Model JSON binding and validation

• Type
  • Must bind : 바인딩 에러가 있을 경우, 400 에러 및 에러난 바인딩 타입 response (text/plain)
  • Should bind : 바인딩 에러가 있을 경우, 에러 리턴 → 에러 핸들링

// Binding from JSON
type Login struct {
	User     string `json:"user" binding:"required"`
	Password string `json:"password" binding:"required"`
}

router.POST("/loginJSON", func(c *gin.Context) {
	var json Login
	if err := c.ShouldBindJSON(&json); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
})

{"error":"Key: 'Login.Password' Error:Field validation for 'Password' failed on the 'required' tag"}

• Skip validate
  • binding:"-”

Custom Validator

// Booking contains binded and validated data.
type Booking struct {
	CheckIn  time.Time `form:"check_in" binding:"required,bookabledate" time_format:"2006-01-02"`
	CheckOut time.Time `form:"check_out" binding:"required,gtfield=CheckIn" time_format:"2006-01-02"`
}

var bookableDate validator.Func = func(fl validator.FieldLevel) bool {
	date, ok := fl.Field().Interface().(time.Time)
	if ok {
		today := time.Now()
		if today.After(date) {
			return false
		}
	}
	return true
}

func main() {
	route := gin.Default()
	
	if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
		v.RegisterValidation("bookabledate", bookableDate)
	}
	
	route.GET("/bookable", getBookable)
	route.Run(":8085")
}

func getBookable(c *gin.Context) {
	var b Booking
	if err := c.ShouldBindWith(&b, binding.Query); err == nil {
		c.JSON(http.StatusOK, gin.H{"message": "Booking dates are valid!"})
	} else {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
	}
}

Bind Query String

type Person struct {
        Name       string    `form:"name"`
        Address    string    `form:"address"`
        Birthday   time.Time `form:"birthday" time_format:"2006-01-02" time_utc:"1"`
        CreateTime time.Time `form:"createTime" time_format:"unixNano"`
        UnixTime   time.Time `form:"unixTime" time_format:"unix"`
}

func startPage(c *gin.Context) {
	var person Person
	// If `GET`, only `Form` binding engine (`query`) used.
	// If `POST`, first checks the `content-type` for `JSON` or `XML`, then uses `Form` (`form-data`).
	// See more at <https://github.com/gin-gonic/gin/blob/master/binding/binding.go#L88>
        if c.ShouldBind(&person) == nil {
                log.Println(person.Name)
                log.Println(person.Address)
                log.Println(person.Birthday)
                log.Println(person.CreateTime)
                log.Println(person.UnixTime)
        }

	c.String(http.StatusOK, "Success")
}

$ curl -X GET "localhost:8085/testing?name=appleboy&address=xyz&birthday=1992-03-15&createTime=1562400033000000123&unixTime=1562400033"

Bind Uri

type Person struct {
	ID string `uri:"id" binding:"required,uuid"`
	Name string `uri:"name" binding:"required"`
}

func main() {
	route := gin.Default()
	route.GET("/:name/:id", func(c *gin.Context) {
		var person Person
		if err := c.ShouldBindUri(&person); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"msg": err.Error()})
			return
		}
		c.JSON(http.StatusOK, gin.H{"name": person.Name, "uuid": person.ID})
	})
	route.Run(":8088")
}

Bind Header

type testHeader struct {
	Rate   int    `header:"Rate"`
	Domain string `header:"Domain"`
}

func main() {
	r := gin.Default()
	r.GET("/", func(c *gin.Context) {
		h := testHeader{}

		if err := c.ShouldBindHeader(&h); err != nil {
			c.JSON(http.StatusOK, err)
		}

		fmt.Printf("%#v\\n", h)
		c.JSON(http.StatusOK, gin.H{"Rate": h.Rate, "Domain": h.Domain})
	})

	r.Run()

// client
// curl -H "rate:300" -H "domain:music" 127.0.0.1:8080/
// output
// {"Domain":"music","Rate":300}
}