2 first experience of drools

1 Drools First experience

This section uses an example to experience Drools Rule engine writing . Now let's suppose we have a scenario like this ： There is a loan scorecard system , According to some basic conditions of customers （ Age 、 Gender 、 Years of service 、 Monthly income and unit nature, etc ） To give the customer a score , The amount of the final customer is also affected by this score .

1.1 Build the project

Create a simple maven project , project pom.xml Rely on the jar Package coordinates are as follows ：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>drools-demo</artifactId>
        <groupId>com.dream21th</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <artifactId>drools-first</artifactId>
    <dependencies>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-compiler</artifactId>
            <version>7.6.0.Final</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

1.2 Case description

Now suppose there is such a requirement ： If the customer's age is 18 One year old to 60 One year old , Customer score plus 20, In other cases, scores will not be counted ; If the customer's monthly income is 30000 And above plus 20 branch , The monthly income is in 10000 To 30000 Intercalation 10 branch , The monthly income is in 5000 To 10000 Intercalation 5 branch , lower than 5000 Regardless of the score ; If the client is a state-owned enterprise plus 10 branch , Private enterprise plus 8 branch , Foreign enterprises add 5 branch , Other plans 3 branch .

See the above requirements , The most intuitive feeling is , Write a few if else The branch can be done , In fact, for this example , It is implemented by hard coding , It's very simple , But we've talked about , If one day the demand changes , Need to increase the length of service score , Or add the gender type of the enterprise . What to do in case of requirements change ？ If you use hard coding, you can only change the code to test and go online .

1.3 Code implementation

The following uses Drools Rule engine , First, write a business class code to put related attribute parameters , The meanings and code values of related attributes have been explained in the notes .

package com.dream21th.first;

import java.math.BigDecimal;

public class PersonBasicInfo {

    /**
     *  full name 
     */
    private String name;

    /**
     *  Age 
     */
    private Integer age;

    /**
     * Gender   1： male   2： Woman    0： Unknown 
     */
    private String gender;

    /**
     *  Monthly income 
     */
    private BigDecimal monthIn;

    /**
     *  Working years 
     */
    private Integer workAge;

    /**
     *  Unit nature  1： State-owned enterprises   2, Private enterprise   3, foreign   4, other 
     */
    private String companyType;

    /**
     *  The final score 
     */
    private Integer score;


    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public BigDecimal getMonthIn() {
        return monthIn;
    }

    public void setMonthIn(BigDecimal monthIn) {
        this.monthIn = monthIn;
    }

    public Integer getWorkAge() {
        return workAge;
    }

    public void setWorkAge(Integer workAge) {
        this.workAge = workAge;
    }

    public String getCompanyType() {
        return companyType;
    }

    public void setCompanyType(String companyType) {
        this.companyType = companyType;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Integer getScore() {
        return score;
    }

    public void setScore(Integer score) {
        this.score = score;
    }
}

Then write according to the above rules Drools Rules file , There is no detailed description here , The specific rules are as follows , The role of each rule is described in the comments ：

package ruls;
import  com.dream21th.first.PersonBasicInfo
import java.util.Objects;
import java.math.BigDecimal;

/**
*     This rule is to judge age , If the age is 18 To 60 Between , Score plus 20
**/
rule "rule_age"
    when
       $s:PersonBasicInfo(age>18 && age<60)
    then
       Integer score=Objects.isNull($s.getScore())?0+20:$s.getScore()+20;
       $s.setScore(score);
end

