How to Design Efficient and Consistent Request DTOs in ServiceStack?

ServiceStack Request DTO Design

In RESTful APIs, it's common to have multiple services serving different purposes. While it's tempting to create a separate service for every unique request, it can lead to unnecessary duplication and a bloated architecture. ServiceStack promotes a different approach, encouraging the grouping of services based on their call semantics and response types.

Distinguishing Service Operations vs Types

Service operations (Request DTOs) should capture the unique actions of a service, while the DTO types they return represent entities or data containers. Request DTOs should use verbs (e.g., "Get", "Find") to convey their actions, while DTO types should use nouns (e.g., "Customer", "Product") to represent their entities.

Returning Generic Responses

In the case of a typical GET request, ServiceStack does not require a ResponseStatus property in response DTOs. Instead, the generic ErrorResponse DTO will be thrown and serialized on the client if an error occurs. This eliminates the need for explicit ResponseStatus properties in your responses.

Consistent Nomenclature

To enhance readability and self-description, it's recommended to use consistent nomenclature in your service contracts. Reserve the "Get" verb for services that retrieve a single result based on a unique identifier. For search services that return multiple results, use "Find" or "Search" prefixes. Additionally, provide clear and descriptive property names that indicate their purpose within the request DTOs.

Re-factored Booking Limits Services

Based on these principles, the following refactored Booking Limits services are proposed:

[Route("/bookinglimits/{Id}")]
public class GetBookingLimit : IReturn<BookingLimit>
{
    public int Id { get; set; }
}

public class BookingLimit
{
    public int Id { get; set; }
    public int ShiftId { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }
    public int Limit { get; set; }
}

[Route("/bookinglimits/search")]
public class FindBookingLimits : IReturn<List<BookingLimit>>
{
    public DateTime BookedAfter { get; set; }
}

Service Implementation

The service implementation can be simplified by applying the [Authenticate] attribute once on the service class instead of each request DTO. The following code shows this implementation:

[Authenticate]
public class BookingLimitService : AppServiceBase
{ 
    public BookingLimit Get(GetBookingLimit request) { ... }

    public List<BookingLimit> Get(FindBookingLimits request) { ... }
}

Error Handling and Validation

Error handling and validation can be customized using ServiceStack's built-in Fluent Validation capabilities. Instead of injecting validators into the service, you can register them in the AppHost with the following line:

container.RegisterValidators(typeof(CreateBookingValidator).Assembly);

For operations with side effects (e.g., POST/PUT), you can define validators such as the following:

public class CreateBookingValidator : AbstractValidator<CreateBooking>
{
    public CreateBookingValidator()
    {
        RuleFor(r => r.StartDate).NotEmpty();
        RuleFor(r => r.ShiftId).GreaterThan(0);
        RuleFor(r => r.Limit).GreaterThan(0);
    }
}

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