echo.Context.Bind() not work in a simple demo

[f5i23q999d]

My code are here:

package main

import (
	"fmt"
	"net/http"

	"github.com/labstack/echo/v4"
)

type User struct {
	Name  string `json:"name"`
	Email string `json:"email"`
}

func main() {
	e := echo.New()

	e.POST("/users", func(c echo.Context) error {


		name := c.QueryParam("name")
		email := c.QueryParam("email")
		fmt.Printf("%s ||| %s \n",name,email)

		u := new(User)
		if err := c.Bind(u); err != nil {
			fmt.Println("Error: ", err)
			return err
		}

		//No output here
		fmt.Printf("%s ---%s \n",u.Name,u.Email)
		return c.JSON(http.StatusCreated, u)
	
	})
	e.Logger.Fatal(e.Start(":1324"))
}

input use Postman and the result:

input with curl and the result:

GO version: 1.17.3

It seems the Bind() function doesn't work and really make me confused.

[aldas]

please add code as text form.

type User struct {
	Name  string `json:"name"`
	Email string `json:"email"`
}

func main() {
	e := echo.New()

	e.POST("/users", func(c echo.Context) (err error) {
		u := new(User)
		if err = c.Bind(u); err != nil {
			return err
		}
		return c.JSON(http.StatusCreated, u)
	})

	log.Fatal(e.Start(":8080"))
}

curl -v -H 'Content-Type: application/json' -d '{"name":"Joe","email":"joe@labstack"}' http://localhost:8080/users

Output:

x@x:~/code/$ curl -v -H 'Content-Type: application/json' \
  -d '{"name":"Joe","email":"joe@labstack"}' \
  http://localhost:8080/users
*   Trying 127.0.0.1:8080...
* Connected to localhost (127.0.0.1) port 8080 (#0)
> POST /users HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.74.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 37
> 
* upload completely sent off: 37 out of 37 bytes
* Mark bundle as not supporting multiuse
< HTTP/1.1 201 Created
< Content-Type: application/json; charset=UTF-8
< Date: Tue, 28 Dec 2021 14:18:36 GMT
< Content-Length: 38
< 
{"name":"Joe","email":"joe@labstack"}
* Connection #0 to host localhost left intact

[f5i23q999d]

Still not work.

D:\Kiux\Golearning\echo2>curl -v -H 'Content-Type: application/json' -d '{"name":"Joe","email":"joe@labstack"}' http://localhost:2323/users
* Could not resolve host: application
* Closing connection 0
curl: (6) Could not resolve host: application
*   Trying ::1:2323...
* Connected to localhost (::1) port 2323 (#1)
> POST /users HTTP/1.1
> Host: localhost:2323
> User-Agent: curl/7.71.1
> Accept: */*
> Content-Length: 31
> Content-Type: application/x-www-form-urlencoded
>
* upload completely sent off: 31 out of 31 bytes
* Mark bundle as not supporting multiuse
< HTTP/1.1 201 Created
< Content-Type: application/json; charset=UTF-8
< Date: Tue, 28 Dec 2021 14:33:42 GMT
< Content-Length: 23
<
{"name":"","email":""}
* Connection #1 to host localhost left intact

[aldas]

Note: in your Postman example you are sending values as Query params (these are from url) and empty body?

c.Bind() binds query params along with body only with get/delete methods. Documentations mentions that https://echo.labstack.com/guide/binding/

You can bind body and query separately but know that - if body has empty fields it will empty fields that query has bound. ie. overwrite data that BindQueryParams had filled (this is how standard library json unmarshaller works)

		if err := (&echo.DefaultBinder{}).BindQueryParams(c, u); err != nil {
			return err
		}
		if err := (&echo.DefaultBinder{}).BindBody(c, u); err != nil {
			return err
		}

ps. you need to add struct tags for query params also

type User struct {
	Name  string `json:"name" query:"name"`
	Email string `json:"email" query:"email"`
}

Also see the difference of these requests

curl -v -H 'Content-Type: application/json'   -d '{"name":"Joe"}' "http://localhost:8080/users?name=test&email=test1"

{"name":"Joe","email":"test1"}

vs

curl -v -H 'Content-Type: application/json'   -d '{"name":"Joe","email":""}' "http://localhost:8080/users?name=test&email=test1"
{"name":"Joe","email":""}

type User struct {
	Name  string `json:"name" query:"name"`
	Email string `json:"email" query:"email"`
}

func main() {
	e := echo.New()

	e.POST("/users", func(c echo.Context) error {

		name := c.QueryParam("name")
		email := c.QueryParam("email")
		fmt.Printf("%s ||| %s \n", name, email)

		u := new(User)
		if err := (&echo.DefaultBinder{}).BindQueryParams(c, u); err != nil {
			return err
		}
		if err := (&echo.DefaultBinder{}).BindBody(c, u); err != nil {
			return err
		}

		//No output here
		fmt.Printf("%s ---%s \n", u.Name, u.Email)
		return c.JSON(http.StatusCreated, u)

	})
	e.Logger.Fatal(e.Start(":8080"))
}

[f5i23q999d]

Your answer make me deep into the details to find out why this happened.

Finally, I find the inappropriate use in Postman that I do not put the content in body but query params. I carefully compare the output of your curl output with my curl output, and I found that the Content-Type in the request header is "application/x-www-form-urlencoded" but not "application/json". I think this is the reason why things do not work in my computer but with the same command. I tried the new version of curl in Windows, but it acts the same, maybe just works in Linux?

Anyway, it's ok to use Postman, thank you so much.

[aldas]

You are putting values to Postman "Params" tab - I think Postman assumes from POST + params that you are trying to simulate form submission and therefore uses "application/x-www-form-urlencoded" as content type.

I do not know what "business requirement" is behind your tests but if you want to simulate Fetch/XHR (ala REST call) Post then use "Body" tab for values in Postman.

See:

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/POST
• https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch