Project Architecture

Multi-Module Structure

SpringBootKafkaWorkshop/
├── spring-boot-kafka-common/    # Shared DTOs and enums
├── spring-boot-kafka-backend/   # REST API + Kafka consumer
├── spring-boot-kafka-frontend/  # Web UI + Kafka producer
├── docker-compose.yml           # Infrastructure
└── pom.xml                      # Parent POM

Module Details

spring-boot-kafka-common

Purpose: Shared code used by both backend and frontend

Contains:

• ProductDTO - Product data transfer object
• PurchaseOrderDTO - Order data transfer object
• ProductOrderDTO - Order line item
• PurchaseOrderStatus - Order status enum

spring-boot-kafka-backend

Port: 8080

Purpose: Business logic, persistence, and Kafka consumer

Key Components:

• Entities: Product, Order, OrderItem (JPA)
• Repositories: Spring Data JPA repositories
• Services: CommandService and QueryService (CQRS)
• Controllers: REST API endpoints
• Kafka Consumer: Processes purchase orders

spring-boot-kafka-frontend

Port: 8081

Purpose: User interface and Kafka producer

Key Components:

• Controllers: Thymeleaf page controllers
• Services: REST client for backend communication
• Kafka Producer: Publishes purchase orders
• Templates: Thymeleaf views with Tailwind CSS

Domain Model

ProductDTO {
    String id (UUID)
    String name
    String description
    Double price
    Integer stock
    String category
}

PurchaseOrderDTO {
    String orderId (UUID)
    String customerId
    List<ProductOrderDTO> products
    Double total
    LocalDateTime orderDate
    PurchaseOrderStatus status
}

Why Multi-Module?

• Code Reuse: Common DTOs shared between modules
• Clear Boundaries: Separation of concerns between layers
• Independent Deployment: Modules can be deployed separately
• Team Organization: Different teams can work on different modules