Spring Boot Engineering Hub

Spring Boot is VMware/Broadcom's production-ready, opinionated framework built on top of the Spring Framework ecosystem. Designed around the principle of "Convention over Configuration", Spring Boot enables developers to build self-contained, enterprise-grade Java web applications and microservices with minimal manual configuration.

• Analogy: A Fully Equipped Ghost Kitchen & Turn-Key Smart Factory.
  • Traditional Spring Framework: Building a commercial kitchen from scratch—buying stoves, installing gas lines, running ventilation, wiring electrical systems, and assembling XML configuration blueprints before cooking your first dish.
  • Spring Boot: A turn-key, pre-configured commercial ghost kitchen container. Plug it into power (java -jar app.jar), turn the key, and start cooking immediately.
  • Auto-Configuration (@EnableAutoConfiguration): The smart building system that detects ingredients on the shelf (dependencies on classpath) and automatically configures appliances (beans) without manual wiring.
  • Embedded Tomcat Server: The built-in power generator and reception desk packaged directly inside your container—no external server installation required.

---

🗺️ Spring Boot Digital Textbook Modules & Navigation Roadmap

Explore our structured, modular Spring Boot masterclass below. Organized like a digital textbook, each module covers deep architectural mechanics, request lifecycles, code examples, debugging strategies, and production best practices.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

Module 14: Soft Delete Architecture & JPA Filtering

• 14.1 Logical Deletion Semantics & Entity Mapping: Hard delete (DELETE) vs Soft delete (PATCH /soft-delete), archive cabinet analogy, physical existence vs application visibility, @Column(name = "is_deleted"), and state machine transitions.
• 14.2 Derived Query Methods & The findById Trap: The findAll() and findById() data leakage traps, derived query syntax (findByIsDeletedFalse, findByIdAndIsDeletedFalse), and 3-step soft delete execution pipeline.

Module 15: Soft Delete Production Patterns & Indexing

• 15.1 Controller-Service Pipeline & PATCH Semantics: REST @PatchMapping("/{id}/soft-delete") controller boundary, @Transactional service state mutations, complete reference code implementation, and end-to-end mental model.
• 15.2 Indexing, Anti-Patterns & Refactoring: Database indexing caveats for low-cardinality boolean flags, composite index solutions, operational query complexity matrix, 7 production pitfalls, and API refactoring.

Module 16: Servlets Architecture & Container Lifecycle

• 16.1 Servlets Fundamentals & Restaurant Analogy: Java Servlets fundamentals, Restaurant Kitchen mental model, why raw ServerSocket is insufficient, static vs dynamic sites, and Servlet container IoC.
• 16.2 Servlet Lifecycle, Concurrency & Request Pipeline: Complete 4-phase lifecycle pipeline (init, service, destroy), single-instance multithreaded concurrency hazards, and HttpServletRequest/HttpServletResponse abstractions.

Module 17: Servlet Deployment & Spring MVC Progression

• 17.1 WAR Packaging, Provided Scope & Embedded Tomcat: Web Application Archive (.war) structure, Maven <scope>provided</scope> classloader isolation rule, external Tomcat administration, and Spring Boot embedded container model.
• 17.2 DispatcherServlet, Spring MVC & Production Pitfalls: Traditional Servlet scaling bottlenecks, DispatcherServlet Front Controller pattern, 6-stage architectural progression, production pitfalls matrix, and debugging challenges.

Module 18: Spring MVC Core Architecture & Dispatching

• 18.1 Front Controller & DispatcherServlet: Spring Web MVC fundamentals, Airport Control Tower mental model, Front Controller pattern vs multi-servlet chaos, and @Controller vs @RestController.
• 18.2 HandlerMapping, HandlerAdapter & Argument Resolution: Startup-time mapping metadata construction, HandlerAdapter invocation, method argument resolution (@PathVariable, @RequestParam, @RequestBody), and Jackson HttpMessageConverter.

Module 19: Manual Spring MVC, JSP & Spring Boot Auto-Config

• 19.1 Manual Spring MVC & Embedded Tomcat Bootstrap: Manual dependency triad (spring-webmvc, tomcat-embed-core, jackson-databind), @EnableWebMvc setup, AnnotationConfigWebApplicationContext, DispatcherServlet registration, and App.java blueprint.
• 19.2 ViewResolver, JSP Pipeline & Spring Boot Automation: InternalResourceViewResolver, JSP pipeline, WEB-INF security boundary, Spring Boot auto-configuration, and in-memory HashMap vs database complexity.

Module 20: DTOs & Architectural Boundary Decoupling

• 20.1 Entity Exposure Hazards & Security Gate Model: Building Security Gate mental model, mass assignment vulnerabilities, sensitive data leakage, Entity vs DTO comparison matrix, and architectural boundary rules.
• 20.2 Request/Response DTOs & Mapping Pipelines: Request DTO vs Response DTO specifications, explicit service mapping functions (mapToEntity, mapToResponseDto), and production CRUD controller implementations.

Module 21: Bean Validation & API Contract Enforcement

• 21.1 Bean Validation Annotations & @Valid Trigger: spring-boot-starter-validation, @NotBlank vs @NotNull vs @NotEmpty comparison matrix, @Valid validation trigger, and skip-service execution pipeline.
• 21.2 Error Contracts, Anti-Patterns & Refactoring: HTTP 400 Bad Request semantics, structured validation error response contracts, production anti-patterns matrix, and refactoring entity-coupled CRUD APIs.

