How do I bind and validate path params?

[smares]

Reading the documentation for v4, https://echo.labstack.com/guide/binding/ gave me the impression that I can define a struct

type GetPDF struct {
	ID string `param:"id" validate:"required,uuid4"`
}

and then bind it. Given the route /pdf/:id, calling /pdf/cfb8d234-ab46-412d-93ad-a2a7eab1f6f6 gives me a validation error that ID is required. Manually setting req.ID = c.Param("id") before doing the validation works.

#1337 says that binding to path parameters is a v5 feature, but #2333 indicates otherwise. I am using v4.10.2.

What am I doing wrong?

[aldas]

I am trying path params binding this way - and it seems to work.

func main() {
	e := echo.New()
	e.Use(middleware.Logger())

	e.GET("/pdf/:id", func(c echo.Context) error {
		type GetPDF struct {
			ID string `param:"id" validate:"required,uuid4"`
		}
		var payload GetPDF
		if err := c.Bind(&payload); err != nil {
			return c.String(http.StatusBadRequest, "bad request")
		}
		return c.JSON(http.StatusOK, payload)
	})

	if err := e.Start(":8080"); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatal(err)
	}
}

Output from command line:

x@x:~/code$ curl http://localhost:8080/pdf/cfb8d234-ab46-412d-93ad-a2a7eab1f6f6
{"ID":"cfb8d234-ab46-412d-93ad-a2a7eab1f6f6"}

Output from server:

   ____    __
  / __/___/ /  ___
 / _// __/ _ \/ _ \
/___/\__/_//_/\___/ v4.10.2
High performance, minimalist Go web framework
https://echo.labstack.com
____________________________________O/_______
                                    O\
⇨ http server started on [::]:8080
{"time":"2023-05-12T20:03:34.145367182+03:00","id":"","remote_ip":"127.0.0.1","host":"localhost:8080","method":"GET","uri":"/pdf/cfb8d234-ab46-412d-93ad-a2a7eab1f6f6","user_agent":"curl/7.85.0","status":200,"error":"","latency":22413,"latency_human":"22.413µs","bytes_in":0,"bytes_out":46}

[aldas]

same when adding validator

package main

import (
	"errors"
	"github.com/go-playground/validator/v10"
	"github.com/labstack/echo/v4"
	"github.com/labstack/echo/v4/middleware"
	"log"
	"net/http"
)

type CustomValidator struct {
	validator *validator.Validate
}

func (cv *CustomValidator) Validate(i interface{}) error {
	if err := cv.validator.Struct(i); err != nil {
		// Optionally, you could return the error to give each route more control over the status code
		return echo.NewHTTPError(http.StatusBadRequest, err.Error())
	}
	return nil
}

func main() {
	e := echo.New()
	e.Validator = &CustomValidator{validator: validator.New()}

	e.Use(middleware.Logger())

	e.GET("/pdf/:id", func(c echo.Context) error {
		type GetPDF struct {
			ID string `param:"id" validate:"required,uuid4"`
		}
		var payload GetPDF
		if err := c.Bind(&payload); err != nil {
			return c.String(http.StatusBadRequest, "bad request")
		}
		if err := c.Validate(payload); err != nil {
			return err
		}

		return c.JSON(http.StatusOK, payload)
	})

	if err := e.Start(":8080"); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatal(err)
	}
}

output:

x@x:~/code$ curl http://localhost:8080/pdf/cfb8d234-ab46-412d-93ad-a2a7eab1f6f6
{"ID":"cfb8d234-ab46-412d-93ad-a2a7eab1f6f6"}

[smares]

Wondering if it's due to how I implemented validation. The "target" is an interface and not a struct.

func ValidateRequest(c echo.Context, i interface{}) error {
	if err := c.Bind(&i); err != nil {
		return err
	}

	if err := c.Validate(i); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, ...)
	}

	return nil
}

And the handler does handler.ValidateRequest(c, &req). Have to check later.

[smares]

Yes, if I bind directly to the struct, it works.

[aldas]

@smares , you function would work like this

func ValidateRequest(c echo.Context, i interface{}) error {
	if err := c.Bind(i); err != nil { // <-- no '&' here. this is already passed as reference
		return err
	}

	if err := c.Validate(i); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, err.Error())
	}

	return nil
}

and call it as

		if err := ValidateRequest(c, &payload); err != nil {  // <--- dereference is done here
			return err
		}

and full example:

package main

import (
	"errors"
	"github.com/go-playground/validator/v10"
	"github.com/labstack/echo/v4"
	"github.com/labstack/echo/v4/middleware"
	"log"
	"net/http"
)

func ValidateRequest(c echo.Context, i interface{}) error {
	if err := c.Bind(i); err != nil { // <-- no '&' here. this is already passed as reference
		return err
	}

	if err := c.Validate(i); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, err.Error())
	}

	return nil
}

type CustomValidator struct {
	validator *validator.Validate
}

func (cv *CustomValidator) Validate(i interface{}) error {
	if err := cv.validator.Struct(i); err != nil {
		// Optionally, you could return the error to give each route more control over the status code
		return echo.NewHTTPError(http.StatusBadRequest, err.Error())
	}
	return nil
}

func main() {
	e := echo.New()
	e.Validator = &CustomValidator{validator: validator.New()}

	e.Use(middleware.Logger())

	e.GET("/pdf/:id", func(c echo.Context) error {
		type GetPDF struct {
			ID string `param:"id" validate:"required,uuid4"`
		}
		var payload GetPDF
		if err := ValidateRequest(c, &payload); err != nil {
			return err
		}

		return c.JSON(http.StatusOK, payload)
	})

	if err := e.Start(":8080"); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatal(err)
	}
}