Add interface to read body bytes in binding

binding/binding.go

@@ -29,6 +29,13 @@ type Binding interface {
 	Bind(*http.Request, interface{}) error
 }
 
+// BindingBody adds BindBody method to Binding.  BindBody is similar with Bind,
+// but it reads the body from supplied bytes instead of req.Body.
+type BindingBody interface {
+	Binding
+	BindBody([]byte, interface{}) error
+}
+
 // StructValidator is the minimal interface which needs to be implemented in
 // order for it to be used as the validator engine for ensuring the correctness
 // of the reqest. Gin provides a default implementation for this using

context.go

@@ -31,6 +31,7 @@ const (
 	MIMEPlain             = binding.MIMEPlain
 	MIMEPOSTForm          = binding.MIMEPOSTForm
 	MIMEMultipartPOSTForm = binding.MIMEMultipartPOSTForm
+	BodyBytesKey          = "github.com/gin-gonic/gin/bodyBytes"
 )
 
 const abortIndex int8 = math.MaxInt8 / 2
@@ -508,6 +509,30 @@ func (c *Context) ShouldBindWith(obj interface{}, b binding.Binding) error {
 	return b.Bind(c.Request, obj)
 }
 
+// ShouldBindBodyWith is similar with ShouldBindWith, but it stores the request
+// body into the context, and reuse when it is called again.
+//
+// NOTE: This method reads the body before binding.  So you should use
+// ShouldBindWith for better performance if you need to call only once.
+func (c *Context) ShouldBindBodyWith(
+	obj interface{}, bb binding.BindingBody,
+) (err error) {
+	var body []byte
+	if cb, ok := c.Get(BodyBytesKey); ok {
+		if cbb, ok := cb.([]byte); ok {
+			body = cbb
+		}
+	}
+	if body == nil {
+		body, err = ioutil.ReadAll(c.Request.Body)
+		if err != nil {
+			return err
+		}
+		c.Set(BodyBytesKey, body)
+	}
+	return bb.BindBody(body, obj)
+}
+
 // ClientIP implements a best effort algorithm to return the real client IP, it parses
 // X-Real-IP and X-Forwarded-For in order to work properly with reverse-proxies such us: nginx or haproxy.
 // Use X-Forwarded-For before X-Real-Ip as nginx uses X-Real-Ip with the proxy's IP.