Clean Architecture & Design Patterns in Practice · Lesson

Adapting to Web Frameworks

Learn strategies for integrating Clean Architecture with popular web frameworks (e.g., Spring, ASP.NET, Django) without coupling to them.

Adapting to Web Frameworks is a free Clean Architecture & Design Patterns in Practice lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Clean Architecture & Design Patterns in Practice learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Frameworks & Clean Architecture

Web frameworks like Spring, Django, or ASP.NET are powerful tools for building applications. But how do they fit into a Clean Architecture?

The challenge is to leverage their features without letting them dictate or couple to our core business logic. This lesson explores strategies to achieve that separation.

Avoiding Framework Coupling

Coupling occurs when one part of your code is highly dependent on another. In Clean Architecture, we want our inner layers (Entities, Use Cases) to be independent.

If your Use Cases directly import Spring annotations or Django models, they are coupled.
This makes it hard to change frameworks, test core logic, or reuse components.

The Dependency Rule Applied

Remember the Dependency Rule? Dependencies can only flow inwards. This is crucial for framework integration.

Your core business logic (Entities, Use Cases) should never know about the web framework.
The web framework (an outer layer) can and should depend on your core logic.

We need a bridge that respects this rule.

Presenters & Adapters Bridge

The 'Frameworks & Drivers' layer is where our web framework lives. To communicate with the inner 'Interface Adapters' layer (which contains Presenters and Controllers), we use specific patterns:

Adapters: Translate incoming framework-specific requests into a format our Use Cases understand.
Presenters: Format the output from Use Cases into a structure suitable for the web framework's views or JSON responses.

The Web Controller as an Adapter

In web applications, the framework's controller often serves as the primary adapter. Its job is to:

Receive HTTP requests (e.g., from a browser or API client).
Extract relevant data from the request.
Convert this data into a simple object (a Request Model) that matches the Use Case's Input Port.
Call the Use Case.
Receive output from the Use Case (a Response Model).
Pass this output to a Presenter to format the final HTTP response.

Defining an Input Port

Our Use Cases expose simple interfaces, called Input Ports. The web controller will depend on this interface, not the concrete Use Case implementation. This keeps the Use Case truly independent.

Here's an example of an Input Port and its corresponding Request object:

interface AddItemInputPort {
    void execute(AddItemRequest request);
}

class AddItemRequest {
    public final String itemName;
    public final double price;

    public AddItemRequest(String itemName, double price) {
        this.itemName = itemName;
        this.price = price;
    }
}

public class Main {
    public static void main(String[] args) {
        // These are just definitions, not runnable logic on their own.
        // We'll see them in action soon!
        System.out.println("InputPort and Request defined.");
    }
}

Implementing a Use Case

The actual business logic resides within the Use Case. It implements the AddItemInputPort and performs the operation, completely unaware of how it was invoked (e.g., by a web request, a CLI, or a message queue).

interface AddItemInputPort {
    void execute(AddItemRequest request);
}

class AddItemRequest {
    public final String itemName;
    public final double price;

    public AddItemRequest(String itemName, double price) {
        this.itemName = itemName;
        this.price = price;
    }
}

class AddItemUseCase implements AddItemInputPort {
    @Override
    public void execute(AddItemRequest request) {
        System.out.println("Use Case: Processing item '" +
                           request.itemName + "' with price $" +
                           request.price + ".");
        // In a real application, this would involve business rules,
        // interacting with entities, and potentially repositories.
    }
}

public class Main {
    public static void main(String[] args) {
        AddItemInputPort useCase = new AddItemUseCase();
        AddItemRequest request = new AddItemRequest("Fancy Pen", 15.75);
        useCase.execute(request);
    }
}

Web Controller Adapter in Action

Now, let's see how a simplified web controller (acting as an adapter) uses our Use Case. Notice it only interacts with the AddItemInputPort interface, not the concrete AddItemUseCase class.

interface AddItemInputPort {
    void execute(AddItemRequest request);
}

class AddItemRequest {
    public final String itemName;
    public final double price;
    public AddItemRequest(String itemName, double price) {
        this.itemName = itemName;
        this.price = price;
    }
}

class AddItemUseCase implements AddItemInputPort {
    @Override
    public void execute(AddItemRequest request) {
        System.out.println("Use Case processed: " + request.itemName);
    }
}

// This class simulates a web framework controller
class WebFrameworkController {
    private final AddItemInputPort addItemInputPort;

    // Controller depends on the Input Port interface
    public WebFrameworkController(AddItemInputPort addItemInputPort) {
        this.addItemInputPort = addItemInputPort;
    }

    // This method simulates handling an HTTP POST request
    public String handleHttpRequest(String name, double cost) {
        System.out.println("Controller received HTTP request for: " + name);
        AddItemRequest request = new AddItemRequest(name, cost);
        addItemInputPort.execute(request); // Delegate to Use Case
        return "HTTP Response: Item '" + name + "' added.";
    }
}

public class Main {
    public static void main(String[] args) {
        // Setup: Inject the Use Case into the Controller
        AddItemInputPort useCase = new AddItemUseCase();
        WebFrameworkController controller = new WebFrameworkController(useCase);

        // Simulate an incoming web request
        String response = controller.handleHttpRequest("Notebook", 8.99);
        System.out.println(response);
    }
}

Benefits of Decoupling Frameworks

This adapter-based approach offers significant advantages:

Testability: Use Cases can be tested in isolation, without needing to boot up the entire web framework.
Maintainability: Changes or upgrades to your web framework have minimal impact on your core business logic.
Flexibility: You could swap out your web framework for another (e.g., from Spring to JAX-RS) with changes only in the outer 'Frameworks & Drivers' layer.
Framework Independence: Your valuable business rules are not tied to a specific technology vendor.

Check Your Understanding

Which of the following best describes the role of a web controller when integrating a Clean Architecture application with a web framework?

Recap: Framework Integration

In this lesson, we explored how to integrate web frameworks into a Clean Architecture application while maintaining crucial separation:

We treat the web framework as an outer layer that depends on our core logic, not the other way around.
Controllers in the web framework act as adapters, translating web requests into Use Case Input Ports and formatting Use Case output.
This approach ensures high testability, maintainability, and framework independence for your core application.

Frequently asked questions

Is the “Adapting to Web Frameworks” lesson free?

Yes — the full text of “Adapting to Web Frameworks” is free to read here on the web, and the Clean Architecture & Design Patterns in Practice course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Clean Architecture & Design Patterns in Practice course, upgrade to CoddyKit PRO.

What will I learn in “Adapting to Web Frameworks”?

Learn strategies for integrating Clean Architecture with popular web frameworks (e.g., Spring, ASP.NET, Django) without coupling to them. You practise Clean Architecture & Design Patterns in Practice with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Clean Architecture & Design Patterns in Practice?

No prior experience is required. Clean Architecture & Design Patterns in Practice on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Adapting to Web Frameworks” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Clean Architecture & Design Patterns in Practice lesson?

Yes. Every Clean Architecture & Design Patterns in Practice lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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