Java Todo App - Enterprise Edition

A comprehensive, enterprise-grade todo application built with proper separation of concerns, following SOLID principles and industrial best practices.

🏗️ Architecture Overview

This application follows a layered architecture with clear separation of concerns:

┌─────────────────┐
│   Presentation  │ ← Controllers, DTOs
├─────────────────┤
│   Business      │ ← Services, Domain Models
├─────────────────┤
│   Data Access   │ ← Repository Pattern
├─────────────────┤
│   Infrastructure│ ← Configuration, DI Container
└─────────────────┘

📦 Package Structure

src/main/java/com/todoapp/
├── domain/          # Domain entities and business objects
├── dto/             # Data Transfer Objects for API
├── repository/      # Data access layer (Repository pattern)
├── service/         # Business logic layer
├── controller/      # Presentation layer (REST API)
├── config/          # Configuration and dependency injection
└── exception/       # Custom exception hierarchy

✨ Features

Core Features

• ✅ CRUD Operations: Complete Create, Read, Update, Delete functionality
• ✅ Business Logic: Proper validation and business rules
• ✅ Data Persistence: File-based storage with proper error handling
• ✅ Search & Filter: Advanced search and filtering capabilities
• ✅ Statistics: Real-time completion statistics

Enterprise Features

• 🏢 Separation of Concerns: Clean layered architecture
• 🔧 Dependency Injection: Manual DI container for loose coupling
• 📊 Configuration Management: Externalized configuration
• 🧪 Unit Testing: Comprehensive test coverage with JUnit 5
• 📝 Exception Handling: Proper exception hierarchy
• 🔄 Repository Pattern: Abstracted data access layer
• 📋 DTO Pattern: Clean API contracts
• 🎯 SOLID Principles: Following industry best practices

Interface Options

• 🖥️ Console Interface: Command-line application
• 🌐 Web Interface: Modern responsive web UI
• 🔌 REST API: Full RESTful API endpoints

🚀 Quick Start

Prerequisites

• Java 11 or higher
• Maven 3.6+ (optional, for advanced features)

Option 1: Enterprise Build Script (Recommended)

# Windows
run-enterprise.bat

# Unix/Linux/Mac
chmod +x run-enterprise.sh
./run-enterprise.sh

Option 2: Maven Build

# Compile and run
mvn clean compile
mvn exec:java -Dexec.mainClass="com.todoapp.TodoWebServer"

# Run tests
mvn test

# Package application
mvn package

Option 3: Manual Compilation

# Compile all classes
javac -cp . -d target/classes src/main/java/com/todoapp/**/*.java

# Run console app
java -cp target/classes com.todoapp.TodoConsoleApp

# Run web server
java -cp target/classes com.todoapp.TodoWebServer

🌐 Web Interface

Accessing the Web Interface

1. Start the web server: java -cp target/classes com.todoapp.TodoWebServer
2. Open browser: http://localhost:8080
3. Enjoy the modern, responsive interface!

API Endpoints

Method	Endpoint	Description
GET	/api/todos	Get all todos (with optional filter)
GET	/api/todos?filter=completed	Get completed todos
GET	/api/todos?filter=pending	Get pending todos
POST	/api/todos/add	Create new todo
POST	/api/todos/toggle	Toggle completion status
POST	/api/todos/edit	Update todo
POST	/api/todos/delete	Delete todo
POST	/api/todos/clear-completed	Clear completed todos
GET	/api/stats	Get statistics

🖥️ Console Interface

Available Commands

• add [title:description] - Add a new todo
• list [completed\|pending] - List todos (with optional filter)
• complete <id> - Mark todo as completed
• toggle <id> - Toggle completion status
• edit <id> - Edit a todo
• delete <id> - Delete a todo
• search <query> - Search todos
• clear [completed] - Clear completed todos
• stats - Show statistics
• help - Show help
• quit/exit - Exit application

⚙️ Configuration

The application supports external configuration through:

