OpenAPITools 實踐

GoCoding發表於2021-11-05

OpenAPITools 可以依據 REST API 描述檔案,自動生成服務端樁(Stub)程式碼、客戶端 SDK 程式碼,及文件等。其是社群版的 Swagger ,差異可見:OpenAPI Generator vs Swagger Codegen

本文將從零開始設計和編寫 API 檔案,並生成 Go Gin 服務端程式碼,與 Python SDK 程式碼。更多語言或框架,也是一樣操作的。

快速開始

先熟悉下工具,直接用官方 Docker 映象生成 Petstore 樣例的 Go SDK 程式碼:

docker run --rm -v "${PWD}:/local" openapitools/openapi-generator-cli generate \
-i https://raw.githubusercontent.com/openapitools/openapi-generator/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml \
-g go \
-o /local/out/go

生成程式碼在當前目錄的 ./out/go

開啟 Swagger Editor File > Import URL 檢視 petstore.yaml API:

檢視 openapi-generator-cli 用法:

docker run --rm -it \
-v "${PWD}:/local" \
--entrypoint /bin/bash \
openapitools/openapi-generator-cli

ln -s /usr/local/bin/docker-entrypoint.sh /usr/local/bin/openapi-generator
openapi-generator help
openapi-generator help generate

動手實踐

設計 RESTful API

開啟 Swagger Editor 設計 API:

  • /albums

    • GET - Get all albums
    • POST - Create a new album
  • /albums/:id

    • GET - Get an album by its id
    • PUT - Update an album by its id
    • DELETE - Delete an album by its id

完整 API 描述檔案見 spec/api.yaml,主要包含三部分:

1 頭部: API 資訊

openapi: 3.0.0
info:
  title: Start OpenAPITools
  description: Let's practice designing our api.
  version: 0.1.0
  license:
    name: MIT
    url: https://spdx.org/licenses/MIT.html
servers:
  - url: https://github.com/ikuokuo/start-openapitools

2 中間: paths 及其操作 (get, post, etc.)

paths:
  /albums/{id}:
    get:
      tags:
        - album
      summary: Get an album by its id
      operationId: getAlbum
      parameters:
        - $ref: '#/components/parameters/AlbumId'
      responses:
        200:
          description: Get success, return the album
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Album'
        404:
          description: Album not found

3 底部: 可重用的 components,於文件裡 $ref 引用

components:
  parameters:
    AlbumId:
      name: id
      in: path
      description: Album id
      required: true
      schema:
        type: string
  schemas:
    Album:
      title: Album
      type: object
      required:
        - title
        - artist
        - price
      properties:
        id:
          type: string
          format: uuid
        title:
          type: string
          maxLength: 200
          minLength: 1
        artist:
          type: string
          maxLength: 100
          minLength: 1
        price:
          type: number
          format: double
          minimum: 0.0
        created_at:
          type: string
          format: date-time
        updated_at:
          type: string
          format: date-time

具體說明,請閱讀 OpenAPI Specification

線上生成程式碼

可以用線上服務快速生成程式碼:

以下則是自己動手生成的過程。

生成 Server Stub 程式碼

生成 Go Gin 樁(Stub)程式碼:

docker run --rm -it \
-v "${PWD}:/local" \
--entrypoint /bin/bash \
openapitools/openapi-generator-cli

ln -s /usr/local/bin/docker-entrypoint.sh /usr/local/bin/openapi-generator

# Config Options for go-gin-server
#  https://openapi-generator.tech/docs/generators/go-gin-server
openapi-generator config-help -g go-gin-server

openapi-generator generate \
-g go-gin-server \
-i /local/spec/swagger.yaml \
-o /local/out/gin-server \
--additional-properties=packageName=startapi

生成內容:

❯ tree out/gin-server -aF --dirsfirst
out/gin-server
├── .openapi-generator/
├── api/
│   └── openapi.yaml
├── go/
│   ├── README.md
│   ├── api_album.go
│   ├── api_albums.go
│   ├── model_album.go
│   └── routers.go
├── .openapi-generator-ignore
├── Dockerfile
└── main.go

簡單實現 GetAlbum 介面,位於 go/api_album.go

// GetAlbum - Get an album by its id
func GetAlbum(c *gin.Context) {
    c.JSON(http.StatusOK, Album{
        Id:        "3fa85f64-5717-4562-b3fc-2c963f66afa6",
        Title:     "Start OpenAPITools",
        Artist:    "GoCoding",
        Price:     0.99,
        CreatedAt: time.Now(),
        UpdatedAt: time.Now(),
    })
}

執行服務:

cd out/gin-server/
# 初始化模組
go mod init github.com/ikuokuo/start-openapitools/gin-server
go mod tidy

# 修改 `main.go` 中的 import 路徑
#  sw "github.com/ikuokuo/start-openapitools/gin-server/go"
# 替換成本地路徑
go mod edit -replace github.com/ikuokuo/start-openapitools/gin-server/go=./go

執行結果:

❯ go run .
2021/11/05 18:20:00 Server started
[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.

