Advanced Java & Spring Boot

Become a job-ready Java backend developer: JDBC, Maven, Spring Core and dependency injection, Spring Boot, REST APIs, validation, JPA and Hibernate, Spring Security with JWT, testing with JUnit, Mockito and MockMvc, microservices with Eureka, Gateway, OpenFeign, Resilience4j and Kafka, and Docker. Every line of code comes from real Spring Boot 4 projects that are built and tested.

1. 01Advanced Java Roadmap, Maven and Your First Spring Boot ProjectWhat "advanced Java" means for a backend job, the order to learn it in, and how a Maven / Spring Boot project is laid out — pom.xml, the Maven wrapper, and the commands you will run every day.
2. 02JDBC — Connecting Java to a Database, PreparedStatement and TransactionsHow Java talks to a database with JDBC: DriverManager, Connection, PreparedStatement and ResultSet, why PreparedStatement stops SQL injection, try-with-resources, commit and rollback, and connection pools.
3. 03Spring Core — IoC Container, Dependency Injection, Beans and ScopesThe idea behind all of Spring: the IoC container creates your objects (beans) and injects what they need. Constructor injection, @Component and @Service, @Primary and @Qualifier, @Bean methods, scopes and the bean lifecycle.
4. 04Spring Boot Basics — Auto-configuration, Starters, application.properties and ProfilesWhat Spring Boot adds on top of Spring: auto-configuration, starters, an embedded server, application.properties, profiles, CommandLineRunner for startup data, and Actuator health checks.
5. 05Building REST APIs with Spring Boot — Controllers, DTOs, HTTP Methods and Status CodesBuild a real CRUD REST API: @RestController and the mapping annotations, path variables and request bodies, records as DTOs, ResponseEntity with the right status codes, and REST design rules interviewers ask about.
6. 06Validation and Exception Handling — @Valid, @RestControllerAdvice and ProblemDetailReject bad input with Bean Validation (@NotBlank, @Min, @Size and @Valid), turn exceptions into clean JSON errors with @RestControllerAdvice, and use RFC 9457 ProblemDetail for 400, 404 and 409 responses.
7. 07Spring Data JPA and Hibernate — Entities, Repositories and QueriesMap Java classes to tables with JPA annotations, get CRUD for free with JpaRepository, write queries just by naming methods, use JPQL with @Query, and understand what Hibernate does for you.
8. 08JPA Relationships and @Transactional — ManyToOne, Lazy Loading, N+1 and Business RulesModel relationships (many-to-one, one-to-many, many-to-many through a join entity), understand lazy loading and the N+1 problem, and keep business rules safe with @Transactional — with a tested enrolment feature.
9. 09Spring Security with JWT — Login, Roles and Stateless APIsSecure a REST API the modern way: password hashing, a login endpoint that issues a signed JWT, Spring Security's OAuth2 resource server to check Bearer tokens, role-based URL rules, and reading the logged-in user — all tested.
10. 10Testing Spring Boot — JUnit 5, Mockito, @WebMvcTest, @DataJpaTest and @SpringBootTestTest a Spring Boot app at every level: fast unit tests with JUnit 5 and Mockito, web-layer slices with @WebMvcTest and MockMvc, repository tests with @DataJpaTest, and full integration tests that log in and call the API.
11. 11API Docs with OpenAPI/Swagger, Logging, Actuator and Production SettingsDocument your API automatically with springdoc OpenAPI and Swagger UI, log properly with SLF4J, monitor with Actuator, and prepare a Spring Boot app for production — configuration, secrets, database migrations and pagination.
12. 12Microservices with Spring Cloud — Monolith vs Microservices, Eureka and API GatewayWhen to split a monolith, how microservices find each other with a Eureka discovery server, and how a Spring Cloud API Gateway routes every request — with tested Spring Boot 4 and Spring Cloud 2025 code.
13. 13Calling Other Services — OpenFeign, Timeouts and Resilience4j Circuit BreakersCall one microservice from another with a declarative OpenFeign client, set timeouts, and survive failures with a Resilience4j circuit breaker and a fallback — tested with a fake service that returns errors.
14. 14Event-Driven Microservices with Apache Kafka and Spring BootWhy services publish events instead of calling each other, Kafka's topics, partitions, offsets and consumer groups, and a tested Spring Boot producer and @KafkaListener consumer sending JSON events.
15. 15Docker for Spring Boot — Dockerfile, Multi-stage Builds and Docker ComposePackage a Spring Boot app as a Docker image with a multi-stage Dockerfile, run as a non-root user, and start the whole microservices system — Kafka, Eureka, gateway and services — with one docker compose command.
16. 16Spring Boot and Microservices Interview Questions — With Short AnswersThe Java backend questions asked in fresher and 0–3 year interviews: Spring core, Spring Boot, REST, JPA and Hibernate, transactions, security and JWT, testing, microservices, Kafka and Docker — short answers linked to the lessons.