Library Management System Microservices

A collection of Spring Boot microservices implementing a library management system, featuring:

• Gateway Service: API gateway for routing and authentication.
• Auth Service: OAuth2 authorization server, user registration, login, JWT issuance.
• User Service: Manages user profiles (CRUD) with role-based access control.
• Book Service: Manages book catalog (CRUD) on MongoDB.
• Borrow Service: Handles borrowing & returning books.
• Notification Service: Sends due-date reminders.

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Architecture Diagram

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Services Overview

0. Service Discovery (discovery-service)

• Type: Netflix Eureka Server
• Port: 8761
• Responsibilities:
  • Maintains registry of all microservices
  • Enables dynamic service discovery for Gateway and inter-service calls
• Configuration:
  • Annotated with @EnableEurekaServer
  • Services register via spring.cloud.discovery.client.* settings

1. Gateway Service (gateway-service)

• Type: Spring Cloud Gateway (Reactive)
• Port: 2222
• Responsibilities:
  • Routes requests to backend services using service IDs
  • Validates JWTs via .well-known/jwks.json
  • Integrates with Eureka for dynamic routing

2. Authentication Service (auth-service)

• Type: Spring Authorization Server
• Port: 8070
• Responsibilities:
  • OAuth2 endpoints: /oauth2/authorize, /oauth2/token
  • User registration (/auth/register), login (/auth/login), token refresh
  • Role & permission management (ADMIN, ATTENDANT, USER)
• Security:
  • RSA-signed JWTs (RS256)
  • JWKS endpoint: /.well-known/jwks.json
  • Method security via @EnableMethodSecurity and @PreAuthorize

3. User Service (user-service)

• Type: Spring Boot MVC + JPA
• Port: 8081
• Database: PostgreSQL (UUID primary keys)
• Responsibilities:
  • CRUD operations on users
  • Profile updates, password change (with current-password verification)
• Security:
  • JWT resource server configuration with NimbusJwtDecoder
  • Method-level security via @PreAuthorize
  • Authorities extracted from JWT roles claim

4. Book Service (book-service)

• Type: Spring Boot MVC + Spring Data MongoDB
• Port: 8082
• Database: MongoDB
• Responsibilities:
  • CRUD operations on books
  • Maintain availability counts
• Security:
  • JWT resource server
  • Protected endpoints via @PreAuthorize (e.g., hasAuthority('USER_BORROW_BOOK'))

5. Borrow Service (borrow-service)

• Type: Spring Boot MVC + JPA
• Port: 8083
• Database: PostgreSQL
• Responsibilities:
  • Handle borrow/return requests
  • Update book availability via events or REST calls
• Security:
  • JWT resource server
  • Role-based approval: ATTENDANT approves borrow requests

6. Notification Service (notification-service)

• Type: Spring Boot MVC + Scheduler
• Responsibilities:
  • Schedule and send reminders for due dates
  • Integrate with email/SMS provider

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Inter-Service Communication

• Event-Driven: Services publish domain events (e.g., BookBorrowed) on a message broker for eventual consistency.
• Synchronous REST: Services verify availability or user details via REST calls when immediate consistency is required.

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Security & RBAC

• Roles:
  • ROLE_ADMIN: full system access
  • ROLE_ATTENDANT: manage borrowing, fines, inventory
  • ROLE_USER: view catalog, borrow/return books
• Permissions: granular authorities assigned per role (e.g., ADMIN_MANAGE_USERS, ATTENDANT_CHECKOUT_BOOK, USER_RATE_BOOK)
• JWT:
  • RS256-signed tokens
  • roles claim contains list of authorities
  • Gateway and resource servers use JWKS endpoint for key discovery

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Getting Started

Prerequisites

• Java 17+
• Maven 3.8+
• Docker & Docker Compose
• PostgreSQL
• MongoDB

Running Locally

1. Start databases:

    docker compose down && docker compose up -d