Introduction to JDecisiontableLib JDecisiontableLib is an open-source Java library designed to manage, evaluate, and automate decision tables. It helps developers move complex business logic out of hardcoded if-else blocks and into structured, readable tables.
By separating business rules from application code, this library makes software systems easier to maintain, audit, and scale. Core Concepts
A decision table is a structured, tabular format that maps combinations of inputs to specific outputs or actions. JDecisiontableLib models this structure using three primary components:
Conditions: The inputs, rules, or states that need to be evaluated (e.g., UserAge >= 18).
Actions: The outcomes, values, or processes executed when conditions are met (e.g., SetDiscount(0.10)).
Rules: The columns or rows that bind specific condition states to specific actions. Key Features
Lightweight Core: Simple API with minimal external dependencies.
Separation of Concerns: Keeps volatile business logic outside of compiled Java code.
Flexible Input Sources: Supports tables defined via JSON, XML, or Excel spreadsheets.
Type Safety: Strongly typed condition and action checking to catch errors at compile time. Getting Started 1. Define the Decision Table
Tables can be structured in external files (like JSON) or built programmatically.
{ “tableName”: “DiscountRules”, “conditions”: [“IsPremiumMember”, “OrderValueGreaterThan100”], “actions”: [“ApplyDiscount”], “rules”: [ { “inputs”: [true, true], “outputs”: [0.20] }, { “inputs”: [true, false], “outputs”: [0.10] }, { “inputs”: [false, true], “outputs”: [0.05] }, { “inputs”: [false, false], “outputs”: [0.00] } ] } Use code with caution. 2. Evaluate in Java
Load the table file and pass runtime context data to resolve the matching business rule.
// Initialize the engine and load the table DecisionTableEngine engine = new DecisionTableEngine(“DiscountRules.json”); // Create the runtime context map Map context = new HashMap<>(); context.put(“IsPremiumMember”, true); context.put(“OrderValueGreaterThan100”, false); // Evaluate the rules EvaluationResult result = engine.evaluate(context); // Retrieve the action output double discount = result.getOutput(“ApplyDiscount”, Double.class); System.out.println(“Discount applied: ” + (discount100) + “%”); // Outputs 10.0% Use code with caution. Benefits for Development Teams Reduced Code Complexity
Traditional nested conditional logic quickly turns into unreadable “spaghetti code.” JDecisiontableLib flattens these structures into clean, deterministic logic flows that any developer can interpret instantly. Better Collaboration
Because decision tables use a format similar to spreadsheets, developers can share the underlying logic directly with business analysts, product owners, and QA teams. This bridges the gap between technical implementation and business requirements. Faster Updates
When business rules change—such as a tax rate update or a new marketing promotion—you can update the external table configuration file without rebuilding, testing, and redeploying the entire Java application.