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（参考 [#1341](https://github.com/gin-gonic/gin/pull/1341)）