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API Rest

API (Application Programming Interface)

Is a set of protocols and definitions used in development or integration of an application.

Basically the api is a contract of how the data will be sent and which responses we will receive when specific data is requested.

Ex: Client -> Waiter(API) -> Kitchen (Server)

sequenceDiagram
    participant Client
    participant API as Waiter
    participant Server as Kitchen
    Client->>API: Request (e.g., GET /items)
    API->>Server: Forward request / orchestrate
    Server-->>API: Response (data/status)
    API-->>Client: Response (JSON)

REST (Representational State Transfer)

Is a set of guidelines so the api is not too complex and follow a standard.

Basically we ask to an API which is it's state and it returns a representation of it in a data transfer.

The asking is made requesting an URI (Uniform Resource Identifier) is known as an endpoint, route or resource like http://localhost:5000/resource/1

The transfer is made usings HTTP ( Hyper Text Transfer Protocol)

Constraints

  • Client-Server: Separation between client and server.
  • Stateless: Each request must be independent and treat as if was the first request ever seen from the client. The server does not remember that the client was authenticated on previous session, is necessary to send also the session to the next request, tokens can be used for that.
  • Cacheable: Response messages from the server to the client are explicitly labeled as cacheable or not cacheable.
  • Uniform Interface: Must have a uniform interface between all clients and servers (web, mobile, ...)
  • Layered System: A client have access to an endpoint that rely on other endpoints without have to know all underling implementations.
  • Code on demand (optiona): Code to be sent to the sever to the client to allow it's execution, like javascript.

Verbs

  • GET
  • POST
  • PUT
  • DELETE
  • HEAD
  • OPTIONS

Status Codes

  • 2**: Is Ok
  • 4**: You made a mistake
  • 5**: Server is broken

Request

1
curl -X http://localhost:5000/resource/1

RESTful

RESTful means following or implementing a set of standards known as REST.