如何使用 Gin 和 Gorm 搭建一个简单的 API 服务 （二）

创建 API

  我们之前已经跑过 Gin 框架的代码，现在是时候加些功能进去了。

读取全部信息

  我们先从＂增删改查＂中的＂查＂入手，查询我们之前添加的信息。我接下来要删除几行代码，并把 Gin 的框架代码加回来。

package main

import (
        "fmt"
        "github.com/gin-gonic/gin"
        "github.com/jinzhu/gorm"
        _ "github.com/jinzhu/gorm/dialects/sqlite"
)

var db *gorm.DB
var err error

type Person struct {
        ID        uint   `json:"id”`
        FirstName string `json:"firstname”`
        LastName  string `json:"lastname”`
}

func main() {
        // NOTE: See we’re using = to assign the global var
        // instead of := which would assign it only in this function
        db, err = gorm.Open("sqlite3", "./gorm.db")
        if err != nil {
                fmt.Println(err)
        }
        defer db.Close()
        db.AutoMigrate(&Person{})
        r := gin.Default()
        r.GET("g/", GetProjects)
        r.Run("g:8080")
}

func GetProjects(c *gin.Context) {
        var people []Person
        if err := db.Find(&people).Error; err != nil {
                c.AbortWithStatus(404)
                fmt.Println(err)
        } else {
                c.JSON(200, people)
        }
}

  那么运行程序，并在浏览器中访问 http://localhost:8080，你应该看到：

[{“id”: 1,”firstname”: “John”,”lastname”: “Doe”}]

  喔，几行代码我们就可以拿到 API 服务器的响应了，而且大部分代码都是用来错误处理的。

读取特定信息

  好，为了把 API 接口写的更符合 REST 规范，我们加入查询特定信息的借口

package main

import (
    "fmt"
    "github.com/gin-gonic/gin"
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/sqlite"
)

var db *gorm.DB
var err error

type Person struct {
    ID        uint   `json:"id”`
    FirstName string `json:"firstname”`
    LastName  string `json:"lastname”`
}

func main() {
    // NOTE: See we’re using = to assign the global var
    // instead of := which would assign it only in this function
    db, err = gorm.Open("sqlite3", "./gorm.db")
    if err != nil {
        fmt.Println(err)
    }
    defer db.Close()
    db.AutoMigrate(&Person{})
    r := gin.Default()

    r.GET("g/", GetProjects)
    r.GET("/people/:id", GetPerson)

    r.Run("g:8080")
}

func GetProjects(c *gin.Context) {
    var people []Person
    if err := db.Find(&people).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, people)
    }
}

func GetPerson(c *gin.Context) {
    id := c.Params.ByName("id")
    var person Person
    if err := db.Where("id = ?", id).First(&person).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, person)
    }
}

  现在运行程序，但请注意，如果要访问全部信息，你需要访问的地址变成了 http://localhost:8080/people/ ，如果 在 URL 的末尾加入了 ID，你就会得到特定的信息 http://localhost:8080/people/1

{"id": 1, "firstname": "John", "lastname": "Doe"}

添加信息

  只有一条记录是看不大出来查询全部信息和查询单条信息的区别的，所以咱们来把添加信息的功能加上吧。

package main

import (
    "fmt"
    "github.com/gin-gonic/gin"
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/sqlite"
)

var db *gorm.DB
var err error

type Person struct {
    ID        uint   `json:"id”`
    FirstName string `json:"firstname”`
    LastName  string `json:"lastname”`
}

func main() {
    // NOTE: See we’re using = to assign the global var
    // instead of := which would assign it only in this function
    db, err = gorm.Open("sqlite3", "./gorm.db")
    if err != nil {
        fmt.Println(err)
    }
    defer db.Close()
    db.AutoMigrate(&Person{})
    r := gin.Default()

    r.GET("g/", GetProjects)
    r.GET("/people/:id", GetPerson)
    r.POST("/people", CreatePerson)

    r.Run("g:8080")
}

func GetProjects(c *gin.Context) {
    var people []Person
    if err := db.Find(&people).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, people)
    }
}

func GetPerson(c *gin.Context) {
    id := c.Params.ByName("id")
    var person Person
    if err := db.Where("id = ?", id).First(&person).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, person)
    }
}

func CreatePerson(c *gin.Context) {
    var person Person
    c.BindJSON(&person)
    db.Create(&person)
    c.JSON(200, person)
}

  接下来让我们从终端运行 curl 命令测试一下新加的功能是不是可用，当然还是先要把程序运行起来。
  在终端运行：

$ curl -i -X POST http://localhost:8080/people -d '{ "FirstName": "Elvis", "LastName": "Presley"}'

  应该会看到成功的响应消息：

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Date: Sat, 03 Dec 2016 00:14:06 GMT
Content-Length: 50
{"id":2,"firstname":"Elvis","lastname":"Presley"}

  现在我们访问一下查询全部信息的接口，http://localhost:8080/people/

[{"id": 1,"firstname": "John","lastname": "Doe"},{"id": 2,"firstname": "Elvis","lastname": "Presley"}]

  太棒啦，代码没问题。这回我们只发送 Person 结构体的部分信息，看看程序会如何处理。

$ curl -i -X POST http://localhost:8080/people -d '{ "FirstName": "Madison"}'

  刷新一下浏览器，发现只添加了我们发送的信息。

[{"id": 1,"firstname": "John","lastname": "Doe"},{"id": 2,"firstname": "Elvis","lastname": "Presley"},{"id": 3,"firstname": "Madison","lastname": ""}]

