https://github.com/avidee007/spring-modulith-library-app

Library management app built using spring modulith project with spring boot.
https://github.com/avidee007/spring-modulith-library-app

domain-driven-design modular modules spring-modulith

Last synced: 11 months ago
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Library management app built using spring modulith project with spring boot.

• Host: GitHub
• URL: https://github.com/avidee007/spring-modulith-library-app
• Owner: avidee007
• Created: 2025-08-04T16:20:23.000Z (11 months ago)
• Default Branch: main
• Last Pushed: 2025-08-06T15:30:58.000Z (11 months ago)
• Last Synced: 2025-08-06T17:28:09.111Z (11 months ago)
• Topics: domain-driven-design, modular, modules, spring-modulith
• Language: Java
• Homepage:
• Size: 71.3 KB
• Stars: 0
• Watchers: 0
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

          
# 📚 Spring-Modulith Library App

**Modular Monolith Library Management System**  

Built using Spring Boot, Spring Modulith & Domain‑Driven Design  

Domains: **Rental**, **Inventory**, **Notifications**

---

## Introduction

This repository contains a **sample Library Management System** built with **Spring Modulith**. It demonstrates how to structure a Spring Boot application into **modular components** with **clearly defined context boundaries**, adhering to **Domain-Driven Design (DDD)** principles.

![components.svg](docs/components.svg)

## Key characteristics of this architecture:

- **Modular Design** – Each module encapsulates its own domain logic and data.

- **Inter‑module Communication** – Modules interact either **synchronously** via exposed APIs or **asynchronously** using domain events.

- **Loose Coupling** – Reduces dependencies between modules, improving maintainability and scalability.

- **Microservice‑ready** – Clear boundaries simplify transitioning from a monolithic architecture to distributed **microservices** as the system evolves.

---

## 🔦 Why Spring Modulith?

- **Modular Monolith Architecture**: Encapsulate functional domains into modules (rental, inventory, notifications), improving maintainability and clarity.

- **Structural Verification**: Enforce module boundaries using `ApplicationModules.of(...).verify()` in tests, preventing illegal package dependencies.

- **Event‑Driven Communication**: Modules interact via domain events instead of direct service injection, leading to loose coupling and high cohesion.

- **Self‑Documenting Modules**: Automatically generate module documentation diagrams and artifacts via Spring Modulith tooling. [module-docs](docs)

---

## ⚙️ Workflow Overview

1. **Rental API Call**

    - `POST /api/rentals/rent` → RentalService persists rental and publishes `RentalEvent`.

   

    - `POST /api/rentals/return` → RentalService updates rental with return date time and publishes `ReturnEvent`.

2. **Inventory Listener**

    - Consumes `RentalEvent` → decrements available copies and publishes `RentalSuccessEvent`

    - Consumes `ReturnEvent` → increments available copies and publishes `ReturnSuccessEvent`.

3. **Notifications Listener**

    - Listens to both `RentalSuccessEvent` and `ReturnSuccessEvent` events and logs notification metadata (bookId, userId, timestamps).

---

## 📦 Key Features

- **Events driven side effects**: inventory updates and notifications handled asynchronously.

- **Modular isolation**: each domain encapsulates its own model and logic.

- **Automated architecture enforcement**: `module verify` tests catch coupling violations.

---

## 🧭 Benefits in Real–World Development

1. **Clean Domain Separation** – Each module owns its model and operations.

2. **Evolution‑Friendly Architecture** – Easy to add new modules or external integrations (e.g., Kafka, Email).

3. **Independent Testing** – Modules can be tested individually using @ApplicationModuleTests.

4. **Microservice Migration Ready** – Event-driven design simplifies extraction into microservices if needed.

## 🧪 Getting Started

### Prerequisites

- Java 17+

- Gradle (wrapper included) or Maven

- Postgres Database

### Clone & Run

```

git clone https://github.com/avidee007/spring-modulith-library-app.git

cd spring-modulith-library-app 

```

#### Build application

```bash

  ./gradlew build

```

#### Run application

```bash

  ./gradlew bootRun

```

#### Run tests

```bash

  ./gradlew test

```