Shopping Application Backend

A robust, microservices-based backend for an e-commerce shopping application built with Spring Boot. This project demonstrates modern software architecture principles, including service decomposition, event-driven communication, distributed tracing, and API gateway pattern.

🏗️ Architecture

The application follows a microservices architecture with the following components:

• API Gateway: Centralized entry point for all client requests, handling routing, authentication, and load balancing using Spring Cloud Gateway.
• User Service: Manages user registration, authentication, and authorization with JWT tokens.
• Item Service: Handles product catalog management, including CRUD operations for items.
• Order Service: Processes shopping orders, integrates with Redis for caching, and publishes events to Kafka.
• Audit Service: Consumes audit events from Kafka and persists them in MongoDB for compliance and monitoring.

Architecture Diagram

[Client] → [API Gateway] → [User Service]
                    ↓
              [Item Service] ← [Order Service] → [Kafka] → [Audit Service]
                    ↓
              [MySQL]        [Redis]              [MongoDB]

🚀 Features

• Microservices Design: Modular, independently deployable services
• API Gateway: Centralized routing and cross-cutting concerns
• Authentication & Authorization: JWT-based security
• Event-Driven Architecture: Asynchronous communication via Apache Kafka
• Distributed Caching: Redis for performance optimization
• Observability: OpenTelemetry tracing and metrics collection
• API Documentation: Swagger/OpenAPI integration
• Database Variety: MySQL, MongoDB, H2, and Redis for different use cases

🛠️ Technology Stack

• Framework: Spring Boot 3.x
• Language: Java 21
• API Gateway: Spring Cloud Gateway
• Messaging: Apache Kafka
• Databases: MySQL, MongoDB, H2
• Caching: Redis
• Security: Spring Security, JWT
• Observability: OpenTelemetry, Micrometer
• Documentation: SpringDoc OpenAPI
• Build Tool: Maven
• Containerization: Docker (partial)

📋 Prerequisites

Before running the application, ensure you have the following installed:

• Java 21
• Maven 3.6+
• MySQL 8.0+
• MongoDB 4.0+
• Redis 6.0+
• Apache Kafka 2.8+
• Docker

🔧 Installation & Setup

1. Clone the repository:

   git clone https://github.com/your-username/shopping-app-backend.git
   cd shopping-app-backend

2. Start Infrastructure Services:

   • Start MySQL, MongoDB, Redis, and Kafka (using Docker or local installations)
   • Configure connection details in respective application.properties files

3. Build all services:

   # Build each service
   cd apigateway && mvn clean install
   cd ../user-service && mvn clean install
   cd ../item-service && mvn clean install
   cd ../order-service && mvn clean install
   cd ../audit-service && mvn clean install

▶️ Running the Application

Start services in the following order:

1. Start Infrastructure (Kafka, Redis, Databases)

2. Start Audit Service (listens for events):

   cd audit-service
   mvn spring-boot:run

3. Start User Service:

   cd user-service
   mvn spring-boot:run

4. Start Item Service:

   cd item-service
   mvn spring-boot:run

5. Start Order Service:

   cd order-service
   mvn spring-boot:run

6. Start API Gateway:

   cd apigateway
   mvn spring-boot:run

The API Gateway will be available at http://localhost:4001

📚 API Documentation

• User Service: http://localhost:4002/user-swagger-ui
• Item Service: http://localhost:4003/user-swagger-ui

🔍 Service Ports

• API Gateway: 4001
• User Service: 4002
• Item Service: 4003
• Order Service: 4004
• Audit Service: 4005

This project showcases expertise in microservices architecture, Spring ecosystem, event-driven systems, and cloud-native development practices.