Stack: Spring Boot 3.4.4 · Java 21 · Spring Framework 6 · Jakarta EE 10

A comprehensive, hands-on reference covering every major Spring Boot concept — from basics to production-grade patterns. Each module is a self-contained, runnable project.

This project has been upgraded from Spring Boot 2.x to Spring Boot 3.4.4 running on Java 21. Key changes:

# Clone
git clone https://github.com/sandipsmenon/spring-boot-tutorial.git
cd spring-boot-tutorial

# Run any module (example: H2 in-memory CRUD — no DB setup needed)
cd springboot2-jpa-h2-crud-example
mvn spring-boot:run

Modules that need MySQL/PostgreSQL/MSSQL require a running database. Update src/main/resources/application.properties with your credentials before running.

• Auto-configuration (@SpringBootApplication, @EnableAutoConfiguration)
• Dependency Injection: annotation config, Java @Configuration, XML config
• Bean lifecycle & scopes
• application.properties / application.yml, profiles (@Profile)
• @PropertySource, @ConfigurationProperties, @Value

• @RestController, @GetMapping, @PostMapping, @PutMapping, @DeleteMapping
• ResponseEntity, @RequestBody, @PathVariable, @RequestParam
• Global exception handling (@ControllerAdvice, @ExceptionHandler)
• Bean Validation (@Valid, @NotNull, @Size, @Email)
• OpenAPI 3 documentation with SpringDoc

• Spring Data JPA (JpaRepository, CrudRepository, PagingAndSortingRepository)
• Hibernate ORM (entity mappings, relationships, composite keys)
• JPA Auditing (@EnableJpaAuditing, @CreatedDate, @LastModifiedDate)
• Spring JDBC Template
• MyBatis
• Spring Data MongoDB
• Multiple DataSources

• @OneToOne, @OneToMany, @ManyToOne, @ManyToMany
• Cascade types, fetch strategies (EAGER/LAZY)
• @JoinColumn, @JoinTable
• @EmbeddedId composite keys

• Spring MVC (@Controller, @RequestMapping, Model, ModelAndView)
• Thymeleaf (templates, fragments, layouts, form binding)
• JSP + JSTL
• FreeMarker
• Form validation in MVC (@Valid, BindingResult)
• WAR deployment to external Tomcat

• HTTP Basic & form-based authentication
• Role-based access control (@PreAuthorize, hasRole())
• UserDetailsService, PasswordEncoder (BCrypt)
• CSRF protection
• Security with Thymeleaf (thymeleaf-extras-springsecurity6)
• User registration & login flows

• @Aspect, @Pointcut
• Advice types: @Before, @After, @AfterReturning, @AfterThrowing, @Around
• Use cases: logging, performance monitoring, transactions

• @EnableAsync, @Async
• CompletableFuture return types
• Custom thread pool (ThreadPoolTaskExecutor)

• JMS with ActiveMQ (@JmsListener, JmsTemplate)
• WebSocket with STOMP (@MessageMapping, SimpMessagingTemplate)
• Real-time messaging to browser clients

• Multipart file upload (@RequestParam MultipartFile)
• File download (InputStreamResource, ByteArrayResource)
• Storing files in database (as BLOB)
• Storing files in filesystem

• @SpringBootTest (full integration tests)
• @WebMvcTest (controller slice tests)
• @DataJpaTest (repository slice tests)
• MockMvc, TestRestTemplate, WebTestClient
• JUnit 5 (@Test, @BeforeEach, @ExtendWith, @ParameterizedTest)
• Mockito (@Mock, @MockBean, @InjectMocks)

• SLF4J + Logback (default in Spring Boot)
• Log4j2 configuration
• Log levels, rolling file appenders
• Spring Boot Actuator endpoints (/actuator/health, /actuator/info, /actuator/metrics)

• SpringDoc OpenAPI 3 (@Operation, @ApiResponse, @Schema)
• Swagger UI at /swagger-ui/index.html
• OpenAPI JSON spec at /v3/api-docs

• CORS configuration (@CrossOrigin, CorsConfigurationSource)
• Spring Boot as REST backend for Angular / React / Vue
• WebJars for serving frontend libraries (Bootstrap, jQuery)

Each module follows standard Maven layout:

module-name/
├── src/
│   ├── main/
│   │   ├── java/         # Application code
│   │   └── resources/
│   │       └── application.properties
│   └── test/
│       └── java/         # Test code
└── pom.xml

Pull requests welcome. Please keep each module focused on demonstrating a single Spring Boot concept.

This project is open-source and available for educational use.