Module 22: HTTP Response Semantics & Custom Exceptions

• 22.1 HTTP Response Anatomy & ResponseEntity: Emergency Department mental model, HTTP status taxonomy (200, 201, 204, 400, 404, 409, 500), decision matrix, and ResponseEntity construction.
• 22.2 Custom Exceptions & Service-Layer Signaling: Why error handling must leave controllers, domain unchecked exceptions (ResourceNotFoundException, DuplicateResourceException), and Optional.orElseThrow() signals.

Module 23: Global Exception Handling & Error Contracts

• 23.1 @RestControllerAdvice & Exception Mappings: @RestControllerAdvice vs @ControllerAdvice, ErrorResponseDto envelope, request URI logging, and 400 Bad Request vs 409 Conflict critical distinction.
• 23.2 Validation Errors, Parsing & Production Safety: Handling MethodArgumentNotValidException with fieldErrors, malformed JSON parsing errors, production stack trace leakage security, and exception handler hierarchy.

Module 24: Externalized Configuration, Properties & YAML

• 24.1 Configuration Fundamentals & Properties vs YAML: Hotel Control Panel mental model, code vs config vs secrets boundaries, application.properties key-value spreadsheets, YAML indentation rules, and list representations.
• 24.2 Configuration Binding: @Value vs @ConfigurationProperties: Single property injection with @Value, type-safe grouped binding with @ConfigurationProperties, relaxed binding mechanics, and database/JPA configuration blueprints.

Module 25: Spring Profiles & Environment Decoupling

• 25.1 Profile-Specific Configuration & Activation: Profiles as operating modes (dev, test, prod), application-{profile}.yml override hierarchy, activation mechanisms (CLI, env vars), and build-once-deploy-anywhere principles.
• 25.2 Conditional Beans with @Profile & Production Patterns: Changing values (profile files) vs changing beans (@Profile), interface implementation switching (DevNotificationService vs ProdNotificationService), resolving bean ambiguity, and production anti-patterns.

Module 26: Servlet Filters & Request Interception Pipeline

• 26.1 Servlet Filter Fundamentals & Lifecycle: Security Checkpoint mental model, request pipeline execution, jakarta.servlet.Filter lifecycle, Spring Boot 3 namespace migration, and cross-cutting concerns matrix.
• 26.2 doFilter Continuation, Blocking & Ordering: chain.doFilter() continuation vs early request blocking, casting ServletRequest to HttpServletRequest, @Order execution stack, and DispatcherServlet boundary rules.

Module 27: Production Filter Patterns & Security

• 27.1 Production Logging, Timing & Trace IDs: Request logging filter blueprint, guaranteed timing with try-finally, correlation trace IDs (X-Request-Id), response commitment rules, and sensitive data logging security.
• 27.2 Blocking, Anti-Patterns & Thread-Safety: Early request rejection with direct JSON error responses (401 Unauthorized), thread-safety singleton rules, production anti-patterns, and architectural decision trees.

Module 28: Request/Response Wrappers & Body Caching

• 28.1 Response Mutation & ContentCachingResponseWrapper: Response headers, response commitment rules, sealed envelope mental model, ContentCachingResponseWrapper, resetBuffer(), and copyBodyToResponse().
• 28.2 Request Wrappers & Repeatable Body Caching: HttpServletRequestWrapper header/parameter substitution, stream consumption rules, Tape Recorder model, classic filter stream bug, and CachedBodyHttpServletRequest re-readable body caching blueprint.

Module 29: Advanced Filter Registration & OncePerRequestFilter

• 29.1 FilterRegistrationBean & URL Scoping: @Component vs FilterRegistrationBean, explicit URL mapping (/api/*), preventing duplicate filter registration bugs, and URL scoping strategies.
• 29.2 OncePerRequestFilter & Architectural Layer Selection: OncePerRequestFilter, doFilterInternal(), shouldNotFilter(), Servlet dispatch types (REQUEST, ASYNC, ERROR), and complete architectural layer selection map.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

Module 14: Soft Delete Architecture & JPA Filtering

• 14.1 Logical Deletion Semantics & Entity Mapping: Hard delete (DELETE) vs Soft delete (PATCH /soft-delete), archive cabinet analogy, physical existence vs application visibility, @Column(name = "is_deleted"), and state machine transitions.
• 14.2 Derived Query Methods & The findById Trap: The findAll() and findById() data leakage traps, derived query syntax (findByIsDeletedFalse, findByIdAndIsDeletedFalse), and 3-step soft delete execution pipeline.

Module 15: Soft Delete Production Patterns & Indexing

• 15.1 Controller-Service Pipeline & PATCH Semantics: REST @PatchMapping("/{id}/soft-delete") controller boundary, @Transactional service state mutations, complete reference code implementation, and end-to-end mental model.
• 15.2 Indexing, Anti-Patterns & Refactoring: Database indexing caveats for low-cardinality boolean flags, composite index solutions, operational query complexity matrix, 7 production pitfalls, and API refactoring.

Module 16: Servlets Architecture & Container Lifecycle

• 16.1 Servlets Fundamentals & Restaurant Analogy: Java Servlets fundamentals, Restaurant Kitchen mental model, why raw ServerSocket is insufficient, static vs dynamic sites, and Servlet container IoC.
• 16.2 Servlet Lifecycle, Concurrency & Request Pipeline: Complete 4-phase lifecycle pipeline (init, service, destroy), single-instance multithreaded concurrency hazards, and HttpServletRequest/HttpServletResponse abstractions.

Module 17: Servlet Deployment & Spring MVC Progression

• 17.1 WAR Packaging, Provided Scope & Embedded Tomcat: Web Application Archive (.war) structure, Maven <scope>provided</scope> classloader isolation rule, external Tomcat administration, and Spring Boot embedded container model.
• 17.2 DispatcherServlet, Spring MVC & Production Pitfalls: Traditional Servlet scaling bottlenecks, DispatcherServlet Front Controller pattern, 6-stage architectural progression, production pitfalls matrix, and debugging challenges.