[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
 - using env:   export GIN_MODE=release
 - using code:  gin.SetMode(gin.ReleaseMode)

[GIN-debug] GET    /ikuokuo/start-openapitools/ --> github.com/ikuokuo/start-openapitools/gin-server/go.Index (3 handlers)
[GIN-debug] DELETE /ikuokuo/start-openapitools/albums/:id --> github.com/ikuokuo/start-openapitools/gin-server/go.DeleteAlbum (3 handlers)
[GIN-debug] GET    /ikuokuo/start-openapitools/albums/:id --> github.com/ikuokuo/start-openapitools/gin-server/go.GetAlbum (3 handlers)
[GIN-debug] PUT    /ikuokuo/start-openapitools/albums/:id --> github.com/ikuokuo/start-openapitools/gin-server/go.PutAlbum (3 handlers)
[GIN-debug] GET    /ikuokuo/start-openapitools/albums --> github.com/ikuokuo/start-openapitools/gin-server/go.GetAlbums (3 handlers)
[GIN-debug] POST   /ikuokuo/start-openapitools/albums --> github.com/ikuokuo/start-openapitools/gin-server/go.PostAlbums (3 handlers)
[GIN-debug] Listening and serving HTTP on :8080

❯ curl http://localhost:8080/ikuokuo/start-openapitools/
Hello World!

生成 Client SDK 程式碼

生成 Python SDK 程式碼:

docker run --rm -it \
-v "${PWD}:/local" \
--entrypoint /bin/bash \
openapitools/openapi-generator-cli

ln -s /usr/local/bin/docker-entrypoint.sh /usr/local/bin/openapi-generator

# Config Options for python
#  https://openapi-generator.tech/docs/generators/python
openapi-generator config-help -g python

openapi-generator generate \
-g python \
-i /local/spec/swagger.yaml \
-o /local/out/py-sdk \
--additional-properties=packageName=startapi \
--additional-properties=library=urllib3

生成內容:

❯ tree out/py-sdk -aF --dirsfirst
out/py-sdk
├── .openapi-generator/
├── docs/
├── startapi/
│   ├── api/
│   │   ├── __init__.py
│   │   ├── album_api.py
│   │   └── albums_api.py
│   ├── apis/
│   │   └── __init__.py
│   ├── model/
│   │   ├── __init__.py
│   │   └── album.py
│   ├── models/
│   │   └── __init__.py
│   ├── __init__.py
│   ├── api_client.py
│   ├── configuration.py
│   ├── exceptions.py
│   ├── model_utils.py
│   └── rest.py
├── test/
├── .gitignore
├── .gitlab-ci.yml
├── .openapi-generator-ignore
├── .travis.yml
├── README.md
├── git_push.sh
├── requirements.txt
├── setup.cfg
├── setup.py
├── test-requirements.txt
└── tox.ini

測試 SDK 使用,呼叫此前實現的 GetAlbum 介面:

❯ cd out/py-sdk/
❯ python - <<EOF
from startapi import ApiClient, Configuration, apis

config = Configuration(host="http://localhost:8080/ikuokuo/start-openapitools")
with ApiClient(configuration=config) as client:
  api = apis.AlbumApi(client)
  album = api.get_album("xxxxx")
  print(album)
EOF
{'artist': 'GoCoding',
 'created_at': datetime.datetime(2021, 11, 5, 18, 30, 0, 545305, tzinfo=tzoffset(None, 28800)),
 'id': '3fa85f64-5717-4562-b3fc-2c963f66afa6',
 'price': 0.99,
 'title': 'Start OpenAPITools',
 'updated_at': datetime.datetime(2021, 11, 5, 18, 30, 0, 545305, tzinfo=tzoffset(None, 28800))}

最後

實踐下來,感覺不錯。很多場合,生成 SDK 就夠用了。另外,生成自動化測試程式碼,也值得一試。

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