Drools規(guī)則引擎就是根據(jù)規(guī)則判斷和篩選出符合規(guī)則的數(shù)據(jù)。

這哥們講的很生動(dòng)，而且看了一下他的git寫的很不錯(cuò)（收藏了）
https://www.cnblogs.com/ityouknow/archive/2017/08/07/7297524.html
在使用drools時(shí)會(huì)涉及到規(guī)則語法
https://blog.csdn.net/u012373815/article/details/53872025/
drools底層算法rate（看了一下大概是官方文檔的中文版）
https://blog.csdn.net/u012373815/article/details/53869097
入門demo
需求：根據(jù)用戶購買商品的價(jià)格為用戶添加額外的積分

先在resource目錄下創(chuàng)建META-INF目錄
添加kmodule.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://www.drools.org/xsd/kmodule">

    <kbase name="point-rulesKB" packages="rules">
        <ksession name="point-rulesKS"/>
    </kbase>

    <kbase name="HelloWorldKB" packages="rules">
        <ksession name="HelloWorldKS"/>
    </kbase>


</kmodule>

先在resource目錄下創(chuàng)建rules目錄
添加Point-rules.drl文件

<?xml version="1.0" encoding="UTF-8"?>
<kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://www.drools.org/xsd/kmodule">

    <kbase name="point-rulesKB" packages="rules">
        <ksession name="point-rulesKS"/>
    </kbase>

    <kbase name="HelloWorldKB" packages="rules">
        <ksession name="HelloWorldKS"/>
    </kbase>


</kmodule>

如下：

3.png

  <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>

public class Order {
      
    private Date bookingDate;//下單日期
      
    private int amout;//訂單原價(jià)金額  
      
    private User user;//下單人  
      
    private int score;  
      
    public int getScore() {  
        return score;  
    }  
  
    public void setScore(int score) {  
        this.score = score;  
    }  
  
    public Date getBookingDate() {  
        return bookingDate;  
    }  
  
    public void setBookingDate(Date bookingDate) {  
        this.bookingDate = bookingDate;  
    }  
  
    public int getAmout() {  
        return amout;  
    }  
  
    public void setAmout(int amout) {  
        this.amout = amout;  
    }  
  
    public User getUser() {  
        return user;  
    }  
  
    public void setUser(User user) {  
        this.user = user;  
    }  
      
    
}  

public class User {
      
    private String name;//姓名  
      
    private int level;//用戶級(jí)別  
  
    public String getName() {  
        return name;  
    }  
  
    public void setName(String name) {  
        this.name = name;  
    }  
  
    public int getLevel() {  
        return level;  
    }  
  
    public void setLevel(int level) {  
        this.level = level;  
    }  
      
      
      
}  

import org.kie.api.KieServices;
import org.kie.api.event.rule.DebugAgendaEventListener;
import org.kie.api.event.rule.DebugRuleRuntimeEventListener;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;

import java.util.ArrayList;
import java.util.List;

/**
 * This is a sample file to launch a rule package from a rule source file.
 */
public class HelloWorldExample {

    public static final void main(final String[] args) {
        // KieServices is the factory for all KIE services 
        KieServices ks = KieServices.Factory.get();
        
        // From the kie services, a container is created from the classpath
        KieContainer kc = ks.getKieClasspathContainer();

        execute( kc );
    }

    public static void execute( KieContainer kc ) {
        // From the container, a session is created based on
        // its definition and configuration in the META-INF/kmodule.xml file
        KieSession ksession = kc.newKieSession("HelloWorldKS");

        // Once the session is created, the application can interact with it
        // In this case it is setting a global as defined in the
        // org/drools/examples/helloworld/HelloWorld.drl file
        ksession.setGlobal( "list",
                            new ArrayList<Object>() );

        // The application can also setup listeners
        ksession.addEventListener( new DebugAgendaEventListener() );
        ksession.addEventListener( new DebugRuleRuntimeEventListener() );

        // To setup a file based audit logger, uncomment the next line
        // KieRuntimeLogger logger = ks.getLoggers().newFileLogger( ksession, "./helloworld" );

        // To setup a ThreadedFileLogger, so that the audit view reflects events whilst debugging,
        // uncomment the next line
        // KieRuntimeLogger logger = ks.getLoggers().newThreadedFileLogger( ksession, "./helloworld", 1000 );

        // The application can insert facts into the session
        final Message message = new Message();
        message.setMessage( "Hello World" );
        message.setStatus( Message.HELLO );
        ksession.insert( message );

