Request

A handler reads request data through the echo.Context. Echo can retrieve values individually by name, bind them into structs (see Binding), and hand off validation to a validator you register.

Retrieve data

Form data

Retrieve a form field by name with Context#FormValue(name string):

e.POST("/form", func(c *echo.Context) error {
  name := c.FormValue("name")
  return c.String(http.StatusOK, name)
})

For types other than string, use the generic echo.FormValue[T] function:

age, err := echo.FormValue[int](c, "age")
if err != nil {
  return err
}

Test with:

curl -X POST http://localhost:1323/form -d 'name=Joe&age=30'

To bind a custom data type, implement the echo.BindUnmarshaler interface:

type Timestamp time.Time

func (t *Timestamp) UnmarshalParam(src string) error {
  ts, err := time.Parse(time.RFC3339, src)
  if err != nil {
    return err
  }
  *t = Timestamp(ts)
  return nil
}

Query parameters

Retrieve a query parameter by name with Context#QueryParam(name string):

func(c *echo.Context) error {
  name := c.QueryParam("name")
  return c.String(http.StatusOK, name)
}

For types other than string, use the generic echo.QueryParam[T] function:

age, err := echo.QueryParam[int](c, "age")
if err != nil {
  return err
}

curl -X GET "http://localhost:1323?name=Joe&age=30"

Path parameters

Retrieve a registered path parameter by name with Context#Param(name string):

e.GET("/users/:name", func(c *echo.Context) error {
  name := c.Param("name")
  return c.String(http.StatusOK, name)
})

For types other than string, use the generic echo.PathParam[T] function:

id, err := echo.PathParam[int](c, "id")
if err != nil {
  return err
}

curl http://localhost:1323/users/Joe
curl http://localhost:1323/users/123

Binding data

Echo can also bind request data into native Go structs and variables. See Binding.

Validate data

Echo has no built-in data validation. You can register a custom validator via Echo#Validator and use a third-party library such as go-playground/validator.

The example below validates a bound struct:

package main

import (
  "net/http"

  "github.com/go-playground/validator/v10" // go get github.com/go-playground/validator/v10
  "github.com/labstack/echo/v5"
)

type CustomValidator struct {
  validator *validator.Validate
}

func (cv *CustomValidator) Validate(i any) error {
  if err := cv.validator.Struct(i); err != nil {
    // Optionally return the error to let each route control the status code.
    return echo.ErrBadRequest.Wrap(err)
  }
  return nil
}

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

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

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

  if err := e.Start(":1323"); err != nil {
    e.Logger.Error("failed to start server", "error", err)
  }
}

curl -X POST http://localhost:1323/users \
  -H 'Content-Type: application/json' \
  -d '{"name":"Joe","email":"joe@invalid-domain"}'
{"message":"Key: 'User.Email' Error:Field validation for 'Email' failed on the 'email' tag"}