Data Transfer Object (DTO)¶

In Litestar, a Data Transfer Object (DTO) is a class that is used to control the flow of data from the client into a useful form for the developer to use in their handler, and then back again.

The following diagram demonstrates how the DTO is used within the context of an individual request in Litestar:

        sequenceDiagram
    autonumber
    actor Client
    participant Litestar
    participant DTO
    participant Handler
    Client->>Litestar: Data as encoded bytes
    activate Litestar
    Litestar->>DTO: Encoded data
    deactivate Litestar
    activate DTO
    Note over DTO: Perform primitive type validation<br>and conversion into data model
    DTO->>Handler: Data injected into handler
    deactivate DTO
    activate Handler
    Note over Handler: Handler receives data as type<br>declared in handler signature<br>and performs business logic
    Handler->>DTO: Data returned from handler
    deactivate Handler
    activate DTO
    Note over DTO: Data returned from the handler<br>is converted into a type that <br>Litestar can encode into bytes
    DTO->>Litestar: Litestar encodable type
    deactivate DTO
    activate Litestar
    Note over Litestar: Data received from DTO<br>is encoded into bytes
    Litestar->>Client: Data as encoded bytes
    deactivate Litestar

Data movement¶

The following is a short summary of the interaction between each of the participants in the above diagram.

Data moves between each of the participants in the DTO chart, and as it does so, different actions are performed on the data, and it takes different forms depending on the direction of data transfer, and the participants on either end of the transfer. Lets take a look at each of these data movements:

Client → Litestar → DTO¶

Data is received from the client as encoded bytes
In most cases, the unencoded bytes are passed directly to the DTO
Exception is multipart and URL encoded data, which is decoded into python built-in types before being passed to the DTO

DTO → Handler¶

DTO receives data from client
Performs primitive type validation
Marshals the data into the data type declared in the handler annotation

Handler → DTO¶

Handler receives data as type declared in handler signature
Developer performs business logic and returns data from handler

DTO → Litestar¶

DTO receives data from handler
Marshals the data into a type that can be encoded into bytes by Litestar

Litestar → Client¶

Data is received from the DTO as a type that Litestar can encode into bytes
Data is encoded into bytes and sent to the client