目的

官方的Drools范例大都是基于纯Java项目或Maven项目，而基于Spring Boot项目的很少。

本文介绍如何在Spring Boot项目上加上Drools规则引擎。

POM依赖

POM文件如下：

<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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.galaxyyao</groupId>
    <artifactId>springbootdroolstest1</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>

    <name>springbootdroolstest1</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.2.RELEASE</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-core</artifactId>
            <version>7.0.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-compiler</artifactId>
            <version>7.0.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-decisiontables</artifactId>
            <version>7.0.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.drools</groupId>
            <artifactId>drools-templates</artifactId>
            <version>7.0.0.Final</version>
        </dependency>

        <dependency>
            <groupId>org.kie</groupId>
            <artifactId>kie-api</artifactId>
            <version>7.0.0.Final</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <configuration>
                    <executable>java</executable>
                    <arguments>
                        <argument>com.galaxyyao.springbootdroolstest1.SpringBootDroolsTest1Application</argument>
                    </arguments>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

其中比较需要注意的是使用了exec-maven-plugin插件，不然无法启动

引用的Drools包的版本可以自行调整。

Resources

在src/main/resources下添加两个目录：

META-INF和rules

META-INF下添加kmodule.xml，内容如下：

<kmodule xmlns="http://jboss.org/kie/6.0.0/kmodule">
   <kbase name="rules" packages="rules">
       <ksession name="ksession-rules"/>
   </kbase>
</kmodule>

rules目录下添加一个简单的Hello World规则

package com.galaxyyao.springbootdroolstest1
import com.galaxyyao.springbootdroolstest1.domain.Message
dialect  "mvel"

rule "Hello World"
    dialect "mvel"
    when
        m : Message(status.equals(Message.HELLO), message : message )
    then
        System.out.println( message);
    modify ( m ) { message = "Goodbye cruel world",status = Message.GOODBYE };
end

rule "Good Bye"
    dialect "java"
    when
       Message( status == Message.GOODBYE, message : message )
    then
        System.out.println( message );
end

Domain层

Domain层定义一个Drools中需要使用到的Model：

package com.galaxyyao.springbootdroolstest1.domain;

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

   private String message;

   private Integer status;

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

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

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

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

Service层

Service层负责实际运行规则：

package com.galaxyyao.springbootdroolstest1.service;

import org.kie.api.KieServices;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;
import org.springframework.stereotype.Service;

import com.galaxyyao.springbootdroolstest1.domain.Message;

@Service
public class DroolsService {
 public String fireRule() {
 // load up the knowledge base
        KieServices ks = KieServices.Factory.get();
        KieContainer kContainer = ks.getKieClasspathContainer();
        KieSession kSession = kContainer.newKieSession("ksession-rules");

       // go !
        Message message = new Message();
        message.setMessage("Hello World");
        message.setStatus(Message.HELLO);
        kSession.insert(message);//插入
        kSession.fireAllRules();//执行规则
        kSession.dispose();
       return message.getMessage();
 }
}