Drools BRMS in Mule ESB

What is DROOLS?

DROOLS is a Rules Engine supported by JBoss and Red Hat, It executes statements that might modify the state of the objects, depending on which rules satisfy the input. It is very powerful tool that we can use to change the state of an object by specifying various condition based statement through which the object pass and a refined and cleaned object is achieved. Drools is a best-of-breed open source Rules Engine which also offers Complex Event Processing.

Within Mule, input is fed to the rules engine from within a flow, and the rules execute to modify the state of that input. Below is the sample of one such flow. We will be covering more about it how to achieve Drools implementation in Mule ESB.

Considerations

{
  "name": "Harish Kumar",
  "age":30,
  "purchase":19000
}

<mule xmlns:bpm="http://www.mulesoft.org/schema/mule/bpm" xsi:schemaLocation="http://www.mulesoft.org/schema/mule/bpm http://www.mulesoft.org/schema/mule/bpm/3.7/mule-bpm.xsd">
</mule>

Initialisation of BPM

Add below tag to your droolsdemo.xml, this tag will tell mule that you will be using Rules Engine and will startup Drools’ working memory and all your rules and keep them ready to be called

<bpm:drools />

Mule Flow

As explained earlier we will be getting a JSON object and we will convert it into a Java object using mule JSON to Object transformer. Our java class represent the customer object and looks like below

package com.drools.demo;
import java.math.BigDecimal;

public class Customer {

	private String name;
	private int age;
	private BigDecimal purchase;
	private String customerType;

	public String getName() {
		return name;
	}

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

	public int getAge() {
		return age;
	}

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

	public BigDecimal getPurchase() {
		return purchase;
	}

	public void setPurchase(BigDecimal purchase) {
		this.purchase = purchase;
	}

	public String getCustomerType() {
		return customerType;
	}

	public void setCustomerType(String customerType) {
		this.customerType = customerType;
	}

}

Rule Definiton Statements

In drools we write our logic in a file with the extension of .drl , This file contains your business logic in plan text format that could be easily changed and loaded at runtime if the need be. This file should be available at your project classpath to be loaded by mule at project startup.

package com.drools.demo
import org.mule.MessageExchangePattern;
import com.drools.demo.Customer;

global org.mule.module.bpm.MessageService mule;

dialect "mvel"

declare Customer
	@role('event')
end

rule "Decide Platinum Customer"
	lock-on-active
when
	$customer : Customer(purchase >= 10000)
then
	modify($customer) {setCustomerType("Platinum")}
end

rule "Decide Gold Customer"
	lock-on-active
when
	$customer : Customer(purchase >= 5000 && purchase < 10000)
then
	modify($customer) {setCustomerType("Gold")}
end

rule "Decide Silver Customer"
	lock-on-active
when
	$customer : Customer(purchase< 5000)
then
	modify($customer) {setCustomerType("Silver")}
end

In the starting part of this rule file we define the general things like imports and package. Than we create a object of our customer to be used by our rule statements and then comes the juicy part of RULES, what we are saying here is a when condition based on which if it passes the object is changed with a new state.

Usage of drl in flow

<bpm:rules rulesDefinition="customerGroup.drl" initialFacts-ref="NoFactsBean" doc:name="BPM Rules" />

here we use the drl file that we created and implement the rules in middle of our flow.

Complete flow

So now we are done with the setting of flow the complete droolsdemo.xml will looks like below.

<?xml version="1.0" encoding="UTF-8"?>
<mule ...>
	<http:listener-config name="HTTP_Listener_Configuration" 		host="0.0.0.0" port="8081" doc:name="HTTP Listener Configuration" />

	<bpm:drools/>

	<spring:beans>
        <spring:bean name="NoFactsBean" class="java.util.ArrayList"/>
    </spring:beans>

	<flow name="droolsdemoFlow">
		<http:listener config-ref="HTTP_Listener_Configuration" 			path="/brtest" allowedMethods="POST" doc:name="HTTP" />
		<object-to-string-transformer doc:name="Object to String" />
		<json:json-to-object-transformer 			returnClass="com.drools.demo.Customer" doc:name="JSON to Object" />
		<bpm:rules rulesDefinition="customerGroup.drl" 			initialFacts-ref="NoFactsBean" doc:name="BPM Rules" />
        <set-payload value="#[payload.object]" doc:name="Set Payload"/>
        <json:object-to-json-transformer doc:name="Object to JSON"/>
	</flow>
</mule>

Testing

We will be  sending three different JSON input to our flow inbound http endpoint, and hopefully will get the correct rules fired and proper grade back for our customer.

• Purchase above 10000

• Between 5000 and 10000

  

• Below 5000

  

So we can see for all three cases the correct rule was applied and a proper grading or customer type was given to our Customer object.

Video

I have created the same implementation in a youtube video that you can watch at this link https://www.youtube.com/watch?v=1OgzLdEayLw

References

More details about Drools in Mule is available at https://docs.mulesoft.com/mule-user-guide/v/3.7/drools-module-reference

I hope that you found this blog interesting and that it helps you with your integration of Mule and JBoss Drools. If you liked this blog please comment and follow this site and if you liked the video of tutorial please share and subscribe it will encourage me to write and create more awesome stuff and blogs.