Module 18: Spring MVC Core Architecture & Dispatching

• 18.1 Front Controller & DispatcherServlet: Spring Web MVC fundamentals, Airport Control Tower mental model, Front Controller pattern vs multi-servlet chaos, and @Controller vs @RestController.
• 18.2 HandlerMapping, HandlerAdapter & Argument Resolution: Startup-time mapping metadata construction, HandlerAdapter invocation, method argument resolution (@PathVariable, @RequestParam, @RequestBody), and Jackson HttpMessageConverter.

Module 19: Manual Spring MVC, JSP & Spring Boot Auto-Config

• 19.1 Manual Spring MVC & Embedded Tomcat Bootstrap: Manual dependency triad (spring-webmvc, tomcat-embed-core, jackson-databind), @EnableWebMvc setup, AnnotationConfigWebApplicationContext, DispatcherServlet registration, and App.java blueprint.
• 19.2 ViewResolver, JSP Pipeline & Spring Boot Automation: InternalResourceViewResolver, JSP pipeline, WEB-INF security boundary, Spring Boot auto-configuration, and in-memory HashMap vs database complexity.

Module 20: DTOs & Architectural Boundary Decoupling

• 20.1 Entity Exposure Hazards & Security Gate Model: Building Security Gate mental model, mass assignment vulnerabilities, sensitive data leakage, Entity vs DTO comparison matrix, and architectural boundary rules.
• 20.2 Request/Response DTOs & Mapping Pipelines: Request DTO vs Response DTO specifications, explicit service mapping functions (mapToEntity, mapToResponseDto), and production CRUD controller implementations.

Module 21: Bean Validation & API Contract Enforcement

• 21.1 Bean Validation Annotations & @Valid Trigger: spring-boot-starter-validation, @NotBlank vs @NotNull vs @NotEmpty comparison matrix, @Valid validation trigger, and skip-service execution pipeline.
• 21.2 Error Contracts, Anti-Patterns & Refactoring: HTTP 400 Bad Request semantics, structured validation error response contracts, production anti-patterns matrix, and refactoring entity-coupled CRUD APIs.

Module 22: HTTP Response Semantics & Custom Exceptions

• 22.1 HTTP Response Anatomy & ResponseEntity: Emergency Department mental model, HTTP status taxonomy (200, 201, 204, 400, 404, 409, 500), decision matrix, and ResponseEntity construction.
• 22.2 Custom Exceptions & Service-Layer Signaling: Why error handling must leave controllers, domain unchecked exceptions (ResourceNotFoundException, DuplicateResourceException), and Optional.orElseThrow() signals.

Module 23: Global Exception Handling & Error Contracts

• 23.1 @RestControllerAdvice & Exception Mappings: @RestControllerAdvice vs @ControllerAdvice, ErrorResponseDto envelope, request URI logging, and 400 Bad Request vs 409 Conflict critical distinction.
• 23.2 Validation Errors, Parsing & Production Safety: Handling MethodArgumentNotValidException with fieldErrors, malformed JSON parsing errors, production stack trace leakage security, and exception handler hierarchy.

Module 24: Externalized Configuration, Properties & YAML

• 24.1 Configuration Fundamentals & Properties vs YAML: Hotel Control Panel mental model, code vs config vs secrets boundaries, application.properties key-value spreadsheets, YAML indentation rules, and list representations.
• 24.2 Configuration Binding: @Value vs @ConfigurationProperties: Single property injection with @Value, type-safe grouped binding with @ConfigurationProperties, relaxed binding mechanics, and database/JPA configuration blueprints.

Module 25: Spring Profiles & Environment Decoupling

• 25.1 Profile-Specific Configuration & Activation: Profiles as operating modes (dev, test, prod), application-{profile}.yml override hierarchy, activation mechanisms (CLI, env vars), and build-once-deploy-anywhere principles.
• 25.2 Conditional Beans with @Profile & Production Patterns: Changing values (profile files) vs changing beans (@Profile), interface implementation switching (DevNotificationService vs ProdNotificationService), resolving bean ambiguity, and production anti-patterns.

Module 26: Servlet Filters & Request Interception Pipeline

• 26.1 Servlet Filter Fundamentals & Lifecycle: Security Checkpoint mental model, request pipeline execution, jakarta.servlet.Filter lifecycle, Spring Boot 3 namespace migration, and cross-cutting concerns matrix.
• 26.2 doFilter Continuation, Blocking & Ordering: chain.doFilter() continuation vs early request blocking, casting ServletRequest to HttpServletRequest, @Order execution stack, and DispatcherServlet boundary rules.

Module 27: Production Filter Patterns & Security

• 27.1 Production Logging, Timing & Trace IDs: Request logging filter blueprint, guaranteed timing with try-finally, correlation trace IDs (X-Request-Id), response commitment rules, and sensitive data logging security.
• 27.2 Blocking, Anti-Patterns & Thread-Safety: Early request rejection with direct JSON error responses (401 Unauthorized), thread-safety singleton rules, production anti-patterns, and architectural decision trees.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

Module 14: Soft Delete Architecture & JPA Filtering

• 14.1 Logical Deletion Semantics & Entity Mapping: Hard delete (DELETE) vs Soft delete (PATCH /soft-delete), archive cabinet analogy, physical existence vs application visibility, @Column(name = "is_deleted"), and state machine transitions.
• 14.2 Derived Query Methods & The findById Trap: The findAll() and findById() data leakage traps, derived query syntax (findByIsDeletedFalse, findByIdAndIsDeletedFalse), and 3-step soft delete execution pipeline.