/**
*  The following three are the monthly income rules , The income of the current month is greater than 30000 Add 20 branch , stay 10000 To 30000 Intercalation 10 branch , stay 5000 To 10000 Intercalation 5 branch , lower than 5000 No bonus points 
**/
rule "rule_monthIn_0"
    when
       $s:PersonBasicInfo(monthIn.compareTo(BigDecimal.valueOf(30000))>=0)
    then
       Integer score=Objects.isNull($s.getScore())?0+20:$s.getScore()+20;
       $s.setScore(score);
end

rule "rule_monthIn_1"
    when
       $s:PersonBasicInfo(monthIn.compareTo(BigDecimal.valueOf(30000))<0 && monthIn.compareTo(BigDecimal.valueOf(10000))>=0)
    then
       Integer score=Objects.isNull($s.getScore())?0+10:$s.getScore()+10;
       $s.setScore(score);
end

rule "rule_monthIn_2"
    when
       $s:PersonBasicInfo(monthIn.compareTo(BigDecimal.valueOf(10000))<0 && monthIn.compareTo(BigDecimal.valueOf(5000))>=0)
    then
       Integer score=Objects.isNull($s.getScore())?0+5:$s.getScore()+5;
       $s.setScore(score);
end

/**
*   The following are the rules of enterprise nature ：  If it is     1  State-owned enterprises   Add  10
*                                 2  Private enterprise   Add  8
*                                 3  foreign enterprise   Add  5
*                                 4  other   Add  3
**/
rule "rule_companyType_0"
    when
       $s:PersonBasicInfo(companyType=='1')
    then
       Integer score=Objects.isNull($s.getScore())?0+10:$s.getScore()+10;
       $s.setScore(score);
end

rule "rule_companyType_1"
    when
       $s:PersonBasicInfo(companyType=='2')
    then
       Integer score=Objects.isNull($s.getScore())?0+8:$s.getScore()+8;
       $s.setScore(score);
end


rule "rule_companyType_2"
    when
       $s:PersonBasicInfo(companyType=='3')
    then
       Integer score=Objects.isNull($s.getScore())?0+5:$s.getScore()+5;
       $s.setScore(score);
end


rule "rule_companyType_3"
    when
       $s:PersonBasicInfo(companyType=='4')
    then
       Integer score=Objects.isNull($s.getScore())?0+3:$s.getScore()+3;
       $s.setScore(score);
end

Because of the simple maven project , It also needs to be in the resource directory （resources） Let's create a directory META-INF, And create a new file under this directory kmodule.xml, The contents of the document are as follows , This file provides a default for the project kie：

<?xml version="1.0" encoding="UTF-8" ?>
<kmodule xmlns="http://www.drools.org/xsd/kmodule">
    <!--
        name:  Used to specify kbase The name of , You can specify any , But need only 
        packages: Specify the directory of the rule file （ stay resources Below directory ）, Fill in... According to the actual situation , Otherwise, it cannot be loaded into the rule file 
        default: Specify the current kbase Is it the default 
    -->
    <kbase name="myFirst" packages="first" default="true">
        <!--
            name: Appoint ksession name , You can do whatever you want , But need only 
            default: Specify the current session Is it the default 
        -->
        <ksession name="ksession-first" default="true"/>
    </kbase>

</kmodule>

The last step , Create a test case , Write test code ：

package com.dream21th.first;

import org.junit.Test;
import org.kie.api.KieServices;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;
import java.math.BigDecimal;

/*
 * @Author dream21th
 **/
public class DroolsFirstTest {

    @Test
    public void test1(){
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kieClasspathContainer =kieServices.getKieClasspathContainer();
        // Conversation object , Used to interact with the rule engine 
        KieSession kieSession = kieClasspathContainer.newKieSession();

        PersonBasicInfo personBasicInfo=new PersonBasicInfo();
        personBasicInfo.setName(" zhaoyun ");
        personBasicInfo.setAge(34);
        personBasicInfo.setMonthIn(new BigDecimal(100000));
        personBasicInfo.setCompanyType("3");
        kieSession.insert(personBasicInfo);

        // Activate rule engine , If the rule match is successful, execute the rule 
        kieSession.fireAllRules();

        System.out.println(String.format(" Name of customer ：【%s】 The final score ：【%s】",personBasicInfo.getName(),personBasicInfo.getScore()));
        // Close session 
        kieSession.dispose();

    }
}

The age in the example is 34 meter 20 branch , Monthly income 100000 meter 20 branch , Unit nature 3 meter 5 branch , In the end, the total score should be calculated 45 branch , The result of running the code is as follows , The results meet expectations ：

The hierarchy of the whole project is as follows ：