Spring code explainers

java

@RestController
@RequestMapping("/api/orders")
public class OrderController {

Content-negotiated API versioning in Spring

api-versioning content-negotiation rest

Intermediate 7 steps

java

@Service
public class PaymentGatewayClient {
 
    private static final Logger log = LoggerFactory.getLogger(PaymentGatewayClient.class);

Resilient payment calls in Spring

circuit breaker retry fault tolerance

Intermediate 7 steps

java

@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
public @interface CurrentUser {
}

Injecting the current user in Spring MVC

annotations dependency-injection security

Intermediate 8 steps

java

@RestController
@RequestMapping("/api/products")
@RequiredArgsConstructor
public class ProductSearchController {

Binding paged search filters in Spring

data-binding validation pagination

Intermediate 7 steps

java

@DataJpaTest
@Testcontainers
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
class OrderRepositoryIT {

Testing a JPA repository against real Postgres in Spring

integration-testing testcontainers jpa

Intermediate 8 steps

java

@Aspect
@Component
public class IdempotencyAspect {

How an idempotency aspect works in Spring

aop idempotency caching

Advanced 9 steps

java

package com.example.orders.messaging;
 
import com.example.orders.dto.OrderEvent;
import com.example.orders.service.OrderProcessingService;

Manual RabbitMQ acks in a Spring listener

message-queue error-handling acknowledgement

Intermediate 6 steps

java

package com.example.shop.repository;
 
import com.example.shop.domain.Order;
import com.example.shop.domain.OrderStatus;

Deriving JPA queries from method names in Spring

query derivation repositories pagination

Intermediate 8 steps

java

@RestControllerAdvice
public class GlobalExceptionHandler {
 
    private static final Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class);

Centralized error handling in Spring

exception-handling problemdetail rest-api

Intermediate 7 steps

java

@Component
@Order(20)
public class ProductSearchIndexRunner implements ApplicationRunner {

Rebuilding a search index at Spring startup

startup-hook batching streaming

Intermediate 8 steps

java

@Service
public class OrderCheckoutService {
 
    private final OrderRepository orderRepository;

How @Transactional guards a Spring checkout

dependency-injection transactions atomicity

Intermediate 6 steps

java

@Service
public class OrderMetricsService {
 
    private final MeterRegistry registry;

Instrumenting orders with Micrometer in Spring

metrics micrometer observability

Intermediate 8 steps

java

@RestController
@RequestMapping("/api/files")
public class FileUploadController {

Handling secure file uploads in Spring

file-upload input-validation path-traversal

Intermediate 10 steps

java

package com.example.payments.config;
 
import com.stripe.StripeClient;
import org.springframework.beans.factory.annotation.Value;

Swapping payment gateways by profile in Spring

dependency-injection profiles configuration

Intermediate 6 steps

java

package com.example.maintenance;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

How a scheduled cleanup job runs in Spring

scheduling cron transactions

Intermediate 6 steps

java

@Component
public class RateLimitingFilter extends OncePerRequestFilter {
 
    private static final int MAX_REQUESTS = 100;

How a rate-limiting filter works in Spring

rate limiting concurrency servlet filter

Advanced 8 steps

java

@RestController
@RequestMapping("/api/users")
public class UserController {

How a Spring REST controller maps users

rest-api dependency-injection dto-mapping

Intermediate 7 steps

java

@Service
public class ReportGenerationService {
 
    private final ReportRepository reportRepository;

Async report generation with Spring @Async

async dependency-injection completablefuture

Intermediate 7 steps