What is an Anti-Corruption Layer and how was it organized?

Anti-Corruption Layer (ACL) is a pattern from Domain-Driven Design that serves to isolate and protect the internal model of the domain from the influence of external systems or contexts with different models.

The main idea of ACL is to create an adaptation layer that translates data and commands from external systems into a comprehensible internal format and vice versa, preventing "corruption" of the internal model due to incompatible concepts or data structures.

Organizing ACL typically includes:

• Facades or adapters that accept calls from external systems and transform them into calls for the internal domain.
• Mappers that convert objects and data between external and internal models.
• Isolating interfaces so that internal code does not depend directly on external APIs.

Example in Java:

// External DTO
class ExternalUserDTO {
    String fullName;
    String emailAddress;
}

// Internal model
class User {
    private String firstName;
    private String lastName;
    private String email;
    // getters and setters
}

// ACL Adapter
class UserAntiCorruptionLayer {
    public User convert(ExternalUserDTO dto) {
        String[] parts = dto.fullName.split(" ");
        User user = new User();
        user.setFirstName(parts[0]);
        user.setLastName(parts.length > 1 ? parts[1] : "");
        user.setEmail(dto.emailAddress);
        return user;
    }
}

Thus, ACL ensures the purity and integrity of the internal model, allowing integration with external systems without directly affecting the domain logic.