Drools Using Rules from Excel Files: A Step-by-Step Guide

Are you tired of manually updating your business rules every time there’s a change in your organization? Do you wish you had a more efficient way to manage your rules and keep them up-to-date? Look no further! In this article, we’ll show you how to use Drools to integrate rules from Excel files, making it easier to manage and update your rules.

What is Drools?

Drools is a business rules management system (BRMS) that allows you to define, execute, and maintain complex business rules. It’s an open-source platform that provides a flexible and scalable solution for managing rules in your organization.

With Drools, you can define rules using a variety of languages, including Java, XML, and decision tables. Decision tables are a powerful tool that allows you to define rules in a spreadsheet-like format, making it easy to update and maintain your rules.

What are Decision Tables?

Decision tables are a type of rules representation that uses a tabular format to define rules. They consist of rows and columns, where each row represents a rule and each column represents a condition or action.

Decision tables are easy to create and maintain, and they provide a clear and concise way to define complex rules. With Drools, you can create decision tables in Excel files and then use them to execute rules in your application.

Why Use Excel Files?

Excel files are widely used in organizations to store and manage data. By using Excel files to define rules, you can leverage the power of Drools and simplify the process of managing your rules.

Using Excel files to define rules provides several benefits, including:

• Ease of use: Excel files are easy to create and maintain, making it simple for non-technical users to define and update rules.
• Familiarity: Excel files are widely used, so most users are already familiar with the format and can easily understand and work with decision tables.
• Flexibility: Excel files can be easily shared and updated, making it simple to collaborate with others and keep your rules up-to-date.

Step-by-Step Guide to Using Drools with Excel Files

To get started with using Drools with Excel files, follow these steps:

Step 1: Install Drools

Before you can start using Drools, you need to install it. You can download the Drools installer from the official Drools website.

Once you’ve downloaded the installer, follow the installation instructions to install Drools on your computer.

Step 2: Create an Excel File

Create a new Excel file and give it a name, such as “rules.xlsx”. This file will contain your decision table.

In the Excel file, create a table with the following columns:

• Condition: This column defines the conditions for the rule.
• Action: This column defines the action to take when the conditions are met.
• Priority: This column defines the priority of the rule.

Here’s an example of what the table might look like:

Condition	Action	Priority
Age > 18	Grant access	1
Age <= 18	Deny access	2

Step 3: Define the Rule

In the Excel file, define the rule using the decision table. For example:

Rule "Grant access to adults"
  when
    Age > 18
  then
    Grant access
  priority 1
end

This rule grants access to users who are over 18 years old.

Step 4: Save the Excel File

Save the Excel file and give it a name, such as “rules.xlsx”.

Step 5: Configure Drools

Configure Drools to use the Excel file as a decision table. You can do this by creating a new Drools project and adding the Excel file to the project.

In the Drools editor, create a new decision table and select the Excel file as the source file.

Step 6: Execute the Rule

Execute the rule by creating a new instance of the Drools engine and passing in the decision table.

// Create a new instance of the Drools engine
KieServices kieServices = KieServices.Factory.get();
KieContainer kieContainer = kieServices.getKieClasspathContainer();
KieSession kieSession = kieContainer.newKieSession();

// Pass in the decision table
kieSession.execute("rules.xlsx");

This code creates a new instance of the Drools engine and passes in the decision table from the Excel file.

Step 7: Test the Rule

Test the rule by creating a new instance of the fact and asserting it into the Drools engine.

// Create a new instance of the fact
Person person = new Person();
person.setAge(25);

// Assert the fact into the Drools engine
kieSession.insert(person);

// Fire the rules
kieSession.fireAllRules();

This code creates a new instance of the fact and asserts it into the Drools engine. The Drools engine then fires the rules and grants access to the user.

Benefits of Using Drools with Excel Files

Using Drools with Excel files provides several benefits, including:

• Ease of use: Excel files are easy to create and maintain, making it simple for non-technical users to define and update rules.
• Familiarity: Excel files are widely used, so most users are already familiar with the format and can easily understand and work with decision tables.
• Flexibility: Excel files can be easily shared and updated, making it simple to collaborate with others and keep your rules up-to-date.
• Scalability: Drools provides a scalable solution for managing rules, making it easy to add new rules and update existing ones.

Conclusion

In this article, we’ve shown you how to use Drools with Excel files to define and execute rules. By following these steps, you can create a robust and scalable solution for managing your business rules.

Using Drools with Excel files provides a powerful and flexible solution for managing rules, and it’s easy to get started. With Drools, you can simplify the process of managing your rules and keep them up-to-date, making it easier to make informed decisions in your organization.

Frequently Asked Question

Drools is a business rules management system that allows you to separate business logic from application code, making it a powerful tool for automating decision-making processes. But when it comes to using rules from Excel files, things can get a bit tricky. Here are some frequently asked questions about Drools using rules from Excel files: