Front Controller Design Pattern in Java

Front Controller Design Pattern in Java

In this article, I am going to discuss Front Controller Design Pattern in Java with Examples. Please read our previous article where we discussed DAO Design Patterns in Java. In this article, we will explore the Front Controller Design Pattern in Java, its advantages, disadvantages, and practical applications in web development.

What is Front Controller Design Pattern?

In modern web application development, managing the flow of incoming requests and handling various actions can become complex. The Front Controller design pattern provides a structured approach to centralize request handling, improving code organization and promoting reusability.

The Front Controller design pattern is a software architectural pattern that aims to centralize request handling in a web application. It introduces a single-entry point called the Front Controller, which receives incoming requests and delegates them to appropriate handlers, known as Command Handlers or Actions. The Front Controller acts as a central coordinator, handling common tasks such as request routing, authentication, and error handling.

Components of Front Controller Design Pattern

The Front Controller Design Pattern consists of the following components:

  • Front Controller: It is responsible for receiving incoming requests, processing them, and dispatching them to the appropriate Command Handlers. The Front Controller provides a unified interface for handling requests and acts as a central point for request-handling logic.
  • Command Handlers: These are responsible for performing specific actions or processing specific requests. Each Command Handler is associated with a particular action or request type. The Command Handlers encapsulate the business logic and perform the necessary operations to fulfill the request.
  • Views: Views are responsible for rendering the response to the client. They present the processed data in an appropriate format, such as HTML, JSON, or XML. Views can be dynamically selected based on the request and the data processed by the Command Handlers.
Example to Understand Front Controller Design Pattern in Java

To understand the Front Controller design pattern in a real-world context, let’s consider a web application that handles user authentication and content management. The application uses the Front Controller pattern to centralize the request handling and provide a consistent flow for incoming requests.

In this scenario, the Front Controller acts as the main entry point for all requests coming into the application. It receives requests from the client and handles the initial processing, such as authentication, before dispatching the request to the appropriate Command Handler.

For example, when a user navigates to different pages or performs actions like logging in, creating a post, or updating profile information, the Front Controller determines the appropriate Command Handler based on the request URL or other parameters.

The Front Controller pattern allows for centralized authentication checks, error handling, and routing logic. It promotes code reusability, as the Command Handlers can be shared across different parts of the application that require similar functionality. Additionally, it simplifies the management and maintenance of the application by providing a clear separation of concerns.

By using the Front Controller Design Pattern, the web application achieves a structured and consistent request-handling flow, improving code organization, maintainability, and extensibility. It also enables the application to enforce security measures and perform common tasks consistently, enhancing overall performance and user experience. The UML Diagram of this example is given below using Front Controller Design Pattern.

Example to Understand Front Controller Design Pattern in Java

Implementing Front Controller Design Pattern in Java

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 frontcontroller.

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

public interface Page
{
    public void show();    
}

This is the interface that will be implemented by other concrete classes.

Step 4: Create two new files, called CustomerPage.java and EmployeePage.java. Both of these are concrete classes that implement the Page interface. Add the following code to the files:

CustomerPage.java
public class CustomerPage implements Page
{
    @Override
    public void show()
    {System.out.println("Welcome Customer!");}
}
EmployeePage.java
public class EmployeePage implements Page
{
    @Override
    public void show()
    {System.out.println("Welcome Employee!");}
}

Step 5: In the project, create a new file called Dispatcher.java. This class is responsible for dispatching the page. Add the following code to Dispatcher.java:

public class Dispatcher
{
    private Page custPage, empPage;
    
    public Dispatcher()
    {
        custPage = new CustomerPage();
        empPage = new EmployeePage();
    }

    public void dispatch(String type)
    {
        if (type.equalsIgnoreCase("employee"))
            empPage.show();
        else
            custPage.show();
    }
}