        // and fire the rules
        ksession.fireAllRules();

        // Remove comment if using logging
        // logger.close();

        // and then dispose the session
        ksession.dispose();
    }

    public static class Message {
        public static final int HELLO   = 0;
        public static final int GOODBYE = 1;

        private String          message;

        private int             status;

        public Message() {

        }

        public String getMessage() {
            return this.message;
        }

        public void setMessage(final String message) {
            this.message = message;
        }

        public int getStatus() {
            return this.status;
        }

        public void setStatus(final int status) {
            this.status = status;
        }

        public static Message doSomething(Message message) {
            return message;
        }

        public boolean isSomething(String msg,
                                   List<Object> list) {
            list.add( this );
            return this.message.equals( msg );
        }
    }

}

執(zhí)行main方法輸出：

用戶Name1享受額外增加積分: 0
用戶Name2享受額外增加積分: 100
用戶Name3享受額外增加積分: 500
用戶Name4享受額外增加積分: 1000

Process finished with exit code 0

實(shí)例二

drools 集合操作： List Map

List

helloworld.drl

package helloworld;

import com.neo.drools.model.Person;
import java.util.ArrayList;
import java.util.Map
import java.util.HashSet;
rule "HelloWorld"
    when
        $set:ArrayList();
        $ps:ArrayList()
        $p:Person(age==30) from $ps;
    then
        $set.add($p);
end

java

  KieSession ks = ReloadDroolsRulesService.kieContainer.newKieSession();

        ArrayList<Person> peoples = new ArrayList<Person>();
        peoples.add(new Person("張三",30));
        peoples.add(new Person("李四",40));
        peoples.add(new Person("王五",30));
        ArrayList<Person> new_peoples = new ArrayList<Person>();
        ks.insert(peoples);
        ks.insert(new_peoples);
        ks.fireAllRules();
        System.out.println(new_peoples.toString());
        ks.dispose();

kmodule.xml

<?xml version="1.0" encoding="UTF-8"?>
<kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://www.drools.org/xsd/kmodule">

    <kbase name="rule1KB" packages="com.xu.drools.rule.rule1">
        <ksession name="rule1KS"/>
    </kbase>

    <kbase name="rule2KB" packages="com.xu.drools.rule.rule2">
        <ksession name="rule2KS"/>
    </kbase>

    <kbase name="mingKB" packages="com.xu.drools.rule.complexProblem">
        <ksession name="mingKS"/>
    </kbase>

    <kbase name="worldKB" packages="com.xu.drools.rule.complexProblem">
        <ksession name="worldKS"/>
    </kbase>

    <kbase name="HonestPoliticianKB" packages="com.xu.drools.rule.honestpolitician">
        <ksession name="HonestPoliticianKS"/>
    </kbase>

    <kbase name="mapsKB" packages="com.xu.drools.rule.Map">
        <ksession name="mapsKS"/>
    </kbase>
    <kbase name="listsKB" packages="com.xu.drools.rule.List">
        <ksession name="listsKS"/>
    </kbase>
</kmodule>

Map

maps.drl

package com.rules
import java.util.Map;
import com.xu.drools.bean.Person;

rule "map-usage"

    agenda-group "map-group"

    when
        $obj : Object();
        $map : Map(["p1"] != $obj);
    then
        System.out.println("p1's age is " + ((Person)$map.get("p1")).getAge());
        System.out.println("p2's age is " + ((Person)$map.get("p2")).getAge());
    end

MapTest

package com.xu.drools.rule.complexProblem;

import com.xu.drools.bean.Golfer;
import com.xu.drools.bean.Person;
import org.kie.api.KieServices;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;

import java.util.HashMap;
import java.util.Map;

public class MapTest {
    public static void main(final String[] args) {
        KieContainer kc = KieServices.Factory.get().getKieClasspathContainer();
        System.out.println(kc.verify().getMessages().toString());
        execute(kc);
    }

    private static void execute(KieContainer kc) {
        KieSession ksession = kc.newKieSession("mapsKS");
        ksession.getAgenda().getAgendaGroup("map-group").setFocus();
       // KieSession kieSession = this.getKieSession("map-group");

        Map<String, Person> map = new HashMap<>();
        Person p1 = new Person();
        p1.setAge(10);
        map.put("p1",p1);

        Person p2 = new Person();
        p2.setAge(20);
        map.put("p2",p2);

        ksession.insert(map);

        int count = ksession.fireAllRules();
        System.out.println("Fire " + count + " rule(s)!");

    }
}