId>drools-compiler</artifactId>
    <version>7.13.0.Final</version>
</dependency>

package com.beyond.odc.entity;

/**
 * Fact java bean
 * @author Hejinsheng
 */
public class Message 

    private String message;

    private String result;

    private int status;

    public String getMessage() 
        return this.message;
    

    public void setMessage(String message) 
        this.message = message;
    

    public int getStatus() 
        return this.status;
    

    public void setStatus(int status) 
        this.status = status;
    

    public String getResult() 
        return result;
    

    public void setResult(String result) 
        this.result = result;
    

<?xml version="1.0" encoding="UTF-8"?>
<kmodule xmlns="http://jboss.org/kie/6.0.0/kmodule">
    <kbase name="rules" packages="rules">
        <ksession name="ksession-rules"/>
    </kbase>
</kmodule>

package rules

import com.beyond.odc.entity.Message;

rule "hello"
    no-loop true
    lock-on-active true
    when
        $message:Message(status==0)
    then
        System.out.println("消息："+$message.getMessage());
        $message.setResult("hello 响应的消息");
        update($message)
end

rule "byebye"
    no-loop true
    lock-on-active true
    when
        $message:Message(status==1)
    then
        System.out.println("消息："+$message.getMessage());
        $message.setResult("byebye 响应的消息");
        update($message)
end

public static void main(String[] args) 
       try 

            KieSession kSession = KieContainerFactory.getKieContainer().newKieSession("ksession-rules");

            Message message = new Message();
            message.setMessage("hello");    // 对应drl文件中的rule name，表示要执行的规则
            message.setStatus(0);           // 取message中的某个字段，用户规则文件中的判断是否执行代码块
            kSession.insert(message);       // 将message作为传递的参数传入drools执行
            kSession.fireAllRules();        // 加载规则
            System.out.println("从drools中接收到的消息："+message.getResult());    // drools中如果有参数响应，可以通过字段获取
         catch (Throwable t) 
            t.printStackTrace();
        

//KieContainerFactory代码片段
public class KieContainerFactory 

    private static KieContainer kieContainer;

    public static KieContainer getKieContainer() 
        if(kieContainer == null)
            // load up the knowledge base
            KieServices ks = KieServices.Factory.get();
            KieContainer kContainer = ks.getKieClasspathContainer();
            kieContainer = kContainer;
        
        return kieContainer;
    

进来了，消息：hello
从drools中接收到的消息：hello 响应的消息

public static void execFromDB()
        KieSession kSession = null;
        try 
            // 实际情况从数据库根据code查规则，这里模拟写死
            String rule = "package rules
" +
                    "
" +
                    "import com.beyond.odc.entity.Message;
" +
                    "
" +
                    "rule "hello"
" +
                    "    no-loop true
" +
                    "    lock-on-active true
" +
                    "    when
" +
                    "        $message:Message(status==0)
" +
                    "    then
" +
                    "        System.out.println("动态执行，消息："+$message.getMessage());
" +
                    "        $message.setResult("hello 响应的消息");
" +
                    "        update($message)
" +
                    "end
" +
                    "
" +
                    "rule "byebye"
" +
                    "    no-loop true
" +
                    "    lock-on-active true
" +
                    "    when
" +
                    "        $message:Message(status==1)
" +
                    "    then
" +
                    "        System.out.println("动态执行，消息："+$message.getMessage());
" +
                    "        $message.setResult("byebye 响应的消息");
" +
                    "        update($message)
" +
                    "end";

            KnowledgeBuilder kb = KnowledgeBuilderFactory.newKnowledgeBuilder();
            kb.add(ResourceFactory.newByteArrayResource(rule.getBytes("utf-8")), ResourceType.DRL);

            // 检查规则正确性
            KnowledgeBuilderErrors errors = kb.getErrors();
            for (KnowledgeBuilderError error : errors) 
                System.out.println("规则文件正确性有误：" + error);
            
            InternalKnowledgeBase kBase = KnowledgeBaseFactory.newKnowledgeBase();
            kBase.addPackages(kb.getKnowledgePackages());

            // 执行规则
            kSession = kBase.newKieSession();
            // fact
            Message fact = new Message();
            fact.setMessage("byebye");
            fact.setStatus(1);
            kSession.insert(fact);
            kSession.fireAllRules();
            System.out.println("从drools规则中接收到的消息："+fact.getResult());
         catch (Exception e) 
            System.out.println("规则执行异常："+e);
         finally 
            if (null != kSession)
                kSession.dispose();
        

    

动态执行，消息：byebye
从drools规则中接收到的消息：byebye 响应的消息