CircleMVC — Java Back-End Project Built with Maven

📘 Project Description

This is a Java Back-End project built with Maven, following the Model-View-Controller (MVC) design pattern.
The goal of the project is to create a simple Circle class that can calculate and store geometric data (area and perimeter) based on a given radius.

Later, the project will include a SQL database to store all circle data entered via the keyboard.
Each entry will record:

• The radius
• The calculated perimeter
• The calculated area

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Table of contents

• Understanding process MVC

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🧮 1. Features

• Input a circle’s radius.
• Compute the area and perimeter.
• Display results through the console view.
• Future feature: Store results in a SQL database.

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🏗️ 2. Architecture. Explanation of the MVC Pattern

The project follows the MVC (Model-View-Controller) pattern:

• Model: Represents the data and business logic (e.g., the Circle class).
• View: Handles user interaction (e.g., console input/output).
• Controller: Coordinates communication between the Model and the View.

┌────────────┐       ┌─────────────┐       ┌────────────┐
│   View     │ <---> │ Controller  │ <---> │   Model    │
└────────────┘       └─────────────┘       └────────────┘

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Layer	Role	Class
Model	Represents the data and business logic	Circle.java
View	Handles user interaction (input/output)	CircleView.java
Controller	Coordinates interaction between model and view	CircleController.java

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📦 3. Project Structure

java-mvc-circle/
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/example/circle/
│   │   │       ├── model/
│   │   │       │   └── Circle.java
│   │   │       ├── view/
│   │   │       │   └── CircleView.java
│   │   │       └── controller/
│   │   │           └── CircleController.java
│   │   └── resources/
│   └── test/
│       └── java/
│           └── com/example/circle/
│               └── CircleTest.java
├── pom.xml
└── README.md

🧭 4. UML Diagram in Mermaid Format

classDiagram
    direction TB

    class Circle {
        - double radius
        + Circle(double radius)
        + getRadius() double
        + setRadius(double radius)
        + calculatePerimeter() double
        + calculateArea() double
        + toString() String
    }

    class CircleView {
        - Scanner scanner
        + CircleView()
        + requestRadius() double
        + displayResults(perimeter double, area double) void
        + displayMessage(message String) void
    }

    class CircleController {
        - CircleView view
        + CircleController(view CircleView)
        + start() void
    }

    CircleController --> CircleView : uses
    CircleController --> Circle : creates/manages

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🧭 4.1. Full UML Diagram (Model-View-Controller)

┌────────────────────────────┐
│        Circle              │  <<Model>>
├────────────────────────────┤
│ - radius: double           │
├────────────────────────────┤
│ + Circle(radius: double)   │
│ + getRadius(): double      │
│ + setRadius(radius: double)│
│ + calculatePerimeter(): double │
│ + calculateArea(): double  │
│ + toString(): String       │
└────────────────────────────┘

             ▲
             │ uses
             │
┌────────────────────────────┐
│       CircleController     │  <<Controller>>
├────────────────────────────┤
│ - view: CircleView         │
├────────────────────────────┤
│ + CircleController(v: CircleView) │
│ + start(): void            │
└────────────────────────────┘
             │
             │ calls
             ▼
┌────────────────────────────┐
│        CircleView          │  <<View>>
├────────────────────────────┤
│ - scanner: Scanner         │
├────────────────────────────┤
│ + CircleView()             │
│ + requestRadius(): double  │
│ + displayResults(p: double, a: double): void │
│ + displayMessage(msg: String): void          │
└────────────────────────────┘

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💻 5. Base Code for Each Class

🧱 Model: Circle.java

package com.teoria.circulo.model;

public class Circle {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    public double getRadius() {
        return radius;
    }

    public void setRadius(double radius) {
        this.radius = radius;
    }

    public double calculatePerimeter() {
        return 2 * Math.PI * radius;
    }

    public double calculateArea() {
        return Math.PI * Math.pow(radius, 2);
    }

    @Override
    public String toString() {
        return "Circle [radius=" + radius + 
               ", perimeter=" + calculatePerimeter() + 
               ", area=" + calculateArea() + "]";
    }
}

🎨 View: CircleView.java

package com.teoria.circulo.view;

import java.util.Scanner;

public class CircleView {
    private Scanner scanner;

    public CircleView() {
        scanner = new Scanner(System.in);
    }

    public double requestRadius() {
        System.out.print("Enter the circle's radius: ");
        return scanner.nextDouble();
    }

    public void displayResults(double perimeter, double area) {
        System.out.printf("Perimeter: %.2f%n", perimeter);
        System.out.printf("Area: %.2f%n", area);
    }

    public void displayMessage(String message) {
        System.out.println(message);
    }
}

🧭 Controller: CircleController.java

package com.teoria.circulo.controller;

import com.teoria.circulo.model.Circle;
import com.teoria.circulo.view.CircleView;

public class CircleController {
    private CircleView view;

    public CircleController(CircleView view) {
        this.view = view;
    }

    public void start() {
        double radius = view.requestRadius();
        Circle circle = new Circle(radius);

        double perimeter = circle.calculatePerimeter();
        double area = circle.calculateArea();

        view.displayResults(perimeter, area);

        // Later: save to database
        // saveToDB(circle);
    }
}

🚀 Main Class

package com.teoria.circulo;

import com.teoria.circulo.view.CircleView;
import com.teoria.circulo.controller.CircleController;

public class Main {
    public static void main(String[] args) {
        CircleView view = new CircleView();
        CircleController controller = new CircleController(view);
        controller.start();
    }
}

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🧩 6. Future Expansion: SQL Database Connection

Later, the project will add:

• A CircleDAO class (in model.dao) to handle CRUD operations with SQL.
• A circles table in the database with columns:

CREATE TABLE circles (
    id INT AUTO_INCREMENT PRIMARY KEY,
    radius DOUBLE,
    perimeter DOUBLE,
    area DOUBLE
);

• The controller will call CircleDAO.insert(circle) after calculating results.

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⚙️ 7. Requirements

• Java 17 or later
• Maven 3.8+
• (Optional later) MySQL or PostgreSQL for data persistence

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🚀 8. How to Run the Project

1. Clone this repository:

   git clone https://github.com/alexpjava/java-mvc-circle.git
   cd java-mvc-circle

2. Build the project with Maven:

   mvn clean install

3. Run the application:

   mvn exec:java -Dexec.mainClass="com.example.circle.Main"

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🧠 9. Future Improvements

• Add SQL database integration to store circle data.
• Add unit tests with JUnit.
• Add a graphical user interface (optional).
• Generate and include the UML diagram.

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📄 10. License

This project is open-source and available under the MIT License.

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✍️ 11. Author

AlexP
GitHub: @alexpjava
Email: alexp.java@gmail.com