OpenAPI Specification

External

• OpenAPI 3.1.0 Specification https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md
• https://swagger.io/specification/

Internal

• OpenAPI
• API Concepts
• REST and Hypermedia
• Amazon API Gateway Integration
• JSON Schema

Overview

OpenAPI Specification (OAS), formerly Swagger Specification, is an API description format and a specification standard for HTTP REST APIs. The specification for an API can be expressed in a single file, which provides the source of truth for the API, starting with the API design phase, then continuing with client and server code generation, documentation and testing. The specification format is programming language agnostic, it is machine-readable and it can be used to generate code in different languages. API specifications are typically written in YAML or JSON. The latest version at the time of this writing is OpenAPI 3.1.0.

The OpenAPI specification describes endpoints and operations for each endpoint, input and output parameters for each operation, authentication methods, contact information, licenses, etc.

OpenAPI specification builds upon JSON Schema.

Endpoints

An endpoint is exposed in the OpenAPI specification by its relative path, declared in the paths map.

Refactor this.

Document Structure

openapi: 3.1.0
info: 
  [...]
servers:
   [...]
paths:
   [...]
components:
   [...]
webhooks:
   [...]
security:
   [...]
tags:
   [...]

openapi

The string following the openapi element is the version number of the OpenAPI specification this document uses.

info

https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#infoObject

info:
  title: OpenAPI Example
  version: 0.2.0
  summary: An OpenAPI example application 
  description:
  termsOfService:
  contact:
  license:

title

Required element. Represents the title of the API. When imported in AWS API Gateway, the title provides the API name, unless the AWS::ApiGateway::RestApi resource explicitly specifies a title, in which case the title specified by AWS::ApiGateway::RestApi will take priority.

version

Required element. Represents the version of the API document. It is different from openapi version string.

summary

A short summary of the API.

description

A description of the API. CommonMark syntax may be used for rich text representation.

servers

https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#serverObject

servers:
  - url: https://petstore.swagger.io/v2

paths

https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#pathsObject

paths:
 /a:
    summary:
    description: 
    get: [...]
    put: [...]
    post: [...]
    delete: [...]
    options: [...]
    head: [...]
    patch: [...]
    trace: [...]
    servers:
    parameters:
 /b:
   [...]
 /c:
   [...]

Contains a map of relative paths to individual endpoints.

For syntax of individual path specifications, see:

OpenAPI Specification Path

components

https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#componentsObject

components:
  schemas:
    Pet:
      [...]
    Error:
      [...]

schemas

The /components/schemas section of the OpenAPI specification defines reusable objects.

OpenAPI Specification Schemas

webhooks

A map of path item objects or reference objects.

security

https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#securityRequirementObject

tags

https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#tagObject

Data Types

https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#data-types

OAS data types are based on those supported by JSON Schema Specification Draft 2020-12

Type	Format	Comments
null		A JSON "null" value. JSON Schema Specification type.
boolean		A "true" or "false" value. JSON Schema Specification type.
object		An unordered set of properties mapping a string to an instance. JSON Schema Specification type.
array		An ordered list of instances. JSON Schema Specification type.
number		An arbitrary-precision, base-10 decimal number value. JSON Schema Specification type.
string		A string of Unicode code points. JSON Schema Specification type.
integer	int32	Signed 32 bits. Introduced by OAS.
integer	int64	Signed 64 bits (long). Introduced by OAS.
number	float	Introduced by OAS.
number	double	Introduced by OAS.
string	password	A hint to UIs to obscure input. Introduced by OAS.
string	date	See github.com/oapi-codegen/runtime/types/date.go
string	email	See github.com/oapi-codegen/runtime/types/email.go
string	file	See github.com/oapi-codegen/runtime/types/file.go
string	uuid	See github.com/oapi-codegen/runtime/types/uuid.go

OpenAPI Operation Declaration and Implementation Examples

OpenAPI Examples

A Simple CRUD REST Application with OpenAPI

A Simple CRUD REST Application with OpenAPI