In this tutorial, we will create a Spring application and integrate it with JBoss Drools. As with the previous Drools examples, we will create an application for a mobile shop to calculate discounts based on the type of mobile model.
1. Tech Stack
We should have the following software to create/import a drools Project.
- Java 17 or higher version
- Eclipse IDE for Enterprise Java Developers
2. Create Example
The project structure is as follows
Download Spring with drools
Download counts: 2993
Download counts: 2993
- After downloading, unzip the project.
- Go to Eclipse IDE -> File -> Import -> Maven -> Existing Maven project -> Select the project.
Define the model class Product.java as follows.
package com.hi.techpoints.model;
public class Product {
private String model;
private int discount;
public String getModel() {
return model;
}
public void setModel(String model) {
this.model = model;
}
public int getDiscount() {
return discount;
}
public void setDiscount(int discount) {
this.discount = discount;
}
}
The pom.xml will be as follows. Added spring and drools related dependencies
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.hi.techpoints</groupId>
<artifactId>drools-with-spring</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<java.version>17</java.version>
<maven.compiler.target>17</maven.compiler.target>
<maven.compiler.source>17</maven.compiler.source>
<spring.version>6.0.8</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-spring</artifactId>
<version>5.4.0.Final</version>
</dependency>
</dependencies>
</project>
Define the rules.drl as follows
import com.hi.techpoints.model.Product
rule "Offer for Iphone"
when
productObject: Product(model=="Iphone")
then
productObject.setDiscount(20);
end
rule "Offer for Pixel"
when
productObject: Product(model=="Pixel")
then
productObject.setDiscount(30);
end
We define the stateless session for the rules.drl. Define the ProductServiceImpl as follows to get the Stateless session and execute the drools rules.
package com.hi.techpoints.service;
import org.drools.runtime.StatelessKnowledgeSession;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;
import com.hi.techpoints.model.Product;
@Component("ProductServiceImpl")
public class ProductServiceImpl {
@Autowired
private ApplicationContext applicationContext;
public void calculateDiscount(Product product) {
StatelessKnowledgeSession statelessKnowledgeSession = (StatelessKnowledgeSession) applicationContext
.getBean("productSession");
statelessKnowledgeSession.execute(product);
}
}
Define the applicationContext for loading the spring beans.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<import resource="classpath:drools-context.xml"/>
<context:component-scan base-package="com.hi.techpoints" />
</beans>
Finally create the product object and call the ProductServiceImpl CalculateDiscount method to fire the rules for discount.
package com.hi.techpoints;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.hi.techpoints.model.Product;
import com.hi.techpoints.service.ProductServiceImpl;
public class RunDrools {
public static void main(String args[]) {
ApplicationContext applicationContext = new ClassPathXmlApplicationContext(
"applicationContext.xml");
ProductServiceImpl bean = ((ProductServiceImpl) applicationContext
.getBean("ProductServiceImpl"));
Product product = new Product();
product.setModel("Pixel");
bean.calculateDiscount(product);
showDiscount(product);
}
private static void showDiscount(Product product) {
System.out.println("The discount for the product (" + product.getModel() + ") is " + product.getDiscount());
}
}
The output as
