OpenAPITools 可以依据 REST API 描述文件，自动生成服务端桩（Stub）代码、客户端 SDK 代码，及文档等。其是社区版的 Swagger ，差异可见：OpenAPI Generator vs Swagger Codegen。
本文将从零开始设计和编写 API 文件，并生成 Go Gin 服务端代码，与 Python SDK 代码。更多语言或框架，也是一样操作的。
快速开始
先熟悉下工具，直接用官方 Docker 镜像生成 Petstore 样例的 Go SDK 代码：
docker run --rm -v "${PWD}:/local" openapitools/openapi-generator-cli generate \
-i https://raw.githubusercontent.com/openapitools/openapi-generator/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml \
-g go \
-o /local/out/go
生成代码在当前目录的 ./out/go 。
打开 Swagger Editor File > Import URL 查看 petstore.yaml API：
查看 openapi-generator-cli 用法:
docker run --rm -it \
-v "${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
动手实践
设计 RESTful API
打开 Swagger Editor 设计 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 描述文件见 spec/api.yaml，主要包含三部分：
1 头部： API 信息
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 中间： 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，于文档里 $ref 引用
components:
parameters:
AlbumId:
name: id
in: path
description: Album id
required: true
schema:
type: string
schemas:
Album:
title: Album
type: object
required:
- title
- artist
- price
properties:
id:
type: string
format: uuid
title:
type: string
maxLength: 200
minLength: 1
artist:
type: string
maxLength: 100
minLength: 1
price:
type: number
format: double
minimum: 0.0
created_at:
type: string
format: date-time
updated_at:
type: string
format: date-time
具体说明，请阅读 OpenAPI Specification。
在线生成代码
可以用线上服务快速生成代码：
- latest stable version: https://api.openapi-generator.tech
以下则是自己动手生成的过程。
生成 Server Stub 代码
生成 Go Gin 桩（Stub）代码：
docker run --rm -it \
-v "${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
生成内容：
❯ 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
简单实现 GetAlbum 接口，位于 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(),
})
}
运行服务：
cd out/gin-server/
# 初始化模块
go mod init github.com/ikuokuo/start-openapitools/gin-server
go mod tidy
# 修改 `main.go` 中的 import 路径
# sw "github.com/ikuokuo/start-openapitools/gin-server/go"
# 替换成本地路径
go mod edit -replace github.com/ikuokuo/start-openapitools/gin-server/go=./go
运行结果：
❯ 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 代码
生成 Python SDK 代码：
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
生成内容：
❯ 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
测试 SDK 使用，调用此前实现的 GetAlbum 接口：
❯ 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))}
最后
实践下来，感觉不错。很多场合，生成 SDK 就够用了。另外，生成自动化测试代码，也值得一试。
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