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Validators ensure that field input is entered in correct format and length. For example, you can validate that an email address adheres to a syntax such as first.last@company.com. You can add multiple validators to a field. The validators are executed like a chain, one after the other.

Common validator properties

Simple validator definition:

form:
  tabs:
    - name: tabUser
      label: User info
      fields:
        - name: emailAddress
          class: info.magnolia.ui.form.field.definition.TextFieldDefinition
          label: Email
          validators:
            - name: email
              class: info.magnolia.ui.form.validator.definition.EmailValidatorDefinition
              errorMessage: Enter a valid email address
Node nameValue

 form

 

 tabs

 

 tabUser

 

 fields

 

 emailAddress

 

 validators

 

 email

 

 class

info.magnolia.ui.form.validator.definition.EmailValidatorDefinition

 errorMessage

Enter a valid email address

 class

info.magnolia.ui.form.field.definition.TextFieldDefinition

 label

Email

Properties:

<field name>Name of field.

validators

required

Contains the validator definition.

<validator name>

required

Arbitrary node name. Use a name that describes the validator type.

class

required

Validator definition class. Use the fully-qualified class name.

factoryClass

optional

Fully qualified name of the Java class that creates the validator. The class must implement FieldValidatorFactory . Validator definitions specify a default factory class, meaning that unless you want to use a custom implementation you don't need to configure a factory class.

errorMessage

optional

Text displayed to the user on invalid input. Text string or message bundle key.

i18nBasename

optional

Message bundle for localized messages. This property can be set at dialog, form, tab or field level.

pattern

required for regex validation

Regular expression pattern when using the  info.magnolia.ui.form.validator.definition.RegexpValidatorDefinition class

List of validator definition classes

info.magnolia.ui.form.validator.definition.RegexpValidatorDefinition

Validates a regular expression given in the pattern property.

info.magnolia.ui.form.validator.definition.EmailValidatorDefinition

Validates an email address. Delegates to a Vaadin EmailValidator .

Custom regular expressions

The easiest custom validator is a regular expression. Use the RegexpValidatorDefinition class and define your own regular expression in the pattern property.

Here is an example of validating a ZIP code (U.S. postal code).

form:
  tabs:
    - name: tabUser
      label: User info
      fields:
        - name: zipCode
          class: info.magnolia.ui.form.field.definition.TextFieldDefinition
          label: Zip code
          validators:
            - name: zip
              class: info.magnolia.ui.form.validator.definition.RegexpValidatorDefinition
              pattern: ^\d{5}(-\d{4})?$
              errorMessage: Enter a valid U.S. ZIP code using the format 12345 or 12345-1234
Node nameValue

 form

 

 tabs

 

 tabUser

 

 fields

 

 zipCode

 

 validators

 

 zip

 

 class

info.magnolia.ui.form.validator.definition.RegexpValidatorDefinition

 errorMessage

Enter a valid U.S. ZIP code using the format 12345 or 12345-1234

 pattern

^\d{5}(-\d{4})?$

 class

info.magnolia.ui.form.field.definition.TextFieldDefinition

 label

Zip code

Custom validators

To write your own validator class:

  1. Create a validator class that performs the actual validation. 
  2. Create a validator factory class that extends AbstractFieldValidatorFactory . Implement the createValidator method.
  3. Create a validator definition class that extends ConfiguredFieldValidatorDefinition . In the definition class, set the factory class.

Example: Checking that a username is unique.

  • UniqueUserNameValidator
  • UniqueUserNameValidatorFactory
  • UniqueUserNameValidatorDefinition

Checking for null values

Best practice

Define default values for fields or check for null values. This ensures that you can submit the form. For example, if you define an optional option group field field and don't provide a default value, an error occurs when a user submits the form by mail. The email processor does not check for null value in the template. It is good practice to check for null values of any variables you call.

You can check for null values and provide a default value in a Freemarker script like this:

field: ${field!"value not provided"}