Module 15: Soft Delete Production Patterns & Indexing

• 15.1 Controller-Service Pipeline & PATCH Semantics: REST @PatchMapping("/{id}/soft-delete") controller boundary, @Transactional service state mutations, complete reference code implementation, and end-to-end mental model.
• 15.2 Indexing, Anti-Patterns & Refactoring: Database indexing caveats for low-cardinality boolean flags, composite index solutions, operational query complexity matrix, 7 production pitfalls, and API refactoring.

Module 16: Servlets Architecture & Container Lifecycle

• 16.1 Servlets Fundamentals & Restaurant Analogy: Java Servlets fundamentals, Restaurant Kitchen mental model, why raw ServerSocket is insufficient, static vs dynamic sites, and Servlet container IoC.
• 16.2 Servlet Lifecycle, Concurrency & Request Pipeline: Complete 4-phase lifecycle pipeline (init, service, destroy), single-instance multithreaded concurrency hazards, and HttpServletRequest/HttpServletResponse abstractions.

Module 17: Servlet Deployment & Spring MVC Progression

• 17.1 WAR Packaging, Provided Scope & Embedded Tomcat: Web Application Archive (.war) structure, Maven <scope>provided</scope> classloader isolation rule, external Tomcat administration, and Spring Boot embedded container model.
• 17.2 DispatcherServlet, Spring MVC & Production Pitfalls: Traditional Servlet scaling bottlenecks, DispatcherServlet Front Controller pattern, 6-stage architectural progression, production pitfalls matrix, and debugging challenges.

Module 18: Spring MVC Core Architecture & Dispatching

• 18.1 Front Controller & DispatcherServlet: Spring Web MVC fundamentals, Airport Control Tower mental model, Front Controller pattern vs multi-servlet chaos, and @Controller vs @RestController.
• 18.2 HandlerMapping, HandlerAdapter & Argument Resolution: Startup-time mapping metadata construction, HandlerAdapter invocation, method argument resolution (@PathVariable, @RequestParam, @RequestBody), and Jackson HttpMessageConverter.

Module 19: Manual Spring MVC, JSP & Spring Boot Auto-Config

• 19.1 Manual Spring MVC & Embedded Tomcat Bootstrap: Manual dependency triad (spring-webmvc, tomcat-embed-core, jackson-databind), @EnableWebMvc setup, AnnotationConfigWebApplicationContext, DispatcherServlet registration, and App.java blueprint.
• 19.2 ViewResolver, JSP Pipeline & Spring Boot Automation: InternalResourceViewResolver, JSP pipeline, WEB-INF security boundary, Spring Boot auto-configuration, and in-memory HashMap vs database complexity.

Module 20: DTOs & Architectural Boundary Decoupling

• 20.1 Entity Exposure Hazards & Security Gate Model: Building Security Gate mental model, mass assignment vulnerabilities, sensitive data leakage, Entity vs DTO comparison matrix, and architectural boundary rules.
• 20.2 Request/Response DTOs & Mapping Pipelines: Request DTO vs Response DTO specifications, explicit service mapping functions (mapToEntity, mapToResponseDto), and production CRUD controller implementations.

Module 21: Bean Validation & API Contract Enforcement

• 21.1 Bean Validation Annotations & @Valid Trigger: spring-boot-starter-validation, @NotBlank vs @NotNull vs @NotEmpty comparison matrix, @Valid validation trigger, and skip-service execution pipeline.
• 21.2 Error Contracts, Anti-Patterns & Refactoring: HTTP 400 Bad Request semantics, structured validation error response contracts, production anti-patterns matrix, and refactoring entity-coupled CRUD APIs.

Module 22: HTTP Response Semantics & Custom Exceptions

• 22.1 HTTP Response Anatomy & ResponseEntity: Emergency Department mental model, HTTP status taxonomy (200, 201, 204, 400, 404, 409, 500), decision matrix, and ResponseEntity construction.
• 22.2 Custom Exceptions & Service-Layer Signaling: Why error handling must leave controllers, domain unchecked exceptions (ResourceNotFoundException, DuplicateResourceException), and Optional.orElseThrow() signals.

Module 23: Global Exception Handling & Error Contracts

• 23.1 @RestControllerAdvice & Exception Mappings: @RestControllerAdvice vs @ControllerAdvice, ErrorResponseDto envelope, request URI logging, and 400 Bad Request vs 409 Conflict critical distinction.
• 23.2 Validation Errors, Parsing & Production Safety: Handling MethodArgumentNotValidException with fieldErrors, malformed JSON parsing errors, production stack trace leakage security, and exception handler hierarchy.

Module 24: Externalized Configuration, Properties & YAML

• 24.1 Configuration Fundamentals & Properties vs YAML: Hotel Control Panel mental model, code vs config vs secrets boundaries, application.properties key-value spreadsheets, YAML indentation rules, and list representations.
• 24.2 Configuration Binding: @Value vs @ConfigurationProperties: Single property injection with @Value, type-safe grouped binding with @ConfigurationProperties, relaxed binding mechanics, and database/JPA configuration blueprints.

Module 25: Spring Profiles & Environment Decoupling

• 25.1 Profile-Specific Configuration & Activation: Profiles as operating modes (dev, test, prod), application-{profile}.yml override hierarchy, activation mechanisms (CLI, env vars), and build-once-deploy-anywhere principles.
• 25.2 Conditional Beans with @Profile & Production Patterns: Changing values (profile files) vs changing beans (@Profile), interface implementation switching (DevNotificationService vs ProdNotificationService), resolving bean ambiguity, and production anti-patterns.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

Module 14: Soft Delete Architecture & JPA Filtering

• 14.1 Logical Deletion Semantics & Entity Mapping: Hard delete (DELETE) vs Soft delete (PATCH /soft-delete), archive cabinet analogy, physical existence vs application visibility, @Column(name = "is_deleted"), and state machine transitions.
• 14.2 Derived Query Methods & The findById Trap: The findAll() and findById() data leakage traps, derived query syntax (findByIsDeletedFalse, findByIdAndIsDeletedFalse), and 3-step soft delete execution pipeline.

