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Gin Web Framework

Multipart/Urlencoded binding

ShouldBind automatically detects the Content-Type and binds multipart/form-data or application/x-www-form-urlencoded request bodies into a struct. Use the form struct tag to map form field names to struct fields, and binding:"required" to enforce mandatory fields.

This is commonly used for login forms, registration pages, or any HTML form submission.

package main


import (
  "net/http"


  "github.com/gin-gonic/gin"
)


type LoginForm struct {
  User     string `form:"user" binding:"required"`
  Password string `form:"password" binding:"required"`
}


func main() {
  router := gin.Default()


  router.POST("/login", func(c *gin.Context) {
    var form LoginForm
    // ShouldBind automatically selects the right binding based on Content-Type
    if err := c.ShouldBind(&form); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
      return
    }


    if form.User == "user" && form.Password == "password" {
      c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
    } else {
      c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
    }
  })


  router.Run(":8080")
}

Test it

Terminal window
# Multipart form
curl -X POST http://localhost:8080/login \
  -F "user=user" -F "password=password"
# Output: {"status":"you are logged in"}


# URL-encoded form
curl -X POST http://localhost:8080/login \
  -d "user=user&password=password"
# Output: {"status":"you are logged in"}


# Wrong credentials
curl -X POST http://localhost:8080/login \
  -d "user=wrong&password=wrong"
# Output: {"status":"unauthorized"}


# Missing required field
curl -X POST http://localhost:8080/login \
  -d "user=user"
# Output: {"error":"Key: 'LoginForm.Password' Error:Field validation for 'Password' failed on the 'required' tag"}

See also