Running Tables

Running Your Decision Table

This guide shows you how to load and execute a decision table in a Java application.

Creating the Java Application

Let’s create a simple Java application that loads our shipping charges decision table and executes it with test data.

Main Application Class

Create a class called DecisionTableExample.java:

package com.example;

import com.example.model.Charge;
import com.example.model.Order;
import org.kie.api.KieServices;
import org.kie.api.builder.KieBuilder;
import org.kie.api.builder.KieFileSystem;
import org.kie.api.builder.KieRepository;
import org.kie.api.builder.Message.Level;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;
import org.kie.internal.io.ResourceFactory;

import java.util.ArrayList;
import java.util.List;

public class DecisionTableExample {

    public static void main(String[] args) {
        try {
            // Setup KIE resources
            KieServices kieServices = KieServices.Factory.get();
            KieFileSystem kfs = kieServices.newKieFileSystem();
            kfs.write(ResourceFactory.newClassPathResource("rules/ShippingCharges.drl.xlsx"));

            KieBuilder kieBuilder = kieServices.newKieBuilder(kfs);
            kieBuilder.buildAll();

            if (kieBuilder.getResults().hasMessages(Level.ERROR)) {
                throw new RuntimeException("Build Errors:\n" + kieBuilder.getResults().toString());
            }

            KieRepository kieRepository = kieServices.getRepository();
            KieContainer kieContainer = kieServices.newKieContainer(kieRepository.getDefaultReleaseId());

            // Create a new session and run test scenarios
            testShippingCharge(kieContainer, 2, 150.0, 1, "Next-day shipping, under $300, 2 items");
            testShippingCharge(kieContainer, 5, 150.0, 2, "2-day shipping, under $300, 5 items");
            testShippingCharge(kieContainer, 3, 350.0, 3, "Standard shipping, over $300, 3 items");
            testShippingCharge(kieContainer, 5, 400.0, 5, "Standard shipping, over $300, 5 items (free)");

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void testShippingCharge(KieContainer kieContainer, int items, double total, int days, String description) {
        System.out.println("\nTesting: " + description);

        // Create a new session for each test to avoid rule interference
        KieSession kieSession = kieContainer.newKieSession();

        // Create a new order with the test parameters
        Order order = new Order(items, total, days);
        System.out.printf("Order: %d items, $%.2f total, %d delivery days\n",
                order.getItemsCount(), order.getTotal(), order.getDeliverInDays());

        // Insert the facts and fire the rules
        kieSession.insert(order);
        kieSession.fireAllRules();

        // Collect and display results
        List<Charge> charges = new ArrayList<>();
        kieSession.getObjects(obj -> obj instanceof Charge)
                .forEach(obj -> charges.add((Charge) obj));

        if (charges.isEmpty()) {
            System.out.println("No shipping charge calculated!");
        } else {
            System.out.printf("Shipping Charge: $%.2f\n", charges.get(0).getAmount());
        }

        // Clean up
        kieSession.dispose();
    }
}

Understanding the Code

Let’s break down the important parts of this example:

Setup and Build the Knowledge Base

// Setup KIE resources
KieServices kieServices = KieServices.Factory.get();
KieFileSystem kfs = kieServices.newKieFileSystem();
kfs.write(ResourceFactory.newClassPathResource("rules/ShippingCharges.drl.xlsx"));

KieBuilder kieBuilder = kieServices.newKieBuilder(kfs);
kieBuilder.buildAll();

if (kieBuilder.getResults().hasMessages(Level.ERROR)) {
    throw new RuntimeException("Build Errors:\n" + kieBuilder.getResults().toString());
}

KieRepository kieRepository = kieServices.getRepository();
KieContainer kieContainer = kieServices.newKieContainer(kieRepository.getDefaultReleaseId());

This code:

Gets a KIE services instance
Creates a virtual file system to hold the rules
Loads the decision table from the classpath
Builds the knowledge base
Checks for any build errors
Creates a container that holds the compiled rules