Module 15: Soft Delete Production Patterns & Indexing

• 15.1 Controller-Service Pipeline & PATCH Semantics: REST @PatchMapping("/{id}/soft-delete") controller boundary, @Transactional service state mutations, complete reference code implementation, and end-to-end mental model.
• 15.2 Indexing, Anti-Patterns & Refactoring: Database indexing caveats for low-cardinality boolean flags, composite index solutions, operational query complexity matrix, 7 production pitfalls, and API refactoring.

Module 16: Servlets Architecture & Container Lifecycle

• 16.1 Servlets Fundamentals & Restaurant Analogy: Java Servlets fundamentals, Restaurant Kitchen mental model, why raw ServerSocket is insufficient, static vs dynamic sites, and Servlet container IoC.
• 16.2 Servlet Lifecycle, Concurrency & Request Pipeline: Complete 4-phase lifecycle pipeline (init, service, destroy), single-instance multithreaded concurrency hazards, and HttpServletRequest/HttpServletResponse abstractions.

Module 17: Servlet Deployment & Spring MVC Progression

• 17.1 WAR Packaging, Provided Scope & Embedded Tomcat: Web Application Archive (.war) structure, Maven <scope>provided</scope> classloader isolation rule, external Tomcat administration, and Spring Boot embedded container model.
• 17.2 DispatcherServlet, Spring MVC & Production Pitfalls: Traditional Servlet scaling bottlenecks, DispatcherServlet Front Controller pattern, 6-stage architectural progression, production pitfalls matrix, and debugging challenges.

Module 18: Spring MVC Core Architecture & Dispatching

• 18.1 Front Controller & DispatcherServlet: Spring Web MVC fundamentals, Airport Control Tower mental model, Front Controller pattern vs multi-servlet chaos, and @Controller vs @RestController.
• 18.2 HandlerMapping, HandlerAdapter & Argument Resolution: Startup-time mapping metadata construction, HandlerAdapter invocation, method argument resolution (@PathVariable, @RequestParam, @RequestBody), and Jackson HttpMessageConverter.

Module 19: Manual Spring MVC, JSP & Spring Boot Auto-Config

• 19.1 Manual Spring MVC & Embedded Tomcat Bootstrap: Manual dependency triad (spring-webmvc, tomcat-embed-core, jackson-databind), @EnableWebMvc setup, AnnotationConfigWebApplicationContext, DispatcherServlet registration, and App.java blueprint.
• 19.2 ViewResolver, JSP Pipeline & Spring Boot Automation: InternalResourceViewResolver, JSP pipeline, WEB-INF security boundary, Spring Boot auto-configuration, and in-memory HashMap vs database complexity.

Module 20: DTOs & Architectural Boundary Decoupling

• 20.1 Entity Exposure Hazards & Security Gate Model: Building Security Gate mental model, mass assignment vulnerabilities, sensitive data leakage, Entity vs DTO comparison matrix, and architectural boundary rules.
• 20.2 Request/Response DTOs & Mapping Pipelines: Request DTO vs Response DTO specifications, explicit service mapping functions (mapToEntity, mapToResponseDto), and production CRUD controller implementations.

Module 21: Bean Validation & API Contract Enforcement

• 21.1 Bean Validation Annotations & @Valid Trigger: spring-boot-starter-validation, @NotBlank vs @NotNull vs @NotEmpty comparison matrix, @Valid validation trigger, and skip-service execution pipeline.
• 21.2 Error Contracts, Anti-Patterns & Refactoring: HTTP 400 Bad Request semantics, structured validation error response contracts, production anti-patterns matrix, and refactoring entity-coupled CRUD APIs.

Module 22: HTTP Response Semantics & Custom Exceptions

• 22.1 HTTP Response Anatomy & ResponseEntity: Emergency Department mental model, HTTP status taxonomy (200, 201, 204, 400, 404, 409, 500), decision matrix, and ResponseEntity construction.
• 22.2 Custom Exceptions & Service-Layer Signaling: Why error handling must leave controllers, domain unchecked exceptions (ResourceNotFoundException, DuplicateResourceException), and Optional.orElseThrow() signals.

Module 23: Global Exception Handling & Error Contracts

• 23.1 @RestControllerAdvice & Exception Mappings: @RestControllerAdvice vs @ControllerAdvice, ErrorResponseDto envelope, request URI logging, and 400 Bad Request vs 409 Conflict critical distinction.
• 23.2 Validation Errors, Parsing & Production Safety: Handling MethodArgumentNotValidException with fieldErrors, malformed JSON parsing errors, production stack trace leakage security, and exception handler hierarchy.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

Module 14: Soft Delete Architecture & JPA Filtering

• 14.1 Logical Deletion Semantics & Entity Mapping: Hard delete (DELETE) vs Soft delete (PATCH /soft-delete), archive cabinet analogy, physical existence vs application visibility, @Column(name = "is_deleted"), and state machine transitions.
• 14.2 Derived Query Methods & The findById Trap: The findAll() and findById() data leakage traps, derived query syntax (findByIsDeletedFalse, findByIdAndIsDeletedFalse), and 3-step soft delete execution pipeline.

