Gin框架-模型绑定和验证

若要将请求主体绑定到结构体中,请使用模型绑定,目前支持JSON、XML、YAML和标准表单值(foo=bar&boo=baz)的绑定。

Gin使用 go-playground/validator.v8 验证参数,查看完整文档

需要在绑定的字段上设置tag,比如,绑定格式为json,需要这样设置 json:"fieldname"

此外,Gin还提供了两套绑定方法:

  • Must bind
    • Methods – Bind, BindJSON, BindXML, BindQuery, BindYAML
    • Behavior – 这些方法底层使用 MustBindWith,如果存在绑定错误,请求将被以下指令中止 c.AbortWithError(400, err).SetType(ErrorTypeBind),响应状态代码会被设置为400,请求头Content-Type被设置为text/plain; charset=utf-8。注意,如果你试图在此之后设置响应代码,将会发出一个警告 [GIN-debug] [WARNING] Headers were already written. Wanted to override status code 400 with 422,如果你希望更好地控制行为,请使用ShouldBind相关的方法
  • Should bind
    • Methods – ShouldBind, ShouldBindJSON, ShouldBindXML, ShouldBindQuery, ShouldBindYAML
    • Behavior – 这些方法底层使用 ShouldBindWith,如果存在绑定错误,则返回错误,开发人员可以正确处理请求和错误。

当我们使用绑定方法时,Gin会根据Content-Type推断出使用哪种绑定器,如果你确定你绑定的是什么,你可以使用MustBindWith或者BindingWith

你还可以给字段指定特定规则的修饰符,如果一个字段用binding:"required"修饰,并且在绑定时该字段的值为空,那么将返回一个错误。

// 绑定为json
type Login struct {
    User     string `form:"user" json:"user" xml:"user"  binding:"required"`
    Password string `form:"password" json:"password" xml:"password" binding:"required"`
}

func main() {
    router := gin.Default()

    // Example for binding JSON ({"user": "manu", "password": "123"})
    router.POST("/loginJSON", func(c *gin.Context) {
        var json Login
        if err := c.ShouldBindJSON(&json); err != nil {
            c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
            return
        }
        
        if json.User != "manu" || json.Password != "123" {
            c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
            return
        } 
        
        c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
    })

    // Example for binding XML (
    //  <?xml version="1.0" encoding="UTF-8"?>
    //  <root>
    //      <user>user</user>
    //      <password>123</password>
    //  </root>)
    router.POST("/loginXML", func(c *gin.Context) {
        var xml Login
        if err := c.ShouldBindXML(&xml); err != nil {
            c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
            return
        }
        
        if xml.User != "manu" || xml.Password != "123" {
            c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
            return
        } 
        
        c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
    })

    // Example for binding a HTML form (user=manu&password=123)
    router.POST("/loginForm", func(c *gin.Context) {
        var form Login
        // This will infer what binder to use depending on the content-type header.
        if err := c.ShouldBind(&form); err != nil {
            c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
            return
        }
        
        if form.User != "manu" || form.Password != "123" {
            c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
            return
        } 
        
        c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
    })

    // Listen and serve on 0.0.0.0:8080
    router.Run(":8080")
}

请求示例:

$ curl -v -X POST \
  http://localhost:8080/loginJSON \
  -H 'content-type: application/json' \
  -d '{ "user": "manu" }'
> POST /loginJSON HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.51.0
> Accept: */*
> content-type: application/json
> Content-Length: 18
>
* upload completely sent off: 18 out of 18 bytes
< HTTP/1.1 400 Bad Request
< Content-Type: application/json; charset=utf-8
< Date: Fri, 04 Aug 2017 03:51:31 GMT
< Content-Length: 100
<
{"error":"Key: 'Login.Password' Error:Field validation for 'Password' failed on the 'required' tag"}

跳过验证:

当使用上面的curl命令运行上面的示例时,返回错误,因为示例中Password字段使用了binding:"required",如果我们使用binding:"-",那么它就不会报错。

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