DTOs in REST APIs: To Use or Not?

Dilemma of DTOs in REST APIs: To Use or Not?

Developers designing REST APIs often grapple with the question of whether to expose domain models directly or employ Data Transfer Objects (DTOs). This debate stems from conflicting opinions on maintaining consistency, code bloat, and flexibility.

Decoupling Concerns and Flexibility

Advocates of DTOs emphasize the importance of decoupling API models from domain models. This approach enhances flexibility by preventing changes in domain models from affecting API clients. It also allows for controlled exposure of data, omitting unnecessary and sensitive information for external consumption.

Avoiding Redundancy and Complexity

By using DTOs, developers can tailor models specifically for API needs, avoiding redundant attributes and annotations in domain models. This streamlines code and prevents the proliferation of non-persistence related annotations.

Benefits of DTOs in REST APIs

The key benefits of using DTOs include:

• Decouples API models from domain models
• Customizes exposure of attributes
• Reduces annotations in domain entities
• Controls data received for resource creation and updates
• Supports documentation using annotations
• Allows for multiple API versions and DTOs
• Enhances flexibility in relationship mapping
• Facilitate HATEOAS

Streamlining Mapping

Addressing concerns about boilerplate mapping code, frameworks like MapStruct and Lombok offer automated mapping solutions. These tools generate getters, setters, equals/hashcode methods, and facilitate the conversion between domain models and DTOs.

Conclusion

Given the compelling benefits and flexibility offered by DTOs, they emerge as a recommended approach for REST API modeling. Decoupling API concerns from domain models simplifies evolution, documentation, and maintenance of REST APIs. While the use of mapping frameworks mitigates the issue of code bloat, the decoupling architecture provided by DTOs offers a robust and scalable solution for REST APIs.

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