  这就是 Gin 如何工作的了，留意一下 c.BindJSON(&person) 这行，它会自动匹配请求消息中的数据信息。
  虽然请求消息里可能缺某些信息，就比如刚才那个例子，而且大小写不匹配也没有关系，Gin 的容错性非常高。非常简单！

更新信息

  我们不能把 Madison 这条记录没有姓氏啊，是时候加入更新功能了。

package main

import (
    "fmt"
    "github.com/gin-gonic/gin"
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/sqlite"
)

var db *gorm.DB
var err error

type Person struct {
    ID        uint   `json:"id"`
    FirstName string `json:"firstname"`
    LastName  string `json:"lastname"`
}

func main() {
    // NOTE: See we're using = to assign the global var
    // instead of := which would assign it only in this function
    db, err = gorm.Open("sqlite3", "./gorm.db")
    if err != nil {
        fmt.Println(err)
    }
    defer db.Close()
    db.AutoMigrate(&Person{})
    r := gin.Default()

    r.GET("g/", GetProjects)
    r.GET("/people/:id", GetPerson)
    r.POST("/people", CreatePerson)
    r.PUT("/people/:id", UpdatePerson)

    r.Run("g:8080")
}

func GetProjects(c *gin.Context) {
    var people []Person
    if err := db.Find(&people).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, people)
    }
}

func GetPerson(c *gin.Context) {
    id := c.Params.ByName("id")
    var person Person
    if err := db.Where("id = ?", id).First(&person).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, person)
    }
}

func CreatePerson(c *gin.Context) {
    var person Person
    c.BindJSON(&person)
    db.Create(&person)
    c.JSON(200, person)
}

func UpdatePerson(c *gin.Context) {
    var person Person
    id := c.Params.ByName("id")
    if err := db.Where("id = ?", id).First(&person).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    }
    c.BindJSON(&person)
    db.Save(&person)
    c.JSON(200, person)
}

  这次我们用类似的 curl 命令 进行测试，但不同的是用 PUT 方法，而且是用在特定的信息上。

$ curl -i -X PUT http://localhost:8080/people/3 -d '{ "FirstName": "Madison", "LastName":"Sawyer" }'
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Date: Sat, 03 Dec 2016 00:25:35 GMT
Content-Length: 51
{"id":3,"firstname":"Madison","lastname":"Sawyer"}

  当然更新浏览器后，我们就可以看见 "sawyer" 添加到了 "LastName" 一栏里。

[{"id": 1,"firstname": "John","lastname": "Doe"},{"id": 2,"firstname": "Elvis","lastname": "Presley"},{"id": 3,"firstname": "Madison","lastname": "Sawyer"}]

  这次我们只更新 "FirstName" 字段试试。

$ curl -i -X PUT http://localhost:8080/people/3 -d '{ "FirstName": "Tom" }'

  显示如下

[{"id": 1,"firstname": "John","lastname": "Doe"},{"id": 2,"firstname": "Elvis","lastname": "Presley"},{"id": 3,"firstname": "Tom","lastname": "Sawyer"}]

删除

  这次轮到删除功能了

package main

import (
    "fmt"
    "github.com/gin-gonic/gin"
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/sqlite"
)

var db *gorm.DB
var err error

type Person struct {
    ID        uint   `json:"id"`
    FirstName string `json:"firstname"`
    LastName  string `json:"lastname"`
}

func main() {
    // NOTE: See we're using = to assign the global var
    // instead of := which would assign it only in this function
    db, err = gorm.Open("sqlite3", "./gorm.db")
    if err != nil {
        fmt.Println(err)
    }
    defer db.Close()
    db.AutoMigrate(&Person{})
    r := gin.Default()

    r.GET("g/", GetProjects)
    r.GET("/people/:id", GetPerson)
    r.POST("/people", CreatePerson)
    r.PUT("/people/:id", UpdatePerson)
    r.DELETE("/people/:id", DeletePerson)

    r.Run("g:8080")
}

func GetProjects(c *gin.Context) {
    var people []Person
    if err := db.Find(&people).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, people)
    }
}

func GetPerson(c *gin.Context) {
    id := c.Params.ByName("id")
    var person Person
    if err := db.Where("id = ?", id).First(&person).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, person)
    }
}

func CreatePerson(c *gin.Context) {
    var person Person
    c.BindJSON(&person)
    db.Create(&person)
    c.JSON(200, person)
}

func UpdatePerson(c *gin.Context) {
    var person Person
    id := c.Params.ByName("id")
    if err := db.Where("id = ?", id).First(&person).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    }
    c.BindJSON(&person)
    db.Save(&person)
    c.JSON(200, person)
}

func DeletePerson(c *gin.Context) {
    id := c.Params.ByName("id")
    var person Person
    d := db.Where("id = ?", id).Delete(&person)
    fmt.Println(d)
    c.JSON(200, gin.H{"id #" + id: "deleted"})
}

  我们用 curl 的 Delete 方法测试一下

$ curl -i -X DELETE http://localhost:8080/people/1

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Date: Sat, 03 Dec 2016 00:32:40 GMT
Content-Length: 20

{"id #1":"deleted"}

  刷新浏览器，John Doe 这条记录已经删掉了。

[{"id": 2,"firstname": "Elvis","lastname": "Presley"},{"id": 3,"firstname": "Tom","lastname": "Sawyer"}]

 

 

 

 

作者：blackpiglet
链接：https://www.jianshu.com/p/443766f0e796
来源：简书
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