Testing with Different Scenarios

testShippingCharge(kieContainer, 2, 150.0, 1, "Next-day shipping, under $300, 2 items");
testShippingCharge(kieContainer, 5, 150.0, 2, "2-day shipping, under $300, 5 items");
testShippingCharge(kieContainer, 3, 350.0, 3, "Standard shipping, over $300, 3 items");
testShippingCharge(kieContainer, 5, 400.0, 5, "Standard shipping, over $300, 5 items (free)");

This runs four different test cases with varying:

Number of items
Order total
Delivery days

The Test Method

private static void testShippingCharge(KieContainer kieContainer, int items, double total, int days, String description) {
    System.out.println("\nTesting: " + description);

    // Create a new session for each test to avoid rule interference
    KieSession kieSession = kieContainer.newKieSession();

    // Create a new order with the test parameters
    Order order = new Order(items, total, days);
    System.out.printf("Order: %d items, $%.2f total, %d delivery days\n",
            order.getItemsCount(), order.getTotal(), order.getDeliverInDays());

    // Insert the facts and fire the rules
    kieSession.insert(order);
    kieSession.fireAllRules();

    // Collect and display results
    List<Charge> charges = new ArrayList<>();
    kieSession.getObjects(obj -> obj instanceof Charge)
            .forEach(obj -> charges.add((Charge) obj));

    if (charges.isEmpty()) {
        System.out.println("No shipping charge calculated!");
    } else {
        System.out.printf("Shipping Charge: $%.2f\n", charges.get(0).getAmount());
    }

    // Clean up
    kieSession.dispose();
}

For each test case, this method:

Creates a new KIE session (a working memory for rules)
Creates an Order object with the test parameters
Inserts the order into the session
Fires all the rules to calculate the shipping charge
Collects any Charge objects that were created
Displays the results
Disposes of the session to free resources

Running the Application

You can run this application by executing the main method in your IDE or by building and running the JAR file.

Expected Output

When you run the application, you should see output similar to this:

Testing: Next-day shipping, under $300, 2 items
Order: 2 items, $150.00 total, 1 delivery days
Shipping Charge: $35.00

Testing: 2-day shipping, under $300, 5 items
Order: 5 items, $150.00 total, 2 delivery days
Shipping Charge: $17.50

Testing: Standard shipping, over $300, 3 items
Order: 3 items, $350.00 total, 3 delivery days
Shipping Charge: $4.50

Testing: Standard shipping, over $300, 5 items (free)
Order: 5 items, $400.00 total, 5 delivery days
Shipping Charge: $0.00

Alternative Loading Method

For simpler applications, you can also use the SpreadsheetCompiler directly:

// Alternative loading method using SpreadsheetCompiler
SpreadsheetCompiler compiler = new SpreadsheetCompiler();
String drl = compiler.compile(ResourceFactory.newClassPathResource("rules/ShippingCharges.drl.xlsx"),
                             InputType.XLS);

KieHelper kieHelper = new KieHelper();
kieHelper.addContent(drl, ResourceType.DRL);
KieContainer kieContainer = kieHelper.getKieContainer();

This method:

Creates a SpreadsheetCompiler instance
Compiles the decision table directly to DRL (Drools Rule Language)
Creates a KieHelper to add the compiled DRL
Gets a KieContainer from the helper

Next Steps

Now that you know how to create and run a decision table, you can:

Modify the existing rules to change the shipping charges
Add more conditions like customer type or destination region
Create more complex decision tables for other business scenarios

In the next section, we’ll explore the RuleSet definitions in more detail.

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Running Tables

Running Your Decision Table

Creating the Java Application

Main Application Class

Understanding the Code

Setup and Build the Knowledge Base

Testing with Different Scenarios

The Test Method

Running the Application

Expected Output

Alternative Loading Method

Next Steps

​Running Your Decision Table

​Creating the Java Application

​Main Application Class

​Understanding the Code

​Setup and Build the Knowledge Base

​Testing with Different Scenarios

​The Test Method

​Running the Application

​Expected Output

​Alternative Loading Method

​Next Steps

Running Your Decision Table

Creating the Java Application

Main Application Class

Understanding the Code

Setup and Build the Knowledge Base

Testing with Different Scenarios

The Test Method

Running the Application

Expected Output

Alternative Loading Method

Next Steps