Module 15: Soft Delete Production Patterns & Indexing

• 15.1 Controller-Service Pipeline & PATCH Semantics: REST @PatchMapping("/{id}/soft-delete") controller boundary, @Transactional service state mutations, complete reference code implementation, and end-to-end mental model.
• 15.2 Indexing, Anti-Patterns & Refactoring: Database indexing caveats for low-cardinality boolean flags, composite index solutions, operational query complexity matrix, 7 production pitfalls, and API refactoring.

Module 16: Servlets Architecture & Container Lifecycle

• 16.1 Servlets Fundamentals & Restaurant Analogy: Java Servlets fundamentals, Restaurant Kitchen mental model, why raw ServerSocket is insufficient, static vs dynamic sites, and Servlet container IoC.
• 16.2 Servlet Lifecycle, Concurrency & Request Pipeline: Complete 4-phase lifecycle pipeline (init, service, destroy), single-instance multithreaded concurrency hazards, and HttpServletRequest/HttpServletResponse abstractions.

Module 17: Servlet Deployment & Spring MVC Progression

• 17.1 WAR Packaging, Provided Scope & Embedded Tomcat: Web Application Archive (.war) structure, Maven <scope>provided</scope> classloader isolation rule, external Tomcat administration, and Spring Boot embedded container model.
• 17.2 DispatcherServlet, Spring MVC & Production Pitfalls: Traditional Servlet scaling bottlenecks, DispatcherServlet Front Controller pattern, 6-stage architectural progression, production pitfalls matrix, and debugging challenges.

Module 18: Spring MVC Core Architecture & Dispatching

• 18.1 Front Controller & DispatcherServlet: Spring Web MVC fundamentals, Airport Control Tower mental model, Front Controller pattern vs multi-servlet chaos, and @Controller vs @RestController.
• 18.2 HandlerMapping, HandlerAdapter & Argument Resolution: Startup-time mapping metadata construction, HandlerAdapter invocation, method argument resolution (@PathVariable, @RequestParam, @RequestBody), and Jackson HttpMessageConverter.

Module 19: Manual Spring MVC, JSP & Spring Boot Auto-Config

• 19.1 Manual Spring MVC & Embedded Tomcat Bootstrap: Manual dependency triad (spring-webmvc, tomcat-embed-core, jackson-databind), @EnableWebMvc setup, AnnotationConfigWebApplicationContext, DispatcherServlet registration, and App.java blueprint.
• 19.2 ViewResolver, JSP Pipeline & Spring Boot Automation: InternalResourceViewResolver, JSP pipeline, WEB-INF security boundary, Spring Boot auto-configuration, and in-memory HashMap vs database complexity.

Module 20: DTOs & Architectural Boundary Decoupling

• 20.1 Entity Exposure Hazards & Security Gate Model: Building Security Gate mental model, mass assignment vulnerabilities, sensitive data leakage, Entity vs DTO comparison matrix, and architectural boundary rules.
• 20.2 Request/Response DTOs & Mapping Pipelines: Request DTO vs Response DTO specifications, explicit service mapping functions (mapToEntity, mapToResponseDto), and production CRUD controller implementations.

Module 21: Bean Validation & API Contract Enforcement

• 21.1 Bean Validation Annotations & @Valid Trigger: spring-boot-starter-validation, @NotBlank vs @NotNull vs @NotEmpty comparison matrix, @Valid validation trigger, and skip-service execution pipeline.
• 21.2 Error Contracts, Anti-Patterns & Refactoring: HTTP 400 Bad Request semantics, structured validation error response contracts, production anti-patterns matrix, and refactoring entity-coupled CRUD APIs.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

Module 14: Soft Delete Architecture & JPA Filtering

• 14.1 Logical Deletion Semantics & Entity Mapping: Hard delete (DELETE) vs Soft delete (PATCH /soft-delete), archive cabinet analogy, physical existence vs application visibility, @Column(name = "is_deleted"), and state machine transitions.
• 14.2 Derived Query Methods & The findById Trap: The findAll() and findById() data leakage traps, derived query syntax (findByIsDeletedFalse, findByIdAndIsDeletedFalse), and 3-step soft delete execution pipeline.

Module 15: Soft Delete Production Patterns & Indexing

• 15.1 Controller-Service Pipeline & PATCH Semantics: REST @PatchMapping("/{id}/soft-delete") controller boundary, @Transactional service state mutations, complete reference code implementation, and end-to-end mental model.
• 15.2 Indexing, Anti-Patterns & Refactoring: Database indexing caveats for low-cardinality boolean flags, composite index solutions, operational query complexity matrix, 7 production pitfalls, and API refactoring.

Module 16: Servlets Architecture & Container Lifecycle

• 16.1 Servlets Fundamentals & Restaurant Analogy: Java Servlets fundamentals, Restaurant Kitchen mental model, why raw ServerSocket is insufficient, static vs dynamic sites, and Servlet container IoC.
• 16.2 Servlet Lifecycle, Concurrency & Request Pipeline: Complete 4-phase lifecycle pipeline (init, service, destroy), single-instance multithreaded concurrency hazards, and HttpServletRequest/HttpServletResponse abstractions.

Module 17: Servlet Deployment & Spring MVC Progression

• 17.1 WAR Packaging, Provided Scope & Embedded Tomcat: Web Application Archive (.war) structure, Maven <scope>provided</scope> classloader isolation rule, external Tomcat administration, and Spring Boot embedded container model.
• 17.2 DispatcherServlet, Spring MVC & Production Pitfalls: Traditional Servlet scaling bottlenecks, DispatcherServlet Front Controller pattern, 6-stage architectural progression, production pitfalls matrix, and debugging challenges.

