Advanced Spring Framework Guide

Welcome to the Advanced Spring Framework repository — a curated reference and visual guide for mastering Spring's most powerful and enterprise-grade features.

This repo is ideal for:

• Senior Java developers
• Tech Leads
• Architects building enterprise Spring applications
• Engineers transitioning into microservices or cloud-native development

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What You'll Find Here

This repository is structured by Spring modules and includes:

• ✅ Hands-on code examples (Java 21, Spring Boot 3+)
• ✅ Visual Mermaid diagrams to explain architecture, flow, and lifecycles
• ✅ Explanations for real-world use cases, not just Hello World
• ✅ Design patterns and anti-patterns

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Resource	Description
Mermaid Docs	Visual flowcharts and architecture graphs

📂 Project Structure

├── core/
│   ├── bean_lifecycle/
│   └── custom_post_processors/
│
├── aop/
│   ├── logging_aspect/
│   └── security_aspect/
│
├── transactions/
│   ├── propagation_isolation/
│   └── nested_transactions/
│
├── security/
│   ├── jwt_auth/
│   └── method_level_security/
│
├── events/
│   ├── sync_async_events/
│   └── domain_events/
│
├── data/
│   ├── spring_data_jpa/
│   └── querydsl_specifications/
│
├── cloud/
│   ├── service_discovery/
│   └── config_server/

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🧠 Key Concepts Covered

Topic	Highlights
Spring Core	Bean lifecycle, scopes, post processors
Spring AOP	Custom aspects, join points, @Around logic
Transaction Mgmt	Propagation, isolation, rollback strategy
Spring Security	JWT authentication, filters, RBAC
Event System	Decoupled communication with sync/async events
Spring Data	Repositories, projections, specifications
Spring Cloud	Config Server, Eureka, Resilience4j

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🔁 Example: Spring Security with JWT

graph TD
    subgraph Client
        A[User Login Request] --> B[POST /auth/login]
    end

    subgraph Backend API
        B --> C[AuthenticationFilter]
        C --> D[AuthenticationManager]
        D --> E[UserDetailsService + JWTProvider]
        E --> F[JWT Token Response]
    end

    F --> A

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