DTOs: To Use or Not To Use in REST API Design?

REST API: DTOs or Not?

Data transfer objects (DTOs) have been a subject of debate in REST API design. Some advocate against DTOs and suggest exposing the domain model directly, while others emphasize the benefits of using them.

Benefits of Using DTOs

DTOs provide several advantages:

• Separation of concerns: Decoupling domain models from API models ensures API stability, allowing changes in one domain without affecting the other.
• Customization: DTOs can be tailored to specific needs, exposing only necessary attributes and omitting irrelevant data.
• Reduced annotations: By using DTOs, annotations for persistence can be kept separate from API-related annotations, minimizing annotation bloat.
• Control over exposed attributes: DTOs allow complete control over data received or updated, preventing unauthorized or excessive data exposure.
• Documentation: DTOs can be documented using Swagger's annotations, providing a clear understanding of API structure.
• Versioning: Multiple DTO versions can accommodate API evolution, allowing for deprecation and the creation of new versions as needed.
• Flexible relationship mapping: DTOs provide more flexibility in mapping relationships, allowing for selective inclusion or exclusion of related data.
• Media type support: DTOs can be used for different media types, ensuring compatibility with various clients.
• HATEOAS: DTOs can include links for HATEOAS, providing clients with easy navigation and discovery of related resources.

Addressing Mapping Boilerplate

MappingDTOs can be automated using frameworks like MapStruct, which generates mapping code from annotations. Additionally, Lombok can help generate getters, setters, and other boilerplate methods.

Conclusion

DTOs offer significant benefits for REST APIs, including separation of concerns, customization, reduced annotations, and increased flexibility. While manual mapping can be tedious, automation tools can alleviate this concern. By using DTOs, developers gain more control over API data exposure, improve API stability, and enhance the overall design of RESTful services.

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