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.

Validation errors are well integrated with aah error handling mechanism.

Table of Contents

Route Path Param Validation

Defining route path parameter validation is very easy in aah. Refer to validator documentation.



For example -

# User Info

# User Info - Requests
/v1/users/sample@sample.com/addresses => would pass
/v1/users/sample@sample/addresses     => would fail

# Book Info

# Book Info - Requests
/v1/books/978-1-56619-909-4/excerpt  => would pass
/v1/books/dshgdshgdsjhgdshg/excerpt  => would fail

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 (u *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 (u *UserController) HandleError(e *aah.Error) bool  {
  // handle error
  return true

How to Validate URL Query Parameters

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

You have do it manually for individual values on-demand basics. How to do?

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

  • It returns true if validation passed otherwise false.

For example -

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

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

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

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

Adding Your Custom Validation Functions

You can use all capabilities provided by library gopkg.in/go-playground/validator.v9 to add custom validator implementation.

To obtain aah validator instance

validator := aah.Validator()

// Add your validation funcs

Note: The recommended spot/place to register custom validation functions is at init.go file.