Java Spring Microservices

Java Spring Microservices Skill Set

Overview

Enterprise-grade microservices architecture with Spring Boot and Spring Cloud.

When to Use

Architecture

                    ┌─────────────┐
                    │   Gateway   │
                    └──────┬──────┘
           ┌───────────────┼───────────────┐
           ▼               ▼               ▼
    ┌────────────┐  ┌────────────┐  ┌────────────┐
    │    User    │  │   Order    │  │  Payment   │
    │  Service   │  │  Service   │  │  Service   │
    └─────┬──────┘  └─────┬──────┘  └─────┬──────┘
          │               │               │
          ▼               ▼               ▼
    ┌────────────┐  ┌────────────┐  ┌────────────┐
    │  user_db   │  │  order_db  │  │ payment_db │
    └────────────┘  └────────────┘  └────────────┘
          │               │               │
          └───────────────┴───────────────┘
                          │
                    ┌─────▼─────┐
                    │   Kafka   │
                    └─────┬─────┘
                          │
              ┌───────────┴───────────┐
              ▼                       ▼
       ┌────────────┐          ┌────────────┐
       │Notification│          │   Audit    │
       │  Service   │          │  Service   │
       └────────────┘          └────────────┘

Service Types

1. Core Service

Business logic with database.

.\tools\generators\new-service.ps1 -Name "product" -Type "core"

2. Event Service

Kafka consumer only.

.\tools\generators\new-service.ps1 -Name "analytics" -Type "event"

3. Gateway Service

API Gateway with routing.

# Copy from templates
Copy-Item -Path "tools\generators\templates\gateway-service" -Destination "services\gateway-service" -Recurse

4. BFF Service

Backend for Frontend aggregator.

.\tools\generators\new-service.ps1 -Name "web" -Type "bff"

Project Structure

java-spring-microservices/
├── services/                    # Microservices
│   ├── user-service/
│   ├── order-service/
│   ├── payment-service/
│   ├── notification-service/
│   └── gateway-service/
│
├── shared/                      # Shared Libraries
│   ├── common-lib/              # DTOs, Exceptions
│   ├── event-lib/               # Domain Events
│   └── api-contracts/           # OpenAPI specs
│
├── infrastructure/
│   ├── docker/                  # Docker Compose
│   └── kubernetes/              # K8s manifests
│
├── tools/generators/            # Service generator
│
└── docs/architecture/           # Architecture docs

Code Conventions

Package Structure (Core Service)

com.company.{service}/
├── domain/           # Entities, Repositories
├── application/      # Use Cases, DTOs
├── infrastructure/   # JPA, Kafka, Feign
└── interfaces/       # Controllers, Event Handlers

Use Case Pattern

@Slf4j
@Service
@RequiredArgsConstructor
@Transactional
public class CreateOrderUseCase {
    private final OrderRepository repository;
    private final UserServiceClient userClient;
    private final OrderEventPublisher publisher;

    public OrderDto execute(CreateOrderRequest request) {
        // 1. Validate
        var user = userClient.getUserById(request.getUserId());

        // 2. Create
        var order = Order.builder()...build();
        order = repository.save(order);

        // 3. Publish event
        publisher.publishOrderCreated(order);

        return toDto(order);
    }
}

Feign Client

@FeignClient(name = "user-service", fallbackFactory = UserClientFallback.class)
public interface UserServiceClient {
    @GetMapping("/api/users/{id}")
    UserDto getUserById(@PathVariable Long id);
}

Event Publishing

kafkaTemplate.send("order-events", OrderCreatedEvent.builder()
    .orderId(order.getId())
    .userId(order.getUserId())
    .build());

Communication

Commands

# Start infrastructure
cd infrastructure/docker && docker-compose up -d

# Create new service
.\tools\generators\new-service.ps1 -Name "product" -Type "core"

# Build all
mvn clean package

# Deploy to K8s
kubectl apply -k infrastructure/kubernetes/base

Documentation

• QUICKSTART.md - Get started in 10 minutes
• Architecture Overview
• Event Flows
• API Contracts