Module 18: Spring MVC Core Architecture & Dispatching

• 18.1 Front Controller & DispatcherServlet: Spring Web MVC fundamentals, Airport Control Tower mental model, Front Controller pattern vs multi-servlet chaos, and @Controller vs @RestController.
• 18.2 HandlerMapping, HandlerAdapter & Argument Resolution: Startup-time mapping metadata construction, HandlerAdapter invocation, method argument resolution (@PathVariable, @RequestParam, @RequestBody), and Jackson HttpMessageConverter.

Module 19: Manual Spring MVC, JSP & Spring Boot Auto-Config

• 19.1 Manual Spring MVC & Embedded Tomcat Bootstrap: Manual dependency triad (spring-webmvc, tomcat-embed-core, jackson-databind), @EnableWebMvc setup, AnnotationConfigWebApplicationContext, DispatcherServlet registration, and App.java blueprint.
• 19.2 ViewResolver, JSP Pipeline & Spring Boot Automation: InternalResourceViewResolver, JSP pipeline, WEB-INF security boundary, Spring Boot auto-configuration, and in-memory HashMap vs database complexity.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

Module 14: Soft Delete Architecture & JPA Filtering

• 14.1 Logical Deletion Semantics & Entity Mapping: Hard delete (DELETE) vs Soft delete (PATCH /soft-delete), archive cabinet analogy, physical existence vs application visibility, @Column(name = "is_deleted"), and state machine transitions.
• 14.2 Derived Query Methods & The findById Trap: The findAll() and findById() data leakage traps, derived query syntax (findByIsDeletedFalse, findByIdAndIsDeletedFalse), and 3-step soft delete execution pipeline.

Module 15: Soft Delete Production Patterns & Indexing

• 15.1 Controller-Service Pipeline & PATCH Semantics: REST @PatchMapping("/{id}/soft-delete") controller boundary, @Transactional service state mutations, complete reference code implementation, and end-to-end mental model.
• 15.2 Indexing, Anti-Patterns & Refactoring: Database indexing caveats for low-cardinality boolean flags, composite index solutions, operational query complexity matrix, 7 production pitfalls, and API refactoring.

Module 16: Servlets Architecture & Container Lifecycle

• 16.1 Servlets Fundamentals & Restaurant Analogy: Java Servlets fundamentals, Restaurant Kitchen mental model, why raw ServerSocket is insufficient, static vs dynamic sites, and Servlet container IoC.
• 16.2 Servlet Lifecycle, Concurrency & Request Pipeline: Complete 4-phase lifecycle pipeline (init, service, destroy), single-instance multithreaded concurrency hazards, and HttpServletRequest/HttpServletResponse abstractions.

Module 17: Servlet Deployment & Spring MVC Progression

• 17.1 WAR Packaging, Provided Scope & Embedded Tomcat: Web Application Archive (.war) structure, Maven <scope>provided</scope> classloader isolation rule, external Tomcat administration, and Spring Boot embedded container model.
• 17.2 DispatcherServlet, Spring MVC & Production Pitfalls: Traditional Servlet scaling bottlenecks, DispatcherServlet Front Controller pattern, 6-stage architectural progression, production pitfalls matrix, and debugging challenges.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

Module 14: Soft Delete Architecture & JPA Filtering

• 14.1 Logical Deletion Semantics & Entity Mapping: Hard delete (DELETE) vs Soft delete (PATCH /soft-delete), archive cabinet analogy, physical existence vs application visibility, @Column(name = "is_deleted"), and state machine transitions.
• 14.2 Derived Query Methods & The findById Trap: The findAll() and findById() data leakage traps, derived query syntax (findByIsDeletedFalse, findByIdAndIsDeletedFalse), and 3-step soft delete execution pipeline.

Module 15: Soft Delete Production Patterns & Indexing

• 15.1 Controller-Service Pipeline & PATCH Semantics: REST @PatchMapping("/{id}/soft-delete") controller boundary, @Transactional service state mutations, complete reference code implementation, and end-to-end mental model.
• 15.2 Indexing, Anti-Patterns & Refactoring: Database indexing caveats for low-cardinality boolean flags, composite index solutions, operational query complexity matrix, 7 production pitfalls, and API refactoring.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

Module 12: Spring Data JPA, ORM & Repository Engineering

• 12.1 ORM, Hibernate Mechanics & DataSource Configuration: Restaurant analogy table, Object-Relational Impedance Mismatch, JPA vs Hibernate, JDBC URL breakdown, ddl-auto setting matrix, and Flyway/Liquibase schema migrations.
• 12.2 Entity Design, Repository Proxies & Persistence Context: @Entity mapping blueprint, JDK dynamic proxies for repository interfaces, Persistence Context dirty checking mechanics, B-Tree index lookup complexity $O(\log_B N)$, and findAll() heap memory traps vs Pageable.

Module 13: Advanced REST Controllers, DTOs & Production Architecture

• 13.1 REST Controllers, ResponseEntity & Jackson: @RestController protocol boundary, ResponseEntity<T> structure, standard CRUD HTTP status codes, Jackson serialization pipeline, clean Optional<T> handling, and 11-step execution sequence.
• 13.2 DTOs, State Machines, Anti-Patterns & Debugging: DTO records vs Entity over-posting risks, Mermaid entity state machine, TOCTOU race conditions, 5 production anti-patterns, and outside-in debugging checklists.

---

Module 1: Foundations & Architecture

• 1.1 Client-Server & HTTP Protocol: Web communication primitives, IP addressing, ports, sockets, URL anatomy, HTTP methods (GET, POST, PUT, PATCH, DELETE), headers, status codes, and idempotency rules.
• 1.2 Servlets & Servlet Containers: Low-level ServerSocket handling vs Servlet translation API (HttpServlet), Tomcat container mechanics, thread-per-request execution model, and concurrency safety.
• 1.3 Spring Ecosystem & Boot Overview: Historical evolution from EJB 2.x to Spring, Framework vs Boot distinction, Spring ecosystem stack layers, opinionated defaults, embedded server execution model, and microservices alignment.

