MVC Design Pattern in Java

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MVC Design Pattern in Java with Examples

In this article, I am going to discuss the MVC Design Pattern in Java with Examples. Please read our previous article where we discussed the Visitor Design Pattern in Java with Examples. In this article, we will explore the MVC Design Pattern in Java, its advantages, disadvantages, and practical applications in modern software development.

What is MVC Design Pattern?

MVC is an architectural software design pattern that is used for developing interactive applications where their user interaction is involved and based on the user interaction some event handling has occurred. It is not only used for web-based applications but it can also be used for Desktop or mobile-based applications where there are user interactions involved.

MVC stands for Model View and Controller. It is an architectural design pattern which means this design pattern is used at the architecture level of an application. So, the point that you need to remember is MVC is not a programming language, MVC is not a Framework, it is a design pattern. When we design an application, first we create the architecture of that application, and MVC plays an important role in the architecture of that particular application.

In the world of software development, managing the complexity of applications is crucial to ensure maintainability and scalability. The Model-View-Controller (MVC) design pattern has emerged as a powerful solution for separating concerns, enhancing code organization, and promoting reusable and maintainable software.

The Model-View-Controller (MVC) design pattern divides an application into three interconnected components: the Model, the View, and the Controller. Each component has distinct responsibilities and interactions, leading to a separation of concerns and a clear division of responsibilities.

• Model: The Model represents the data and the business logic of the application. It encapsulates the state and behavior of the application and provides an interface to manipulate and access the data. The Model is independent of the user interface and does not depend on how the data is presented or interacted with.
• View: The View represents the user interface of the application. It is responsible for presenting the data from the Model to the user and capturing user interactions. The View observes the Model for any changes and updates itself accordingly. It should ideally be passive and not contain any business logic.
• Controller: The Controller acts as an intermediary between the Model and the View. It receives user input from the View, interprets it, and initiates appropriate actions on the Model. It is responsible for coordinating the flow of data between the Model and the View, ensuring that they remain synchronized.

MVC design pattern was introduced in the 1970s that basically divides an application into 3 major components as Model, View, and Controller. The main objective of the MVC design pattern is the separation of concerns (codes), which means the domain model and business logic are separated from the user interface (i.e. view). As a result, maintenance and testing of the application become simpler and easier.

Example to Understand MVC Design Pattern in Java

A real-world example where the MVC Design Pattern can be used is in employee data storage applications. Consider a system that allows users to view all the employees of a company. The MVC design pattern can effectively structure the application and separate its various components. The Controller acts as the intermediary between the Model and the View. It handles user interactions and translates them into actions on the Model.

By utilizing the MVC Design Pattern, the application benefits from a clear separation of concerns. Changes to the user interface, such as updating the design or adding new features, can be implemented in the View component without affecting the underlying business logic in the Model. Likewise, modifications to the data handling or business rules can be made in the Model without impacting the user interface. The Controller ensures smooth communication and synchronization between the Model and the View, maintaining consistency and integrity throughout the application.

Overall, the MVC design pattern proves valuable in development by providing a structured approach that separates data, presentation, and user interactions. It promotes code reusability, maintainability, and scalability, allowing developers to efficiently build and evolve complex web applications with ease. The UML Diagram of this example is given below using MVC Design Pattern.

Step 1: Create a new directory to store all the class files of this project.

Step 2: Open VS Code and create a new project, called MVC.

Step 3: In the project, create a new file called Employee.java. Add the following code to the file:

public class Employee
{
    private int id;
    private String name, email;

    public int getId()                  {return id;}
    public void setId(int id)           {this.id = id;}
    public String getName()             {return name;}
    public void setName(String name)    {this.name = name;}
    public String getEmail()            {return email;}
    public void setEmail(String email)  {this.email = email;}

    public Employee(int id, String name, String email) {
        this.id = id;
        this.name = name;
        this.email = email;
    }
}

To implement the setters, getters, and constructor, you may use the “Source Action…” method found in the right-click menu of VS Code. Other IDEs usually have some similar option to automatically generate setters, getters, and constructors.