Step 6: In the project, create a new file called FrontController.java. This class will authenticate and issue the dispatch command to the dispatcher. Add the following code to FrontController.java:

public class FrontController
{
    private Dispatcher d;
    
    public FrontController()
    {d = new Dispatcher();}

    private boolean isValidUser()
    {
        System.out.println("User validated!");
        return true;
    }

    private void track (String request)
    {System.out.println("Requested page: " + request);}

    public void dispatchRequest (String request)
    {
        track(request);

        if (isValidUser())  d.dispatch(request);
    }
}

Step 7: In the project, create a new file called FrontControllerPatternDemo.java. This class will contain the main() function. Add the following code to FrontControllerPatternDemo.java:

public class FrontControllerPatternDemo
{
    public static void main(String[] args)
    {
        FrontController fc = new FrontController();
        fc.dispatchRequest("customer");
        fc.dispatchRequest("employee");
    }    
}

The main() function creates an object of type FrontController. It sends two dispatch requests, one for each page.

Step 8: Compile and execute the application. Ensure compilation is successful. Verify that the program works as expected.

Implementing Front Controller Design Pattern in Java

Congratulations! You now know how to implement Front Controller Design Pattern in Java!

UML Diagram of Front Controller Design Pattern:

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

UML Diagram of Front Controller Design Pattern

The classes can be described as follows:

  1. Object: This interface defines the functions that will be later implemented by the concrete object class.
  2. ConcreteObject: This class implements the functions defined in the aforementioned object interface.
  3. Dispatcher: This class is responsible for dispatching the object.
  4. FrontController: This class is responsible for the communication between the DriverClass and Dispatcher.
  5. DriverClass: This class contains the main() function and is responsible for the simulation of the program.
Advantages of Front Controller Design Pattern in Java:

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

  • Centralized Request Handling: The Front Controller pattern provides a centralized point for request handling, allowing for better control and coordination of the application flow. It ensures that all requests pass through a single-entry point, making it easier to implement cross-cutting concerns like authentication, logging, and error handling.
  • Code Reusability: By centralizing request handling and introducing Command Handlers, the Front Controller pattern promotes code reusability. Common tasks and actions can be encapsulated in Command Handlers, allowing them to be reused across multiple requests or even different parts of the application. This reduces code duplication and enhances maintainability.
  • Separation of Concerns: The Front Controller pattern promotes a clear separation of concerns by decoupling the request handling logic from the rest of the application. The Front Controller focuses on the coordination and routing of requests, while the Command Handlers encapsulate the specific business logic for each request. This separation enhances code readability, maintainability, and testability.
  • Improved Security: With a centralized Front Controller, security-related concerns can be handled consistently across the application. Authentication and authorization checks can be performed in a single location, ensuring that all requests pass through the necessary security measures. This promotes better security practices and reduces the risk of vulnerabilities.
  • Extensibility and Maintainability: The Front Controller pattern facilitates extensibility and maintainability by providing a structured approach to request handling. New actions or request types can be easily added by creating new Command Handlers and configuring the Front Controller to route the requests accordingly. This modularity and flexibility make it easier to maintain and evolve the application over time.
Disadvantages of Front Controller Design Pattern in Java:

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

  • Increased Complexity: Implementing the Front Controller pattern can introduce additional complexity to the application architecture. The introduction of a centralized Front Controller and Command Handlers may require additional configuration and infrastructure. Developers need to carefully design the request routing and ensure proper coordination between the Front Controller and Command Handlers.
  • Single Point of Failure: The Front Controller acts as a single-entry point for all requests, making it a potential single point of failure. If the Front Controller fails or becomes overwhelmed with requests, it can impact the entire application’s performance. Proper scalability measures and fault tolerance strategies need to be implemented to mitigate this risk.
  • Performance Overhead: The Front Controller pattern can introduce some performance overhead due to the centralized request handling and dispatching. The additional layers of abstraction and indirection may result in slightly slower request processing times compared to direct request handling approaches. However, the impact on performance is typically minimal and can be mitigated through proper optimization and caching strategies.
  • Limited Flexibility for Diverse Request Handling: The Front Controller pattern works well for applications with a consistent request handling flow. However, it may become less suitable for complex scenarios where different requests require highly customized handling or when the application needs to support diverse workflows. In such cases, implementing custom routing and request-handling mechanisms outside of the Front Controller may be necessary.

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

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