🗒️ Java Notes App — Layered Architecture

Demo

⚙️ Dependencies Used

• Spring Web
• Spring DevTools
• Thymeleaf
• MySQL Driver
• Spring Data JPA

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🧩 Architecture Overview

A Java Notes App implemented using a Layered Architecture:

Layers

Layer	Description
Presentation Layer	Handles HTTP requests → Controllers
Service Layer	Coordinates calls between layers
Repository Layer	Interfaces with the database via JPA (CRUD only)

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🗂️ Project Structure

com.example.notesapp
├── controller    → Handles HTTP requests
├── service       → Business logic
├── repository    → Database access (JPA)
├── model         → Entity classes

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🧭 Development Plan

1️⃣ Define the Data Entity

Create the Note entity class using JPA annotations to map it to your database table.

Example fields:

long id;
String title;
String content;
boolean isPinned;
LocalDateTime createdAt;
LocalDateTime updatedAt;

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2️⃣ Set Up the MySQL Database

• Create a new MySQL database schema for storing notes data.

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3️⃣ Configure Spring Boot to Connect to MySQL

Add connection properties to your application.properties or application.yml:

spring.datasource.url=jdbc:mysql://localhost:3306/notesdb
spring.datasource.username=root
spring.datasource.password=yourpassword
spring.jpa.hibernate.ddl-auto=update

Make sure the MySQL driver dependency is included.

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4️⃣ Create the Repository Interface

Define an interface to handle CRUD operations:

public interface NoteRepository extends JpaRepository<NoteEntity, Long> {}

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5️⃣ Run the Application

When you run your Spring Boot app, JPA/Hibernate will automatically generate the notes table based on your entity class.

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🧱 What is an Entity?

An Entity is a Java class representing a database table.
Each instance of the entity corresponds to one row in that table.

Example:

Field	Type	Description
id	long	Primary key
title	String	Note title
content	String	Note content
createdAt	LocalDateTime	Creation timestamp
updatedAt	LocalDateTime	Last update timestamp
isPinned	boolean	Whether the note is pinned

updatedAt and isPinned help with sorting and prioritizing notes.

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🧰 What is the Repository Interface?

An abstraction layer for performing CRUD operations on entities.
It allows you to access and manipulate data without writing SQL directly.

Example:

public interface NoteRepository extends JpaRepository<NoteEntity, Long> {}

The CRUDService class uses this repository to interact with the database.

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🎯 What is the Controller?

The Controller is the entry point for HTTP requests — it connects the frontend with your backend.

Responsibilities:

• Accepts requests (GET, POST, PUT, DELETE)
• Maps them to Java methods
• Interacts with the service layer
• Returns HTML views or JSON responses

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