apig: Golang RESTful API Server Generator

apig is an RESTful API server generator.

• Input: Model definitions based on gorm annotated struct
• Output: RESTful JSON API server using gin including tests and documents

Contents

• Contents
• How to build and install
• How to use
  • 1. Generate boilerplate
  • 2. Write model code
  • 3. Generate controllers, tests, documents etc. based on models.
  • 4. Build and run server
• Usage
  • new command
  • gen command
  • API Document
• API server specification
  • Endpoints
  • Available URL parameters
  • Data Type
  • Pagination
  • Versioning
• License

How to build and install

Go 1.16 or higher is required.

After installing required version of Go, you can build and install apig by

$ go get -d -u github.com/shimastripe/apig
$ cd $GOPATH/src/github.com/shimastripe/apig
$ make
$ make install

make generates binary into bin/apig. make install put it to $GOPATH/bin.

How to use

1. Generate boilerplate

First, creating by apig new command.

$ apig new -u shimastripe apig-sample

generates Golang API server boilerplate under $GOPATH/src/github.com/shimastripe/apig-sample. apig supports two database engines; SQLite (sqlite) and PostgreSQL (postgres) and Mysql (mysql). You can specify this by -d, -database option.

Available command line options of apig new command are:

Option	Description	Required	Default
-d, -database	Database engine		sqlite
-n, -namespace	Namespace of API		(empty)
-u, -user	Username		github username
--vcs	VCS		github.com

2. Write model code

Second, write model definitions under models/. For example, user and email model is like below:

// models/user.go
package models

import "time"

type User struct {
	ID        uint       `gorm:"primary_key;AUTO_INCREMENT" json:"id" form:"id"`
	Name      string     `json:"name" form:"name"`
	Emails    []Email    `json:"emails" form:"emails"`
	CreatedAt *time.Time `json:"created_at" form:"created_at"`
	UpdatedAt *time.Time `json:"updated_at" form:"updated_at"`
}

// models/email.go
package models

type Email struct {
	ID      uint   `gorm:"primary_key;AUTO_INCREMENT" json:"id" form:"id"`
	UserID  uint   `json:"user_id" form:"user_id"`
	Address string `json:"address" form:"address"`
	User    *User  `json:"user form:"user`
}

This models are based on gorm structure. Please refer gorm document to write detailed models.

3. Generate controllers, tests, documents etc. based on models.

Third, run the command:

apig gen

It creates all necessary codes to provide RESTful endpoints of models.

4. Build and run server

Finally, just build as normal go code.

$ go mod init
$ go mod tidy
$ go build -o bin/server

After that just execute the server binary. For the first time, you may want to use AUTOMIGRATE=1 when running the server.

$ AUTOMIGRATE=1 bin/server

When AUTOMIGRATE=1, the db tables are generated automatically. After that, you can run the server just executing the command:

$ bin/server

The server runs at http://localhost:8080.

By default, use the port 8080. If you change the port, set environment variables.

$ PORT=3000 bin/server

The server runs at http://localhost:3000.

Usage

new command

new command tells apig to generate API server skeleton.

$ apig new NAME

gen command

gen command tells apig to generate files (routes, controllers, documents...) from gorm model files you wrote.

You MUST run this command at the directory which was generated by new command.

$ apig gen

API Document

API Documents are generated automatically in docs/ directory in the form of API Blueprint.

docs
├── email.apib
├── index.apib
└── user.apib

Aglio is an API Blueprint renderer. Aglio can be installed by

$ npm install -g aglio

You can generate HTML files and run live preview server.

// html file
$ aglio -i index.apib  -o index.html

// running server on localhost:3000
$ aglio -i index.apib --server

index.apib includes other files in your blueprint.

API server specification

Endpoints

Each resource has 5 RESTful API endpoints. Resource name is written in the plural form.

Endpoint	Description	Example (User resource)
GET /<resources>	List items	GET /users List users
POST /<resources>	Create new item	POST /users Create new user
GET /<resources>/{id}	Retrieve the item	GET /users/1 Get the user which ID is 1
PUT /<resources>/{id}	Update the item	PUT /users/1 Update the user which ID is 1
DELETE /<resources>/{id}	Delete the item	DELETE /users/1 Delete the user which ID is 1

Available URL parameters

GET /<resources> and GET /<resources>/{id}

Parameter	Description	Default	Example
fields=	Fields to receive	All fields	name,emails.address
preloads=	Nested resources to preload	(empty)	emails,profile
pretty=	Prettify JSON response	false	true

GET /<resources> only

Parameter	Description	Default	Example
stream=	Return JSON in streaming format	false	true
q[field_name]=	A unique query parameter for each field for filtering	(empty)	q[id]=1,2,5, q[admin]=true&q[registered]=true
sort=	Retrieves a list in order of priority. + or (none) : ascending. - : descending	(empty)	id, -age, id,-created_at
limit=	Maximum number of items	25	50
page=	Page to receive	1	3
last_id=	Beginning ID of items	(empty)	1
order=	Order of items	desc	asc
v=	API version	(empty)	1.2.0

Data Type

Request

API server accepts the form of JSON or Form.

application/json

$ curl -X POST http://localhost:8080/resources \
       -H "Content-type: application/json" \
       -d '{"field":"value"}'

application/x-www-form-urlencoded

$ curl -X POST http://localhost:8080/users \
       -d 'field=value'

multipart/form-data

$ curl -X POST http://localhost:8080/users \
       -F 'field=value'

Response

Response data type is always application/json.

Pagination

API server supports 2 pagination types.

Offset-based pagination

Retrieve items by specifying page number and the number of items per page.

For example:

http://example.com/api/users?limit=5&page=2

+---------+---------+---------+---------+---------+---------+---------+
| ID: 5   | ID: 6   | ID: 7   | ID: 8   | ID: 9   | ID: 10  | ID: 11  |
+---------+---------+---------+---------+---------+---------+---------+
          |                                                 |
 Page 1 ->|<-------------------- Page 2 ------------------->|<- Page 3

Response header includes Link header.

Link:   <http://example.com/api/users?limit=5&page=3>; rel="next",
        <http://example.com/api/users?limit=5&page=1>; rel="prev"

ID/Time-based pagination

Retrieve items by specifying range from a certain point.

For example:

http://example.com/api/users?limit=5&last_id=100&order=desc

+---------+---------+---------+---------+---------+---------+---------+
| ID: 94  | ID: 95  | ID: 96  | ID: 97  | ID: 98  | ID: 99  | ID: 100 |
+---------+---------+---------+---------+---------+---------+---------+
          |               5 items (ID < 100)                |
          |<------------------------------------------------|

Response header includes Link header.

Link:   <http://example.com/api/users?limit=5&last_id=95&order=desc>; rel="next"

Versioning

API server uses Semantic Versioning for API versioning.

There are 2 methods to specify API version.

Request header

Generally we recommend to include API version in Accept header.

Accept: application/json; version=1.0.0

URL parameter

You can also include API version in URL parameter. This is userful for debug on browser or temporary use,

http://example.com/api/users?v=1.0.0

This method is prior to request header method.

License