Step 4: In the project, create a new file called EmployeeView.java. This class is responsible for displaying the employee data. Add the following code to EmployeeView.java:

public class EmployeeView
{
    public void printEmployeeDetails(Employee e)
    {
        System.out.println("Employee no: " + e.getId());
        System.out.println("Name: " + e.getName());
        System.out.println("Email: " + e.getEmail());
    }    
}

Step 5: In the project, create a new file called EmployeeController.java. This class is responsible for the communication between the main class, the Employee class, and the EmployeeView class. Add the following code to EmployeeController.java:

public class EmployeeController
{
    private Employee e;
    private EmployeeView ev;

    public EmployeeController(Employee e, EmployeeView ev)
    {
        this.e = e;
        this.ev = ev;
    }
    
    public void setEmployeeName (String name)   {e.setName(name);}
    public void setEmployeeEmail (String email) {e.setEmail(email);}
    public void setEmployeeId (int id)          {e.setId(id);}

    public String getEmployeeName ()    {return e.getName();}
    public String getEmployeeEmail ()   {return e.getEmail();}
    public int getEmployeeId ()         {return e.getId();}

    public void view()  {ev.printEmployeeDetails(e);}
}

Step 6: In the project, create a new file called MVCPatternDemo.java. This class will contain the main() function. Add the following code to MVCPatternDemo.java:

public class MVCPatternDemo
{
    public static void main(String[] args)
    {
        EmployeeController ec = new EmployeeController(retreiveEmployee(), new EmployeeView());
        ec.view();
        ec.setEmployeeName("Employee B");
        ec.setEmployeeEmail("employee.b@company.com");
        ec.view();
    }

    private static Employee retreiveEmployee()
    {return new Employee(1, "Employee A", "employee.a@company.com");}
}

The main() function creates an object of the type EmployeeController and initializes it with a new employee and a new object of the type EmployeeView. It displays the employee’s data. Then, it modifies the data of the employee in the controller. Finally, it displays the employee’s data again.

Step 7: Compile and execute the application. Ensure compilation is successful. Verify that the program works as expected.

Congratulations! You now know how to implement MVC patterns!

UML Diagram of MVC Design Pattern:

Now, let us see the MVC Design Pattern UML Diagram Components with our Example so that you can easily understand the UML Diagram.

The classes can be described as follows:

1. Object: This is the POJO class.
2. ObjectView: This class is responsible for displaying the data of the Object.
3. ObjectController: This class is responsible for communication between DriverClass, Object, and ObjectView.
4. DriverClass: This class contains the main() function and is responsible for the simulation of the program.

Advantages of MVC Design Pattern in Java:

The followings are the advantages of using the MVC Design Pattern in Java:

• Separation of Concerns: The MVC design pattern provides a clear separation of concerns, ensuring that each component focuses on its specific responsibility. This separation enhances code organization, readability, and maintainability. Changes made to one component, such as the Model, have minimal impact on the other components, allowing for easier code updates and debugging.
• Code Reusability: The MVC design pattern promotes code reusability by encapsulating functionality within distinct components. The Model can be reused in different contexts without modification, providing consistent data manipulation and business logic. Similarly, multiple Views can be created to present the same data in different ways, allowing for flexibility and customization.
• Testability: The MVC design pattern enhances testability by decoupling the components. The Model can be tested independently using unit tests, ensuring that the business logic functions correctly. The View can be tested for proper rendering and display of data, while the Controller can be tested for its interaction with the Model and View.
• Scalability and Maintainability: The separation of concerns offered by the MVC design pattern simplifies scalability and maintainability. As the application grows, each component can be extended or modified independently without impacting the others. This modularity allows for easier maintenance and the addition of new features or functionality.
• Flexibility and Adaptability: The MVC design pattern provides flexibility and adaptability to changing requirements. With a clear separation between the Model, View, and Controller, it becomes easier to modify or replace one component without affecting the others. This allows for easy updates, migrations to new technologies, or the introduction of new user interfaces.

Disadvantages of MVC Design Pattern in Java:

The followings are the disadvantages of using the MVC Design Pattern in Java:

• Complexity: Implementing the MVC design pattern can introduce additional complexity to the application architecture. The separation of concerns and the interconnections between the components may require a higher level of understanding and design effort. Developers need to ensure proper communication and synchronization between the Model, View, and Controller, which can be challenging for large-scale applications.
• Learning Curve: The MVC design pattern may have a steep learning curve, especially for developers who are new to it. Understanding the responsibilities and interactions of the Model, View, and Controller requires a solid grasp of the design pattern’s principles and best practices. Adequate training and documentation can help overcome this challenge.
• Overhead: The MVC design pattern may introduce some overhead due to the need for inter-component communication and synchronization. As the application grows, managing the data flow and keeping the components in sync can become more complex, potentially impacting performance. However, this can be mitigated through proper design and optimization techniques.
• Lack of Standardization: The MVC design pattern does not have a universally standardized implementation. Different frameworks and libraries may interpret and implement MVC in slightly different ways, leading to inconsistencies in terminology, structure, or component interactions. Developers working with multiple frameworks or legacy codebases may need to adapt to these variations.

In the next article, I am going to discuss Business Delegate Design Pattern in Java with Examples. Here, in this article, I try to explain MVC Design Pattern in Java with Examples. I hope you understood the need for and use of the MVC Design Pattern in Java.