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gin将请求体绑定到不同的结构体中

绑定请求体的常规方法使用

c.Request.Body

，并且不能多次调用

type formA struct {
  Foo string `json:"foo" xml:"foo" binding:"required"`
}

type formB struct {
  Bar string `json:"bar" xml:"bar" binding:"required"`
}

func SomeHandler(c *gin.Context) {
  objA := formA{}
  objB := formB{}
  // This c.ShouldBind consumes c.Request.Body and it cannot be reused.
  if errA := c.ShouldBind(&objA); errA == nil {
    c.String(http.StatusOK, `the body should be formA`)
  // Always an error is occurred by this because c.Request.Body is EOF now.
  } else if errB := c.ShouldBind(&objB); errB == nil {
    c.String(http.StatusOK, `the body should be formB`)
  } else {
    ...
  }
}

同样，你能使用

c.ShouldBindBodyWith


func SomeHandler(c *gin.Context) {
  objA := formA{}
  objB := formB{}
  // This reads c.Request.Body and stores the result into the context.
  if errA := c.ShouldBindBodyWith(&objA, binding.JSON); errA == nil {
    c.String(http.StatusOK, `the body should be formA`)
  // At this time, it reuses body stored in the context.
  } else if errB := c.ShouldBindBodyWith(&objB, binding.JSON); errB == nil {
    c.String(http.StatusOK, `the body should be formB JSON`)
  // And it can accepts other formats
  } else if errB2 := c.ShouldBindBodyWith(&objB, binding.XML); errB2 == nil {
    c.String(http.StatusOK, `the body should be formB XML`)
  } else {
    ...
  }
}

• 
c.ShouldBindBodyWith

  在绑定之前将body存储到上下文中，这对性能有轻微影响，因此如果你要立即调用，则不应使用此方法
• 此功能仅适用于这些格式 —
  
JSON

  ,
  
XML

  ,
  
MsgPack

  ,
  
ProtoBuf

  。对于其他格式，
  
Query

  ,
  
Form

  ,
  
FormPost

  ,
  
FormMultipart

  , 可以被
  
c.ShouldBind()

  多次调用而不影响性能