dto

A Data Transfer Object (DTO) is a simple object that carries data between processes, layers, or subsystems. DTOs are designed to hold data with no or minimal behavior, and they are often serializable for transport over a network or across boundaries such as between a client and a server.

DTOs are commonly used to decouple internal domain models from external representations. They aggregate data from one or more domain objects and present it in a form suitable for transfer, reducing the number of remote calls and controlling what data is exposed to clients. DTOs are frequently employed in service interfaces, APIs, and inter-service communication, as well as when interfacing with user interfaces or external systems.

DTOs differ from domain models and entities in that they focus on data transport rather than encapsulating business logic or invariants. Mapping between domain objects and DTOs is a common concern and may be manual or performed with automated mappers. DTOs are typically designed to be lightweight, serializable, and versionable, with an emphasis on immutability and a minimal, well-defined schema.

Design considerations include choosing which data to include, ensuring compatibility across versions, and selecting appropriate serialization formats (JSON, XML, etc.). Developers often employ flat DTOs or nested structures, depending on needs, and use mapping tools to reduce boilerplate code. Common tools include AutoMapper, MapStruct, or language-specific facilities for object serialization.

Use cases span API responses and requests, inter-service communication, and client-server data exchange, where DTOs help enforce boundaries, improve performance by reducing overfetch, and simplify data shaping. Critics note that excessive DTO usage can add boilerplate and maintenance effort if not paired with clear mapping strategies and stable boundaries.