Big Bad Monolith

A Jakarta EE sample application implementing a billing platform where users can track billable hours for customers across different categories. Features Derby database integration and comprehensive REST API endpoints.

Features

• DAO pattern with raw JDBC for database persistence
• Embedded Derby database for local development
• Complete billing platform functionality
• User and customer management
• Billable hours tracking with categories
• Billing reports and revenue calculations
• Sample data auto-initialization
• Legacy JSP web interface demonstrating anti-patterns

Domain Model

Core Entities

• User: Represents employees who log billable hours
• Customer: Companies that are billed for services
• BillingCategory: Categories of work with associated hourly rates (e.g., Development, Consulting, Support)
• BillableHour: Individual time entries with hours (BigDecimal), notes, and date logged

Database Schema

users (id, email, name)
customers (id, name, email, address, created_at)
billing_categories (id, name, description, hourly_rate)
billable_hours (id, customer_id, user_id, category_id, hours, note, date_logged, created_at)

Build & Run

# Build the project
./gradlew build

# Run tests
./gradlew test

# Generate WAR file
./gradlew war

Architecture

This application demonstrates a legacy JSP-based architecture with the following anti-patterns:

Data Access Layer

• DAO Pattern: Raw JDBC implementation for database operations
• Connection Management: Manual connection handling (legacy pattern)
• Transaction Management: No explicit transaction boundaries

Presentation Layer (JSP)

• Scriptlets: Java code mixed directly with HTML markup
• Business Logic in JSP: Complex calculations and validations in presentation layer
• Direct DAO Instantiation: DAOs created directly in JSP pages
• Resource Management: Database connections handled in JSP

Anti-Patterns Demonstrated

• Scriptlet Hell: Extensive use of <% %> blocks
• Tight Coupling: Direct instantiation of dependencies
• Mixed Concerns: Presentation, business logic, and data access in same files
• Poor Error Handling: Technical errors exposed to users
• No Input Validation: Raw form parameters used without sanitization

Sample Data

The application automatically initializes with sample data including:

• 2 users (John Doe, Jane Smith)
• 3 customers (Acme Corp, TechStart Inc, MegaCorp Ltd)
• 3 billing categories (Development $150/hr, Consulting$200/hr, Support $100/hr)
• Multiple billable hour entries across different customers and categories

Database

The application uses an embedded Derby database stored in ./data/bigbadmonolith. The database and tables are automatically created on first run using raw JDBC.

Running the Application

Option 1: WebSphere Liberty (Recommended)

Development Mode

# Start Liberty in development mode (auto-reload on changes)
./liberty-dev.sh        # Linux/macOS
liberty-dev.bat         # Windows

Manual Liberty Deployment

# Build the application
./gradlew build

# Start Liberty server with the application
./gradlew libertyStart

# Stop Liberty server
./gradlew libertyStop

Option 2: Other Jakarta EE Application Servers

1. Build: ./gradlew build
2. Deploy the generated WAR file (build/libs/big-bad-monolith-1.0-SNAPSHOT.war) to your Jakarta EE application server
3. Access API at: http://localhost:[port]/big-bad-monolith/api/

Access Points

Web Interface

• Liberty Development: http://localhost:9080/big-bad-monolith/
• Liberty HTTPS: https://localhost:9443/big-bad-monolith/

Web Interface

The application includes a complete JSP-based web interface providing:

• Dashboard - Overview of customers, users, and revenue metrics
• Customer Management - Add, view, and manage customer information
• User Management - Add and view system users
• Billing Categories - Manage work categories and hourly rates
• Time Logging - Log billable hours with detailed tracking
• Reporting - Generate customer bills, monthly summaries, and revenue reports

The web interface demonstrates traditional JSP-based architecture patterns commonly found in legacy enterprise applications that need modernization. The application showcases numerous anti-patterns that training participants will learn to identify and refactor.