Module 2: Build Tooling & Application Setup

• 2.1 Maven Build Engineering: Apache Maven build pipeline, pom.xml architecture, GAV coordinates, SNAPSHOT vs Release semantics, transitive dependency resolution, local .m2 caching, and spring-boot-maven-plugin Fat JAR repackaging.
• 2.2 Bootstrap & First Controller: Spring Initializr, canonical project layout, @SpringBootApplication meta-annotation breakdown, @RestController, request routing, application properties, request lifecycle, and step-by-step 404/startup debugging.

Module 3: Spring Core — IoC & Dependency Injection

• 3.1 Inversion of Control & Dependency Injection: Tight vs loose coupling, interface abstraction, IoC container principles, Constructor vs Field vs Setter injection styles, SRP/OCP alignment, and unit testing mockability.
• 3.2 Spring Beans & Component Scanning: ApplicationContext vs BeanFactory, Stereotype annotations (@Component, @Service, @Repository), @ComponentScan boundaries, explicit Java config (@Configuration & @Bean), BeanDefinition metadata, and resolving bean ambiguity with @Primary and @Qualifier.

Module 4: Bean Lifecycle & Advanced Container Mechanics

• 4.1 Spring Bean Lifecycle & Hooks: Complete 10-stage container execution pipeline from scanning and instantiation to BeanPostProcessor interception, AOP proxy wrapping, @PostConstruct, and @PreDestroy resource cleanup.
• 4.2 Bean Scopes, Lazy Initialization & Circular Dependencies: Core (singleton, prototype) and web scopes (request, session), resolving the prototype-in-singleton injection problem via ObjectProvider, @Lazy proxies, circular dependency deadlock mechanics, and refactoring strategies.

Module 5: Legacy Configuration & Hybrid Interop

• 5.1 Legacy XML Configuration & Hybrid Interop: Legacy XML blueprints (beans.xml), <bean> declarations, value vs ref wiring, collection injection, XML autowiring modes, custom lifecycle hooks (init-method, destroy-method), and hybrid integration via @ImportResource.

Module 6: Spring Boot Annotations & Bootstrap

• 6.1 Startup Mechanics & SpringApplication.run(): Spring Core vs Spring Boot startup, SpringApplication.run() execution stages, ApplicationContext creation, DI vs Service Locator patterns, and CommandLineRunner.
• 6.2 @SpringBootApplication & Component Scanning: @SpringBootApplication composite meta-annotation breakdown (@SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan), annotation taxonomy matrix, and root package scanning rules.

Module 7: Auto-Configuration & Conditional Mechanics

• 7.1 Auto-Configuration & Classpath Signals: @ComponentScan vs @EnableAutoConfiguration, automated workshop mental model, auto-configuration decision pipeline, starters as signals, and console vs web app auto-detection.
• 7.2 Conditional Beans & Production Diagnostics: @ConditionalOnClass, @ConditionalOnMissingBean, developer vs auto-configured bean precedence, full startup state machine, 5 production debugging questions, and anti-patterns.

Module 8: Externalized Configuration & Property Binding

• 8.1 Configuration Sources, Properties & YAML: Code vs Config boundary, application.properties vs application.yml, packaged resources vs true externalized configuration, OS environment variables, and environment-specific settings.
• 8.2 @Value vs @ConfigurationProperties & Relaxed Binding: Single property resolution via @Value, default value syntax (${key:default}), @ConfigurationProperties grouped binding, relaxed binding mechanics (kebab-case to camelCase), and trade-off matrices.

Module 9: Runner Interfaces & Startup Pipeline

• 9.1 CommandLineRunner vs ApplicationRunner: Non-web startup tasks vs HTTP controllers, manual bean lookup anti-patterns, raw String... args vs structured ApplicationArguments (--key=value option flags).
• 9.2 End-to-End Configuration Pipeline & Pitfalls: Complete Spring Boot startup data flow (Mermaid sequence), configuration-to-bean execution pipeline, production pitfalls, end-to-end code example, and self-assessment challenges.

Module 10: Layered Architecture & JPA Persistence

• 10.1 Layered Architecture & Responsibilities: Restaurant kitchen analogy, Controller-Service-Repository separation, God Controller anti-pattern, package layout, @SpringBootApplication component scanning, and MySQL Server vs Client vs Workbench tooling.
• 10.2 JPA Entities, ORM & Database Auto-Configuration: Entity vs flow layer mental model, @Entity mapping, ORM object-to-row transformation, dependency stack, and why adding database starters without properties causes startup crashes.

Module 11: REST CRUD Implementation & Production Patterns

• 11.1 REST Mapping & CRUD Operations: REST endpoint matrix, @PathVariable vs @RequestBody, step-by-step Create/Read/Update implementations, 3-step update workflow, and 10-step request execution pipeline.
• 11.2 Hard vs Soft Delete, Pitfalls & Refactoring: Hard delete vs soft delete (isDeleted flag), entity state transition model, database operation complexity matrix, 5 production pitfalls, and God Controller refactoring.

---

⚡ Quick Reference & Comparison Matrices

1. Spring Framework vs. Spring Boot Comparison

---

2. Spring Ecosystem Stack Layers

---

❓ Self-Assessment Knowledge Check

---

🚀 Get Started

Begin your journey with Module 1.1: Client-Server & HTTP Protocol to master client-server communication, networking primitives, HTTP protocols, and request execution mechanics!