Should You Use DTOs in Your REST API?

REST API - DTOs: Yes or No?

When developing a REST API, the question of whether to use DTOs (Data Transfer Objects) or expose the domain model directly has sparked ongoing debate. Some argue against DTOs, advocating for direct exposure of domain models, while others maintain the benefits of using DTOs.

Benefits of Using DTOs

Despite the controversy, DTOs offer significant advantages:

• Decoupling: DTOs separate domain models from API models, insulating API clients from changes in the domain layer.
• Flexibility: DTOs allow for targeted exposure of data attributes, reducing the need for annotations to exclude fields from serialization.
• Avoidance of Annotations: DTOs prevent unnecessary annotations in persistence entities, maintaining a clean separation of concerns.
• Customizable Control: DTOs grant full control over received attributes during resource creation or updates.
• Documentation Enhancement: DTOs enable the use of annotations like "@ApiModel" and "@ApiModelProperty" in Swagger for API documentation.
• Versioning: Distinct DTO versions support the gradual evolution of API models.
• Relationship Mapping Flexibility: DTOs provide flexibility in mapping relationships between objects.
• Media Type Compatibility: Different DTOs can be designed for various media types.
• HATEOAS Integration: DTOs can host links for HATEOAS, simplifying the discovery of related resources.

Addressing Boilerplate Code

While DTOs may introduce duplicate mapping code, there are effective solutions to mitigate this overhead. Mapping frameworks like MapStruct and Lombok can automate the mapping process and generate necessary boilerplate code.

Conclusion

DTOs offer compelling benefits for REST APIs by decoupling domain models, enhancing flexibility, and providing customizable control over data exposure. While boilerplate code can be an initial concern, using mapping frameworks and code generation techniques can effectively address this issue. Therefore, leveraging DTOs when developing REST APIs is recommended for the advantages they bring.

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