Integrating RuleBook with a Spring Boot Microservice

This post guides you through integrating the RuleBook rule engine with your Spring Boot microservice. We’ll cover adding the dependency, configuring RuleBook, and creating a service to utilize it.

1. Project Setup and Dependency

Start by creating a Spring Boot project. Next, add the RuleBook dependency to your pom.xml (Maven) or build.gradle (Gradle) file:

Maven:

<dependency>
    <groupId>org.rulebook</groupId>
    <artifactId>rulebook-core</artifactId>
    <version>5.1.0</version>
</dependency>

Gradle:

implementation 'org.rulebook:rulebook-core:5.1.0'

2. RuleBook Configuration

RuleBook doesn’t require any specific configuration in Spring Boot. Its design promotes defining rules directly within your service classes, leveraging Java 8 lambdas for a concise and readable syntax.

3. Creating RuleBook Rules

Define your rules using RuleBook’s fluent API and lambdas. Here’s an example of a discount rule:

import org.rulebook.core.rule.Rule;

public class DiscountRule {

    public static Rule<Order> applyDiscountRule() {
        return Rule.named("Apply 10% discount for orders over $100")
                .when(order -> order.getTotalPrice() > 100)
                .then(order -> order.applyDiscount(0.1));
    }
}

This code defines a rule named “Apply 10% discount for orders over $100”. It checks if the order’s total price is greater than 100 and applies a 10% discount if the condition is met.

4. Using RuleBook in a Service

Inject the RuleBook bean into your service class and use it to execute rules against your domain objects.

import org.rulebook.core.rule.Rule;
import org.rulebook.core.rulebook.Rulebook;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class OrderService {

    public Order applyRules(Order order) {
        Rule<Order> discountRule = DiscountRule.applyDiscountRule(); 

        // Create a Rulebook and add the rule
        Rulebook<Order> rulebook = Rulebook.of(List.of(discountRule)); 

        // Execute the Rulebook on the order
        rulebook.run(order); 
        return order;
    }
}

This service:

• Retrieves the discountRule defined earlier.
• Creates a Rulebook and adds the discountRule to it.
• Executes the Rulebook on the given order object.
• Returns the potentially modified order object.

5. YML Configuration (Not Required)

RuleBook doesn’t typically require any specific configuration in your application.yml or application.properties file.

This guide demonstrates how to integrate RuleBook with your Spring Boot microservice. RuleBook’s intuitive API and seamless integration with Java 8 lambdas make it a great choice for implementing business rules. You can expand on this by creating more complex rules and rule chains to manage your business logic effectively. Remember to adapt the rules and domain models to your specific requirements.