Configuration Sources (in order of precedence):

1. Environment Variables (e.g., TODOAPP_SERVER_PORT=8080)
2. System Properties (e.g., -Dserver.port=8080)
3. application.properties file
4. Default values

Configuration Properties:

# Server Configuration
server.port=8080
server.host=localhost

# Data Configuration
data.file=todos.txt

# CORS Configuration
cors.enabled=true
cors.allowed.origins=*

# Logging Configuration
logging.level=INFO

# Cache Configuration
cache.enabled=true
cache.size=1000

🧪 Testing

Running Tests

# With Maven
mvn test

# Manual compilation and execution
javac -cp .:junit-platform-console-standalone.jar -d target/test-classes src/test/java/com/todoapp/**/*.java
java -jar junit-platform-console-standalone.jar --class-path target/test-classes

Test Coverage

• Service Layer: Business logic testing with mocked dependencies
• Repository Layer: Data access testing
• Controller Layer: API endpoint testing
• Domain Models: Entity behavior testing

📁 Project Structure

java-todo/
├── src/
│   ├── main/
│   │   ├── java/com/todoapp/
│   │   │   ├── domain/           # Domain entities
│   │   │   ├── dto/              # Data Transfer Objects
│   │   │   ├── repository/       # Data access layer
│   │   │   ├── service/          # Business logic layer
│   │   │   ├── controller/       # REST API controllers
│   │   │   ├── config/           # Configuration & DI
│   │   │   ├── exception/        # Custom exceptions
│   │   │   ├── TodoConsoleApp.java
│   │   │   └── TodoWebServer.java
│   │   └── resources/
│   │       └── application.properties
│   └── test/
│       └── java/com/todoapp/
│           └── service/          # Unit tests
├── pom.xml                       # Maven configuration
├── run-enterprise.bat           # Windows build script
├── run-enterprise.sh            # Unix build script
├── index.html                   # Web interface
└── README.md                    # This file

🔧 Development

Adding New Features

1. Domain Layer: Add business entities and rules
2. Repository Layer: Implement data access methods
3. Service Layer: Add business logic and orchestration
4. Controller Layer: Create API endpoints
5. DTO Layer: Define data transfer objects
6. Tests: Write comprehensive unit tests

Design Patterns Used

• Repository Pattern: Abstract data access
• DTO Pattern: Clean API contracts
• Dependency Injection: Loose coupling
• Factory Pattern: Object creation
• Strategy Pattern: Different implementations
• Observer Pattern: Event handling

🚀 Deployment

Building for Production

# Create executable JAR
mvn clean package

# Run with production profile
java -Dspring.profiles.active=prod -jar target/todo-app.jar

Environment Variables

export TODOAPP_SERVER_PORT=80
export TODOAPP_DATA_FILE=/var/lib/todoapp/todos.txt
export TODOAPP_LOGGING_LEVEL=WARN

📊 Performance Considerations

• Caching: In-memory caching for frequently accessed data
• Connection Pooling: Efficient resource management
• Lazy Loading: Load data only when needed
• Batch Operations: Efficient bulk operations
• Indexing: Optimized data access patterns

🔒 Security Features

• Input Validation: Comprehensive validation at all layers
• SQL Injection Prevention: Parameterized queries
• XSS Protection: Proper output encoding
• CORS Configuration: Configurable cross-origin policies
• Error Handling: Secure error messages

📈 Monitoring & Logging

• Structured Logging: Consistent log format
• Performance Metrics: Built-in performance monitoring
• Health Checks: Application health endpoints
• Audit Trail: Complete operation logging

🤝 Contributing

1. Follow the established package structure
2. Write comprehensive unit tests
3. Follow SOLID principles
4. Use proper exception handling
5. Document public APIs
6. Maintain backward compatibility

📄 License

This project is open source and available under the MIT License.

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Built with ❤️ using enterprise-grade Java architecture patterns