两种绑定方法

Must bind

存在绑定错误，请求将被中止
Bind(Content-Type推断出使用哪种绑定器), BindJSON, BindXML, BindQuery, BindYAML

Should bind

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。
ShouldBind(Content-Type推断出使用哪种绑定器), ShouldBindJSON, ShouldBindXML, ShouldBindQuery, ShouldBindYAML

  1. /* 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。form是绑定查询参数
  2. form:"user"   绑定查询参数
  3. json:"user"   绑定json
  4. xml:"user"    绑定xml
  5. uri:"user"    绑定路径参数
  6. header:"user" 绑定header
  8. 绑定Multipart/Urlencoded
  9. File *multipart.FileHeader `form:"file"`
  10. */
  11. type Login struct {
  12.     User     string `form:"user" json:"user" xml:"user"  binding:"required"`
  13.     Password string `form:"password" json:"password" xml:"password" binding:"required"`
  14. }
  15. //实例
  16. var form Login
  17. c.ShouldBind(&form)

一个接口接受不同格式的body

  1. type formA struct {
  2.   Foo string `json:"foo" xml:"foo" binding:"required"`
  3. }
  5. type formB struct {
  6.   Bar string `json:"bar" xml:"bar" binding:"required"`
  7. }
  9. func SomeHandler(c *gin.Context) {
  10.   objA := formA{}
  11.   objB := formB{}
  12.   // This c.ShouldBind consumes c.Request.Body and it cannot be reused.
  13.   if errA := c.ShouldBind(&objA); errA == nil {
  14.     c.String(http.StatusOK, `the body should be formA`)
  15.   // Always an error is occurred by this because c.Request.Body is EOF now.
  16.   // 这样写会报错c.Request.Body is EOF,所以应该采用下面的方法
  17.   } else if errB := c.ShouldBind(&objB); errB == nil {
  18.     c.String(http.StatusOK, `the body should be formB`)
  19.   } else {
  20.     ...
  21.   }
  22. }

注意： c.Request.Body 只能被读取一次，二次读取会失败