OpenAPI/Swagger: API-Dokumentation

OpenAPI ist der Standard für REST-API-Dokumentation. Lernen Sie, wie Sie Ihre API professionell dokumentieren.

Grundstruktur

# openapi.yaml
openapi: 3.0.3
info:
  title: My API
  description: API für meine Anwendung
  version: 1.0.0
  contact:
    email: api@example.com

servers:
  - url: https://api.example.com/v1
    description: Production
  - url: https://staging-api.example.com/v1
    description: Staging

paths:
  /users:
    get:
      # ...
    post:
      # ...

components:
  schemas:
    User:
      # ...
  securitySchemes:
    bearerAuth:
      # ...

Paths und Operations

paths:
  /users:
    get:
      summary: Liste aller Benutzer
      description: Gibt eine paginierte Liste aller Benutzer zurück
      operationId: getUsers
      tags:
        - Users
      parameters:
        - name: page
          in: query
          description: Seitennummer
          schema:
            type: integer
            default: 1
        - name: limit
          in: query
          description: Einträge pro Seite
          schema:
            type: integer
            default: 20
            maximum: 100
      responses:
        '200':
          description: Erfolgreiche Antwort
          content:
            application/json:
              schema:
                type: object
                properties:
                  data:
                    type: array
                    items:
                      $ref: '#/components/schemas/User'
                  pagination:
                    $ref: '#/components/schemas/Pagination'
        '401':
          $ref: '#/components/responses/Unauthorized'

    post:
      summary: Benutzer erstellen
      operationId: createUser
      tags:
        - Users
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateUserRequest'
      responses:
        '201':
          description: Benutzer erstellt
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/User'
        '400':
          $ref: '#/components/responses/ValidationError'

  /users/{id}:
    get:
      summary: Benutzer abrufen
      operationId: getUser
      tags:
        - Users
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: integer
      responses:
        '200':
          description: Erfolg
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/User'
        '404':
          $ref: '#/components/responses/NotFound'

Schemas (Datenmodelle)

components:
  schemas:
    User:
      type: object
      required:
        - id
        - email
        - name
      properties:
        id:
          type: integer
          example: 123
        email:
          type: string
          format: email
          example: user@example.com
        name:
          type: string
          minLength: 2
          maxLength: 100
          example: Max Mustermann
        role:
          type: string
          enum: [user, admin, moderator]
          default: user
        createdAt:
          type: string
          format: date-time
        profile:
          $ref: '#/components/schemas/UserProfile'

    CreateUserRequest:
      type: object
      required:
        - email
        - name
        - password
      properties:
        email:
          type: string
          format: email
        name:
          type: string
          minLength: 2
        password:
          type: string
          minLength: 8
          format: password

    Pagination:
      type: object
      properties:
        page:
          type: integer
        limit:
          type: integer
        total:
          type: integer
        totalPages:
          type: integer

Authentifizierung

components:
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT

    apiKey:
      type: apiKey
      in: header
      name: X-API-Key

    oauth2:
      type: oauth2
      flows:
        authorizationCode:
          authorizationUrl: https://auth.example.com/authorize
          tokenUrl: https://auth.example.com/token
          scopes:
            read: Lesezugriff
            write: Schreibzugriff

# Global anwenden
security:
  - bearerAuth: []

# Oder pro Operation
paths:
  /public:
    get:
      security: []  # Keine Auth
  /private:
    get:
      security:
        - bearerAuth: []

Fehler-Responses

components:
  responses:
    NotFound:
      description: Ressource nicht gefunden
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            error:
              code: NOT_FOUND
              message: Die angeforderte Ressource wurde nicht gefunden

    ValidationError:
      description: Validierungsfehler
      content:
        application/json:
          schema:
            type: object
            properties:
              error:
                type: object
                properties:
                  code:
                    type: string
                    example: VALIDATION_ERROR
                  message:
                    type: string
                  details:
                    type: array
                    items:
                      type: object
                      properties:
                        field:
                          type: string
                        message:
                          type: string

    Unauthorized:
      description: Nicht authentifiziert
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'

  schemas:
    Error:
      type: object
      properties:
        error:
          type: object
          properties:
            code:
              type: string
            message:
              type: string

Tools

# Swagger UI (Interaktive Dokumentation)
docker run -p 8080:8080 \
  -e SWAGGER_JSON=/spec/openapi.yaml \
  -v ./openapi.yaml:/spec/openapi.yaml \
  swaggerapi/swagger-ui

# Swagger Editor (online)
# editor.swagger.io

# Code-Generierung
npx @openapitools/openapi-generator-cli generate \
  -i openapi.yaml \
  -g typescript-fetch \
  -o ./generated-client

# Validierung
npx @redocly/cli lint openapi.yaml

# Redoc (Alternative zu Swagger UI)
npx @redocly/cli build-docs openapi.yaml

Aus Code generieren

// Node.js: swagger-jsdoc
/**
 * @openapi
 * /users:
 *   get:
 *     summary: Liste aller Benutzer
 *     responses:
 *       200:
 *         description: Erfolg
 */
app.get('/users', getUsers);

// PHP: zircote/swagger-php
/**
 * @OA\Get(
 *     path="/users",
 *     summary="Liste aller Benutzer",
 *     @OA\Response(response="200", description="Erfolg")
 * )
 */
public function getUsers() {}

Weitere Informationen

• 📐 API Design Best Practices
• 🚀 REST API erstellen
• 📊 Enjyn Status Monitor