What is the role of SAP Gateway in OData service implementation?

SAP Gateway is the technical component/framework responsible for translating between the OData protocol (HTTP requests/responses) and SAP's backend business logic — handling the protocol-level details (parsing query options like $filter, formatting responses as JSON/XML) so developers implementing a service focus on the actual business logic rather than HTTP/OData mechanics themselves.

flowchart LR
    A[Fiori app: HTTP OData request] --> B[SAP Gateway: parses OData request]
    B --> C[Service implementation: business logic executes]
    C --> D[SAP Gateway: formats response as OData/JSON]
    D --> A

In classical development, this meant implementing specific methods (like GET_ENTITYSET) in a Gateway service class that Gateway calls at the right moment during request processing. In RAP-based development, this translation happens more automatically based on the CDS View and behavior definition, with Gateway's role largely handled transparently by the framework rather than requiring explicit implementation classes for basic scenarios.