Package org.apache.tapestry5

Interface Validator<C,T>

All Known Implementing Classes:

AbstractValidator, Checked, Email, Max, MaxLength, Min, MinLength, None, Regexp, Required, Unchecked

public interface Validator<C,T>

Used by a Field to enforce a constraint related to a form submission. Validators themselves are stateless singletons. Validators are usually encapsulated inside a FieldValidator.

See Also:

FieldValidationSupport, FieldValidatorDefaultSource

Method Summary

Modifier and Type	Method	Description
java.lang.Class<C>	getConstraintType()	Returns the type of constraint value used with this validator.
java.lang.String	getMessageKey()	Returns the message key, within the validation messages, normally used by this validator.
java.lang.Class<T>	getValueType()	Returns the value type associated with this validator.
boolean	isRequired()	Returns true if the validator should be invoked for null or blank (empty string) values.
void	render(Field field, C constraintValue, MessageFormatter formatter, MarkupWriter writer, FormSupport formSupport)	Hook used by components to allow the validator to contribute additional attributes or (more often) client-side JavaScript (via the FormSupport.addValidation(Field, String, String, Object)).
void	validate(Field field, C constraintValue, MessageFormatter formatter, T value)	Invoked after the client-submitted value has been translated to check that the value conforms to expectations (often, in terms of minimum or maximum value).

Method Detail

getConstraintType

java.lang.Class<C> getConstraintType()

Returns the type of constraint value used with this validator. Constraint values are used to parameterize a validator, for example a "maxLength" validator will have a constraint value of type int (the maximum length allowed). For constraints that do not have a constraint value, this method returns null.

getValueType

java.lang.Class<T> getValueType()

Returns the value type associated with this validator. validate(Field, Object, MessageFormatter, Object) will only be invoked when the value is assignable to the validator's value type.

getMessageKey

java.lang.String getMessageKey()

Returns the message key, within the validation messages, normally used by this validator. This is used to provide the MessageFormatter passed to validate(Field, Object, MessageFormatter, Object) (unless overridden).

Returns:

a message key

validate

void validate(Field field,
              C constraintValue,
              MessageFormatter formatter,
              T value)
       throws ValidationException

Invoked after the client-submitted value has been translated to check that the value conforms to expectations (often, in terms of minimum or maximum value). If and only if the value is approved by all Validators is the value applied by the field.

Parameters:

field - the field for which a client submitted value is being validated

constraintValue - the value used to constrain

formatter - Validation messages, in the appropriate locale

value - the translated value supplied by the user

Throws:

ValidationException - if the value violates the constraint

isRequired

boolean isRequired()

Returns true if the validator should be invoked for null or blank (empty string) values. This is generally false, but is true for validators that enforce that a non-blank value is required. This is the basis of the Field.isRequired() property.

render

void render(Field field,
            C constraintValue,
            MessageFormatter formatter,
            MarkupWriter writer,
            FormSupport formSupport)

Hook used by components to allow the validator to contribute additional attributes or (more often) client-side JavaScript (via the FormSupport.addValidation(Field, String, String, Object)).

Parameters:

field - the field which is currently being rendered

constraintValue - the value used to constrain input

formatter - validation message, in the appropriate locale

writer - markup writer, allowing additional attributes to be written into the active element

formSupport - used to add JavaScript