aah Data Validation

aah provides well integrated and seamless data validation feature for your application. It could be applied for URL Path Param, Form, JSON and XML.

  • aah internally uses gopkg.in/go-playground/validator.v9 as validator. It’s simple and effective validation library.
  • Upcoming planning to externalize the validation feature so that third-party libraries could be registered into aah.

Validation errors are well integrated with aah error handling mechanism.

Table of Contents

Controller Action Parameters Validation

Action parameter validation applied on struct for Form, JSON, XML and any struct binding. Basically after successful bind on action parameter type struct aah applies the validation.


Basically you have to define Tag validate with rules for the struct fields. Refer to validator documentation.

// User contains user information
type User struct {
	FirstName      string     `validate:"required"`
	LastName       string     `validate:"required"`
	Age            uint8      `validate:"gte=0,lte=130"`
	Email          string     `validate:"required,email"`
	FavouriteColor string     `validate:"iscolor"`                // alias for 'hexcolor|rgb|rgba|hsl|hsla'
	Addresses      []*Address `validate:"required,dive,required"` // a person can have a home and cottage...

// Address houses a users address information
type Address struct {
	Street string `validate:"required"`
	City   string `validate:"required"`
	Planet string `validate:"required"`
	Phone  string `validate:"required"`

// Create method used to create an user.
func (c *UserController) Create(user *User)  {
  // Implementation goes here

// HandleError method called on any errors happens within the user controller.
// More info, read https://docs.aahframework.org/error-handling.html
func (c *UserController) HandleError(e *aah.Error) bool  {
  // handle error
  return true

How to Validate URL Query Parameters

Tip: The best way to validate collective query parameters is to bind those values into struct then aah automatically does validation on struct and gives a result.

Doing it manually for individual values on-demand basics.

Use method aah.App().ValidateValue(value, "rules"). Refer to validator documentation

  • It returns true if validation passed otherwise false.

For example -

i := 15
result := aah.App().ValidateValue(i, "gt=1,lt=10")

emailAddress := "sample@sample"
result := aah.App().ValidateValue(emailAddress, "email")

numbers := []int{23, 67, 87, 23, 90}
result := aah.App().ValidateValue(numbers, "unique")

color := "#e25657"
result := aah.App().ValidateValue(color, "iscolor") // alias for 'hexcolor|rgb|rgba|hsl|hsla'

Adding Custom Validation Functions

All capabilities provided by library gopkg.in/go-playground/validator.v9 to add custom validation function.

To obtain aah validator instance

validator := aah.App().Validator()

// Add your validation funcs

Note: The recommended spot/place to register custom validation functions is at <app-base-dir>/app/init.go file.