Try to bind body into different structs

The normal methods for binding request body consumes c.Request.Body and they cannot be called multiple times.

  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.   } else if errB := c.ShouldBind(&objB); errB == nil {
  17.     c.String(http.StatusOK, `the body should be formB`)
  18.   } else {
  19.     ...
  20.   }
  21. }

For this, you can use c.ShouldBindBodyWith.

  1. func SomeHandler(c *gin.Context) {
  2.   objA := formA{}
  3.   objB := formB{}
  4.   // This reads c.Request.Body and stores the result into the context.
  5.   if errA := c.ShouldBindBodyWith(&objA, binding.JSON); errA == nil {
  6.     c.String(http.StatusOK, `the body should be formA`)
  7.   // At this time, it reuses body stored in the context.
  8.   } else if errB := c.ShouldBindBodyWith(&objB, binding.JSON); errB == nil {
  9.     c.String(http.StatusOK, `the body should be formB JSON`)
  10.   // And it can accepts other formats
  11.   } else if errB2 := c.ShouldBindBodyWith(&objB, binding.XML); errB2 == nil {
  12.     c.String(http.StatusOK, `the body should be formB XML`)
  13.   } else {
  14.     ...
  15.   }
  16. }
  • c.ShouldBindBodyWith stores body into the context before binding. This has a slight impact to performance, so you should not use this method if you are enough to call binding at once.
  • This feature is only needed for some formats – JSON, XML, MsgPack, ProtoBuf. For other formats, Query, Form, FormPost, FormMultipart, can be called by c.ShouldBind() multiple times without any damage to performance (See #1341).

Last modified March 7, 2020 : add blog dir (#115) (f46734b)