Go编写Web服务与操作数据库基本语句

Go 和 Gin Web 框架编写 RESTful Web 服务 API 的基础知识.

package main

import (
    "net/http"

    "github.com/gin-gonic/gin"
)

// album 表示有关专辑的数据.
type album struct {
    ID     string  `json:"id"`
    Title  string  `json:"title"`
    Artist string  `json:"artist"`
    Price  float64 `json:"price"`
}

// 专辑切片以填充专辑数据记录.
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},
}

func main() {
    router := gin.Default()
    router.GET("/albums", getAlbums)
    router.GET("/albums/:id", getAlbumByID)
    router.POST("/albums", postAlbums)

    router.Run("localhost:8080")
}

// getAlbums 以 JSON 格式响应所有专辑的列表.
func getAlbums(c *gin.Context) {
    c.IndentedJSON(http.StatusOK, albums)
}

// postAlbums 从请求体中收到的JSON中添加一个专辑.
func postAlbums(c *gin.Context) {
    var newAlbum album

    // 调用 BindJSON 将收到的 JSON 绑定到
    // newAlbum.
    if err := c.BindJSON(&newAlbum); err != nil {
        return
    }

    // 将新专辑添加到切片.
    albums = append(albums, newAlbum)
    c.IndentedJSON(http.StatusCreated, newAlbum)
}

// getAlbumByID 查找 ID 值与客户端发送的 id
// 参数匹配的专辑,然后返回该专辑作为响应.
func getAlbumByID(c *gin.Context) {
    id := c.Param("id")

    // 循环浏览专辑列表,查找
    // ID 值与参数匹配的专辑.
    for _, a := range albums {
        if a.ID == id {
            c.IndentedJSON(http.StatusOK, a)
            return
        }
    }
    c.IndentedJSON(http.StatusNotFound, gin.H{"message": "album not found"})
}

Go访问关系数据库

package main

import (
	"database/sql"
	"fmt"
	"log"
	"os"

	"github.com/go-sql-driver/mysql"
)

var db *sql.DB

type Album struct {
	ID     int64
	Title  string
	Artist string
	Price  float32
}

func main() {
	// Capture connection properties.
	cfg := mysql.Config{
		User:                 os.Getenv("DBUSER"),
		Passwd:               os.Getenv("DBPASS"),
		Net:                  "tcp",
		Addr:                 "127.0.0.1:3306",
		DBName:               "recordings",
		AllowNativePasswords: true,
	}
	log.Println(cfg.FormatDSN())
	// Get a database handle.
	var err error
	db, err = sql.Open("mysql", cfg.FormatDSN())
	if err != nil {
		log.Fatal(err)
	}

	pingErr := db.Ping()
	if pingErr != nil {
		log.Fatal(pingErr)
	}
	fmt.Println("Connected!")

	albums, err := albumsByArtist("John Coltrane")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Albums found: %v\n", albums)

	// 在此处对 ID 2 进行硬编码以测试查询。
	alb, err := albumByID(2)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Album found: %v\n", alb)

	albID, err := addAlbum(Album{
		Title:  "The Modern Sound of Betty Carter",
		Artist: "Betty Carter",
		Price:  49.99,
	})
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("ID of added album: %v\n", albID)
}

// albumsByArtist对具有指定艺术家姓名的专辑进行查询.
func albumsByArtist(name string) ([]Album, error) {
	// 一个专辑切片,用于保存返回行中的数据.
	var albums []Album

	rows, err := db.Query("SELECT * FROM album WHERE artist = ?", name)
	if err != nil {
		return nil, fmt.Errorf("albumsByArtist %q: %v", name, err)
	}
	defer rows.Close()
	// 遍历行,使用"扫描"将列数据分配给结构字段.
	for rows.Next() {
		var alb Album
		if err := rows.Scan(&alb.ID, &alb.Title, &alb.Artist, &alb.Price); err != nil {
			return nil, fmt.Errorf("albumsByArtist %q: %v", name, err)
		}
		albums = append(albums, alb)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("albumsByArtist %q: %v", name, err)
	}
	return albums, nil
}

// albumByID查询指定ID的专辑。
func albumByID(id int64) (Album, error) {
	// 一个专辑将保存返回行的数据。
	var alb Album

	row := db.QueryRow("SELECT * FROM album WHERE id = ?", id)
	if err := row.Scan(&alb.ID, &alb.Title, &alb.Artist, &alb.Price); err != nil {
		if err == sql.ErrNoRows {
			return alb, fmt.Errorf("albumsById %d: no such album", id)
		}
		return alb, fmt.Errorf("albumsById %d: %v", id, err)
	}
	return alb, nil
}

// addAlbum 将指定的专辑添加到数据库中,
// 返回新条目的专辑 ID
func addAlbum(alb Album) (int64, error) {
	result, err := db.Exec("INSERT INTO album (title, artist, price) VALUES (?, ?, ?)", alb.Title, alb.Artist, alb.Price)
	if err != nil {
		return 0, fmt.Errorf("addAlbum: %v", err)
	}
	id, err := result.LastInsertId()
	if err != nil {
		return 0, fmt.Errorf("addAlbum: %v", err)
	}
	return id, nil
}

官方Documentation

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