go使用Gin web框架开发api入门

gin框架是go语言用于开发web的框架，开发一个api,仍然包含路由、控制器、数据处理、响应返回这么几部分。

1.项目准备

初始化项目

mkdir web-server-gin 
cd web-server-gin

go mod init example/web-server-gin # 初始化模块
touch main.go # 作为入口文件，为简单起见，所有请求和处理都放在这里

main.go 文件内容

// main.go
package main 

import(
    "net/http"
    "github.com/gin-gonic/gin" // 引入我们要的用的gin框架
)

func main() {
}

2. 开始我们第一个api

这里我们以唱片album需求来实现，遵从restful api原则，开发
GET /alubms 获取唱片列表

• 先写入路由

// main.go
package main 

import(
    "net/http"
    "github.com/gin-gonic/gin" // 引入我们要的用的gin框架
)

// 此步骤添加
func main() {
    router := gin.Default()
    router.GET("/albums", getAlbums) // 路由写在这里

    router.Run("localhost:8080")
}

• 补全控制器

// main.go
package main 

import(
    "net/http"
    "github.com/gin-gonic/gin" // 引入我们要的用的gin框架
)

// 此步骤添加
func main() {
    router := gin.Default()
    router.GET("/albums", getAlbums) // 路由写在这里

    router.Run("localhost:8080")
}

// 控制器函数 gin.Context 是框架的上下问
func getAlbums(c *gin.Context) {
    // c.IndentedJSON是返回缩减的json
    c.IndentedJSON(http.StatusOK, albums)
}

// 结构体 ID（字段） String(字段类型)
type album struct {
    ID     string  `json:"id"`
    Title  string  `json:"title"`
    Artist string  `json:"artist"`
    Price  float64 `json:"price"`
}

// 用新的结构体类型 定义一个唱片集合
var albums = []album{
    {ID: "1", Title: "Blue Train", Artist: "John Coltrane", Price: 56.99},
    {ID: "2", Title: "Jeru", Artist: "Gerry Mulligan", Price: 17.99},
    {ID: "3", Title: "Sarah Vaughan and Clifford Brown", Artist: "Sarah Vaughan", Price: 39.99},
}

• 运行

go mod tidy # 运行获取需要用到的依赖,为什么在最终这里执行，不在一开始引入模块的时候执行，目前的理解是，最终才会知道需要用到哪些依赖
go run .    # 运行

在命令行curl http://localhost:8080/albums

 dongmingyan@pro ⮀ ~/go_playground/web-server-gin ⮀ go run .
[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    /albums                   --> main.getAlbums (3 handlers)
[GIN-debug] [WARNING] You trusted all proxies, this is NOT safe. We recommend you to set a value.
Please check https://pkg.go.dev/github.com/gin-gonic/gin#readme-don-t-trust-all-proxies for details.
[GIN-debug] Listening and serving HTTP on localhost:8080
[GIN] 2023/07/10 - 22:34:52 | 200 |     116.705µs |       127.0.0.1 | GET      "/albums"

dongmingyan@pro ⮀ ~ ⮀ curl http://localhost:8080/albums
[
    {
        "id": "1",
        "title": "Blue Train",
        "artist": "John Coltrane",
        "price": 56.99
    },
    {
        "id": "2",
        "title": "Jeru",
        "artist": "Gerry Mulligan",
        "price": 17.99
    },
    {
        "id": "3",
        "title": "Sarah Vaughan and Clifford Brown",
        "artist": "Sarah Vaughan",
        "price": 39.99
    }
]%

2.添加接口 POST /albums创建唱片

• 添加路由

// main.go
   //  main函数中添加
   router.POST("/albums", postAlbums)

• 添加控制器,main.go文件底部添加

// main.go

// 添加条目到albums
func postAlbums(c *gin.Context) {
    // 定义一个变量 为结构体类型album
    var newAlbum album

    // 调用 BindJSON 绑定接受到的json到 newAlbum变量
    if err := c.BindJSON(&newAlbum); err != nil {
            return
    }

    // 将newAlbum 加入到albums中,这里是加到内存中的
    albums = append(albums, newAlbum)
    c.IndentedJSON(http.StatusCreated, newAlbum)
}

• 运行，如果之前是运行的需要先终止掉，重新go run .

dongmingyan@pro ⮀ ~ ⮀ curl http://localhost:8080/albums \
    --include \
    --header "Content-Type: application/json" \
    --request "POST" \
    --data '{"id": "4","title": "The Modern Sound of Betty Carter","artist": "Betty Carter","price": 49.99}'

HTTP/1.1 201 Created
Content-Type: application/json; charset=utf-8
Date: Tue, 11 Jul 2023 13:15:06 GMT
Content-Length: 116

{
    "id": "4",
    "title": "The Modern Sound of Betty Carter",
    "artist": "Betty Carter",
    "price": 49.99
}%

3. 添加GET /albums/:id 接口

• 在main函数中，添加路由

// main.go
router.GET("/albums/:id", getAlbumByID)

• 添加控制器函数

// main.go
func getAlbumByID(c *gin.Context) {
    id := c.Param("id") // 路径参数获取值

    // 循环找到id
    for _, a := range albums {
            if a.ID == id {
                    c.IndentedJSON(http.StatusOK, a)
                    return
            }
    }
    c.IndentedJSON(http.StatusNotFound, gin.H{"message": "album not found"})
}

• 运行，go run .

✘ dongmingyan@pro ⮀ ~/go_playground/web-server-gin ⮀ go run .
[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    /albums                   --> main.getAlbums (3 handlers)
[GIN-debug] POST   /albums                   --> main.postAlbums (3 handlers)
[GIN-debug] GET    /albums/:id               --> main.getAlbumByID (3 handlers)
[GIN-debug] [WARNING] You trusted all proxies, this is NOT safe. We recommend you to set a value.
Please check https://pkg.go.dev/github.com/gin-gonic/gin#readme-don-t-trust-all-proxies for details.
[GIN-debug] Listening and serving HTTP on localhost:8080
[GIN] 2023/07/11 - 21:24:02 | 200 |     108.951µs |       127.0.0.1 | GET      "/albums/3"
[GIN] 2023/07/11 - 21:24:05 | 200 |      74.037µs |       127.0.0.1 | GET      "/albums/1"

dongmingyan@pro ⮀ ~ ⮀ curl http://localhost:8080/albums/1
{
    "id": "1",
    "title": "Blue Train",
    "artist": "John Coltrane",
    "price": 56.99
}%