Anti-Corruption Layer in DDD

Introduction

The Anti-Corruption Layer (ACL) is a design pattern in Domain-Driven Design (DDD) that acts as a barrier between different systems, ensuring that the integrity of the domain model is maintained. It translates requests and responses between the domain model and external systems.

What is an Anti-Corruption Layer?

The ACL serves to protect the domain model from external influences and prevents unwanted dependencies. It ensures that any interaction with external systems is mediated in a way that the internal model remains unaffected by changes in those external systems.

Importance of ACL

Using an ACL is critical for several reasons:

• Isolates the domain model from external changes.
• Facilitates easier integration with third-party systems.
• Improves maintainability and adaptability of the domain model.
• Encourages adherence to the principles of DDD.

Implementing an ACL

Implementing an ACL involves several steps:

1. Identify external systems that interact with your domain.
2. Define interfaces that the ACL will implement.
3. Translate requests and responses between the external systems and your domain model.
4. Test the ACL to ensure it properly mediates interactions.

Code Example: Basic ACL Implementation

class ExternalService {
    public function fetchData() {
        // Simulated external data fetching
        return ['name' => 'John Doe', 'age' => 30];
    }
}

class User {
    private $name;
    private $age;

    public function __construct($name, $age) {
        $this->name = $name;
        $this->age = $age;
    }
}

class UserACL {
    private $externalService;

    public function __construct(ExternalService $service) {
        $this->externalService = $service;
    }

    public function getUser() {
        $data = $this->externalService->fetchData();
        return new User($data['name'], $data['age']);
    }
}

$service = new ExternalService();
$acl = new UserACL($service);
$user = $acl->getUser();
echo $user;
        

Best Practices

Here are some best practices for implementing an ACL:

• Keep the ACL simple and focused on translation.
• Use adapters to abstract different external systems.
• Document the mapping between the external model and your domain model.
• Regularly review and refactor the ACL as external systems evolve.

FAQ