Drools学习（1-入门例子）

1.新建一个Maven项目

项目结构如图:

安装依赖:
在pom.xml文件中添加

    <dependencies>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-core</artifactId>
            <version>6.5.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-nop</artifactId>
            <version>1.7.2</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-compiler</artifactId>
            <version>6.5.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.3.2</version>
        </dependency>
    </dependencies>

在resources下面新建文件夹META-INF用于注册规则，同时新建文件夹demoRules用于存放规则drl文件（这里文件名自己随意定），然后再src的java目录下，建立自己的项目包和java类，这个根据个人喜好。


2.编写简单的例子

创建一个Student类，作为规则要用到的fact

package com.daigua.models;

public class Student {
    private String name;
    private int age;
    private String gender;

    public Student(String name, int age, String gender) {
        this.name = name;
        this.age = age;
        this.gender = gender;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public String getGender() {
        return gender;
    }

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

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

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

编写一个简单的规则:如果学生名字是daigua，就打印你好呀，呆瓜！

package demoRuls

import com.daigua.models.Student

rule "student_name"
when
    $s : Student(name == "daigua")
then
    System.out.println("你好呀，呆瓜！");
end

注册规则:

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

    <!--注册规则-->
    <kbase name="Demo1KB" packages="demoRules">
        <ksession name="Demo1KS"/>
    </kbase>

</kmodule>

使用drools的api进行简单规则测试:

package com.daigua.demos;


import com.daigua.models.Student;
import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseConfiguration;
import org.drools.KnowledgeBaseFactory;
import org.drools.builder.*;
import org.drools.definition.KnowledgePackage;
import org.drools.io.ResourceFactory;
import org.drools.runtime.StatefulKnowledgeSession;

import java.util.Collection;

public class MyDroolsDemo1 {
    public static void main(String[] args) {
        // 规则编译器
        KnowledgeBuilder kb = KnowledgeBuilderFactory.newKnowledgeBuilder();

        // 添加规则，并编译
        kb.add(ResourceFactory.newClassPathResource("demoRules/Demo1.drl"), ResourceType.DRL);

        // 检查规则是否有错误
        if(kb.hasErrors()){
            KnowledgeBuilderErrors errors = kb.getErrors();

            for (KnowledgeBuilderError error : errors) {
                System.out.println("error = " + error);
            }
        }
        // 得到规则包
        Collection<KnowledgePackage> kPackage = kb.getKnowledgePackages();
        System.out.println("kPackage = " + kPackage);
        // kPackage = [[Package name=demoRuls], [Package name=com.daigua.models]]


        // 修改属性,创建替换文件
        KnowledgeBaseConfiguration kbc = KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
        kbc.setProperty("org.drools.sequential", "true");
        System.out.println("kbc = " + kbc);

        // 创建base
        KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(kbc);
        // 加入包
        kbase.addKnowledgePackages(kPackage);
        // 得到session
        StatefulKnowledgeSession knowledgeSession = kbase.newStatefulKnowledgeSession();

        // 创建一个global
//        knowledgeSession.setGlobal("testGlobal", new Object());

        // 插入fact对象
        knowledgeSession.insert(new Student("daigua", 18, "male"));

        knowledgeSession.fireAllRules();

        knowledgeSession.dispose();

    }

}

运行后输出的结果会是:


3.使用kie接口

package com.daigua.demos;


import com.daigua.models.Student;
import org.kie.api.KieServices;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;

// 使用kie的api
public class MyDroolsDemo2 {

    public static void main(String[] args) {

        KieServices ks = KieServices.Factory.get();

        KieContainer kc = ks.getKieClasspathContainer();

        KieSession kSession = kc.newKieSession("Demo1KS");  // 这里对应注册文件中的ksession标签

        kSession.insert(new Student("daigua", 18, "female"));
        kSession.fireAllRules();
        kSession.fireAllRules();
        
    }
}

可以看到代码变得简洁了很多