Go-Gin read request body many times - go

Question

I am trying to restore the context with it's data after performing validation on it's data.I need the data to keep moving as need it later on in the next function.
I am new to golang and the below code is as far I could go. any help and a better approach is much appreciated.
thanks in advance.
the validation middleware
func SignupValidator(c *gin.Context) {
// Read the Body content
// var bodyBytes []byte
// if c.Request.Body != nil {
// bodyBytes, _ = ioutil.ReadAll(c.Request.Body)
// }
var user entity.User
if err := c.ShouldBindJSON(&user); err != nil {
validate := validator.New()
if err := validate.Struct(&user); err != nil {
c.JSON(http.StatusBadRequest, gin.H{
"error": err.Error(),
})
c.Abort()
return
}
// c.Request.Body = ioutil.NopCloser(bytes.NewBuffer(bodyBytes))
}
// Read the Body content
var bodyBytes []byte
if c.Request.Body != nil {
bodyBytes, _ = ioutil.ReadAll(c.Request.Body)
}
fmt.Println(string(bodyBytes)) // this empty
c.Next()
}
route
auth.POST("login", gin.Logger(), validations.SignupValidator, func(ctx *gin.Context) {
ctx.JSON(200, videoController.Save(ctx))
})

Answer 1

You can try this.
ByteBody, _ := ioutil.ReadAll(c.Request.Body)
c.Request.Body = ioutil.NopCloser(bytes.NewBuffer(ByteBody))
You can then use ByteBody however you want without side-effects on c.Request.Body

Answer 2

Here is an example of reading body twice with ShouldBindBodyWith, check it:
package main
import (
"log"
"net/http"
"github.com/gin-gonic/gin"
"github.com/gin-gonic/gin/binding"
)
type ParamsOne struct {
Username string `json:"username"`
}
type ParamsTwo struct {
Username string `json:"username"`
}
func main() {
r := gin.New()
r.POST("/", func(c *gin.Context) {
var f ParamsOne
// Read ones
if err := c.ShouldBindBodyWith(&f, binding.JSON); err != nil {
log.Printf("%+v", err)
}
log.Printf("%+v", f)
var ff ParamsTwo
if err := c.ShouldBindBodyWith(&ff, binding.JSON); err != nil {
log.Printf("%+v", err)
}
log.Printf("%+v", ff)
c.IndentedJSON(http.StatusOK, f)
})
r.Run(":4000")
}
Output:
$example: ./example
[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
- using env: export GIN_MODE=release
- using code: gin.SetMode(gin.ReleaseMode)
[GIN-debug] POST / --> main.main.func1 (1 handlers)
[GIN-debug] Listening and serving HTTP on :4000
2020/07/05 10:47:03 {Username:somename}
2020/07/05 10:47:03 {Username:somename}

Answer 3

As #Philidor has shown ShouldBindBodyWith should do the trick, in my case I decided to go with something similar to #spehlivan, because of two reasons:
ShouldBindBodyWith requires that the following binds are also ShouldBindBodyWith, it means I need to change all my previous code, which uses c.Bind
You need to explicitly tell to ShouldBindBodyWith the binding type you are trying to do, JSON, Form, ProtoBuf, etc, other binds like c.Bind detects it automatically.
This is what it looks like:
var input models.SomeInput
bodyCopy := new(bytes.Buffer)
// Read the whole body
_, err := io.Copy(bodyCopy, c.Request.Body)
if err != nil {
log.Println(err)
c.JSON(http.StatusBadRequest, gin.H{"error": "Error reading API token"})
c.Abort()
return
}
bodyData := bodyCopy.Bytes()
// Replace the body with a reader that reads from the buffer
c.Request.Body = ioutil.NopCloser(bytes.NewReader(bodyData))
err = c.Bind(&input)
// Some code here...
// Replace the body with a reader that reads from the buffer
c.Request.Body = ioutil.NopCloser(bytes.NewReader(bodyData))
Pay attention I replaced the c.Request.Body twice, for the bind in that code snippet and then at the end, for the next bind, in another place of my code (this snippet is from a middleware, the next bind is called from the controller).
In my case I needed to do this because the API Token is sent in the request body, which I don't recommend, it should be sent in the request header.