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distributed-banking-system
Enterprise-grade microservices banking platform built with Spring Boot 3, Java 21, PostgreSQL, MongoDB, Kafka, and Spring Cloud. Features comprehensive CI/CD, security scanning, and code quality tools.
#apache-kafka#api-gateway#circuit-breaker#distributed-systems#docker#enterprise-architecture
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Enterprise Banking Microservices Platform
Professional Spring Boot microservices architecture demonstrating senior-level design patterns, annotations, and best practices for banking domain.
Architecture Overview
┌─────────────┐
│ Client │
└──────┬──────┘
│
v
┌──────────────────┐ ┌──────────────────┐
│ API Gateway │────▶│ Eureka Server │
│ Port: 8080 │ │ Port: 8761 │
└────────┬─────────┘ └──────────────────┘
│ ▲
│ │
├───────────────────────┼──────────────────┐
│ │ │
v │ v
┌────────────────┐ │ ┌─────────────────┐
│ Account Service│──────────────┘ │ Transaction Svc │
│ Port: 8081 │ │ Port: 8082 │
│ PostgreSQL │ │ MongoDB │
└────────┬───────┘ └────────┬────────┘
│ │
└──────────────┬──────────────────────────┘
│
v
┌───────────┐
│ Kafka │
└─────┬─────┘
│
v
┌──────────────────┐
│Notification Svc │
│ Port: 8083 │
└──────────────────┘
Technologies
- Java 21 (Virtual Threads)
- Spring Boot 3.2.1
- Spring Cloud 2023.0.0
- PostgreSQL 15
- MongoDB 7
- Apache Kafka 7.5
- Docker & Docker Compose
Services
1. Config Server (Port: 8888)
Centralized configuration management for all microservices.
Key Annotations:
@EnableConfigServer- Enables Spring Cloud Config Server@SpringBootApplication- Main application entry point
2. Eureka Server (Port: 8761)
Service discovery and registration server.
Key Annotations:
@EnableEurekaServer- Enables Netflix Eureka service registry
3. API Gateway (Port: 8080)
Single entry point with routing, authentication, and circuit breakers.
Key Annotations:
@EnableDiscoveryClient- Registers with Eureka@Configuration- Defines route configuration@Bean- Creates RouteLocator for custom routing@Component- Marks authentication filter@Order- Controls filter execution order
4. Account Service (Port: 8081)
Core banking operations with PostgreSQL.
Domain Layer:
@Entity- Maps class to database table@Table- Specifies table name and indexes@Id- Marks primary key field@GeneratedValue(strategy=IDENTITY)- Auto-generates ID values@Column- Maps field to database column@Enumerated(EnumType.STRING)- Stores enum as string@ManyToOne- Defines many-to-one relationship@OneToMany- Defines one-to-many relationship@DynamicUpdate- Updates only modified columns@CreatedDate- Auto-populates creation timestamp@LastModifiedDate- Auto-updates modification timestamp@EntityListeners- Enables JPA auditing
Repository Layer:
@Repository- Marks data access component@EntityGraph- Solves N+1 query problem by eager fetching@Query- Defines custom JPQL/SQL queries
Service Layer:
@Service- Marks business logic component@Transactional- Manages database transactions@Validated- Enables method-level validation@RateLimiter- Limits request rate@Bulkhead- Isolates concurrent requests@CircuitBreaker- Prevents cascading failures@TimeLimiter- Sets timeout for operations@Retry- Retries failed operations
Controller Layer:
@RestController- Combines @Controller and @ResponseBody@RequestMapping- Maps URL patterns to controller@GetMapping- Handles HTTP GET requests@PostMapping- Handles HTTP POST requests@PutMapping- Handles HTTP PUT requests@DeleteMapping- Handles HTTP DELETE requests@PathVariable- Extracts values from URL path@RequestParam- Extracts query parameters@RequestBody- Binds request body to object@Valid- Validates request data@PreAuthorize- Enforces method-level security
Configuration:
@Configuration- Declares configuration class@EnableJpaRepositories- Enables JPA repositories@EnableJpaAuditing- Enables auditing for entities@EnableConfigurationProperties- Enables type-safe configuration@ConfigurationProperties- Binds properties to POJO@EnableWebSecurity- Enables Spring Security@EnableMethodSecurity- Enables method-level security@ConditionalOnProperty- Conditionally loads configuration@EnableAsync- Enables asynchronous processing
AOP:
@Aspect- Declares aspect class@Component- Registers aspect as Spring bean@Around- Wraps method execution@Before- Executes before method@AfterReturning- Executes after successful method@AfterThrowing- Executes after exception
Exception Handling:
@RestControllerAdvice- Global exception handler@ExceptionHandler- Handles specific exceptions- Returns
ProblemDetail(RFC 7807 standard)
Messaging:
@Service- Kafka producer component- Uses
KafkaTemplatefor publishing events
Actuator:
@Endpoint- Creates custom actuator endpoint@ReadOperation- Exposes read endpoint@WriteOperation- Exposes write endpoint- Implements
HealthIndicator- Custom health check
Validation:
@NotNull- Field cannot be null@NotBlank- String cannot be empty@Email- Validates email format@Min- Minimum numeric value@Max- Maximum numeric value@Pattern- Validates regex pattern@DecimalMin- Minimum decimal value@DecimalMax- Maximum decimal value
5. Transaction Service (Port: 8082)
Transaction management with MongoDB and reactive programming.
Domain Layer:
@Document- Maps class to MongoDB collection@Id- Marks document identifier@Indexed- Creates MongoDB index@CompoundIndex- Creates compound index@Field- Maps field to document property
Repository Layer:
- Extends
ReactiveMongoRepository- Reactive data access - Returns
Mono<T>- Single reactive result - Returns
Flux<T>- Multiple reactive results
Controller Layer:
@RestController- REST endpoint- Returns reactive types for non-blocking operations
Client:
@FeignClient- Declarative HTTP client- Integrates with Eureka for load balancing
6. Notification Service (Port: 8083)
Event-driven notifications with Kafka consumer.
Configuration:
@Component- Marks configuration component@RefreshScope- Allows dynamic config refresh@ConfigurationProperties- Type-safe configuration
Messaging:
@Component- Kafka consumer component@KafkaListener- Consumes Kafka messages@RetryableTopic- Automatic retry with DLT- Uses
ErrorHandlingDeserializer- Handles poison pills
Service:
@Service- Notification logic@Async- Asynchronous execution with virtual threads
Annotation Reference
| Category | Annotation | Purpose |
|---|---|---|
| Core | @SpringBootApplication | Main application entry combining @Configuration, @EnableAutoConfiguration, @ComponentScan |
@Configuration | Declares configuration class for bean definitions | |
@Bean | Registers method return value as Spring bean | |
@Component | Generic stereotype for Spring-managed component | |
| Stereotype | @Service | Business logic layer component |
@Repository | Data access layer component with exception translation | |
@RestController | REST controller combining @Controller and @ResponseBody | |
| DI | Constructor injection | Preferred dependency injection method (no @Autowired needed for single constructor) |
| Web | @RequestMapping | Maps HTTP requests to handler methods |
@GetMapping | Shortcut for GET requests | |
@PostMapping | Shortcut for POST requests | |
@PathVariable | Extracts URI template variables | |
@RequestParam | Binds query parameters | |
@RequestBody | Binds HTTP request body to object | |
| Validation | @Valid | Triggers JSR-380 validation |
@Validated | Spring validation with group support | |
@NotNull | Field required constraint | |
@Email | Email format constraint | |
| JPA | @Entity | JPA entity class |
@Table | Specifies table details |