Package org.springframework.validation

Interface Validator

All Known Subinterfaces:

SmartValidator

All Known Implementing Classes:

CustomValidatorBean, LocalValidatorFactoryBean, OptionalValidatorFactoryBean, SpringValidatorAdapter

public interface Validator

A validator for application-specific objects.

This interface is totally divorced from any infrastructure or context; that is to say it is not coupled to validating only objects in the web tier, the data-access tier, or the whatever-tier. As such it is amenable to being used in any layer of an application, and supports the encapsulation of validation logic as a first-class citizen in its own right.

Implementations can be created via the static factory methods forInstanceOf(Class, BiConsumer) or forType(Class, BiConsumer). Below is a simple but complete Validator that validates that the various String properties of a UserLogin instance are not empty (they are not null and do not consist wholly of whitespace), and that any password that is present is at least 'MINIMUM_PASSWORD_LENGTH' characters in length.

Validator userLoginValidator = Validator.forInstance(UserLogin.class, (login, errors) -> {
   ValidationUtils.rejectIfEmptyOrWhitespace(errors, "userName", "field.required");
   ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "field.required");
   if (login.getPassword() != null
         && login.getPassword().trim().length() < MINIMUM_PASSWORD_LENGTH) {
      errors.rejectValue("password", "field.min.length",
            new Object[]{Integer.valueOf(MINIMUM_PASSWORD_LENGTH)},
            "The password must be at least [" + MINIMUM_PASSWORD_LENGTH + "] characters in length.");
   }
 });

See also the Spring reference manual for a fuller discussion of the Validator interface and its role in an enterprise application.

Author:

Rod Johnson, Toshiaki Maki, Arjen Poutsma

See Also:

• SmartValidator
• Errors
• ValidationUtils

Method Summary

Modifier and Type	Method	Description
static <T> Validator	forInstanceOf(Class<T> targetClass, BiConsumer<T,Errors> delegate)	Return a Validator that checks whether the target object is an instance of targetClass, applying the given delegate to populate Errors if it is.
static <T> Validator	forType(Class<T> targetClass, BiConsumer<T,Errors> delegate)	Return a Validator that checks whether the target object's class is identical to targetClass, applying the given delegate to populate Errors if it is.
boolean	supports(Class<?> clazz)	Can this Validator validate instances of the supplied clazz?
void	validate(Object target, Errors errors)	Validate the supplied target object, which must be of a Class for which the supports(Class) method typically has (or would) return true.

Method Details

supports

boolean supports(Class<?> clazz)

Can this Validator validate instances of the supplied clazz?

This method is typically implemented like so:

return Foo.class.isAssignableFrom(clazz);

(Where Foo is the class (or superclass) of the actual object instance that is to be validated.)

Parameters:

clazz - the Class that this Validator is being asked if it can validate

Returns:

true if this Validator can indeed validate instances of the supplied clazz

validate

void validate(Object target,
 Errors errors)

Validate the supplied target object, which must be of a Class for which the supports(Class) method typically has (or would) return true.

The supplied errors instance can be used to report any resulting validation errors.

Parameters:

target - the object that is to be validated

errors - contextual state about the validation process

See Also:

• ValidationUtils

forInstanceOf

static <T> Validator forInstanceOf(Class<T> targetClass,
 BiConsumer<T,Errors> delegate)

Return a Validator that checks whether the target object is an instance of targetClass, applying the given delegate to populate Errors if it is.

For instance:

Validator passwordEqualsValidator = Validator.forInstanceOf(PasswordResetForm.class, (form, errors) -> {
   if (!Objects.equals(form.getPassword(), form.getConfirmPassword())) {
           errors.rejectValue("confirmPassword",
                 "PasswordEqualsValidator.passwordResetForm.password",
                 "password and confirm password must be same.");
           }
         });

Type Parameters:

T - the target object type

Parameters:

targetClass - the class supported by the returned validator

delegate - function invoked with the target object, if it is an instance of type T

Returns:

the created Validator

Since:

6.1

forType

static <T> Validator forType(Class<T> targetClass,
 BiConsumer<T,Errors> delegate)

Return a Validator that checks whether the target object's class is identical to targetClass, applying the given delegate to populate Errors if it is.

For instance:

Validator passwordEqualsValidator = Validator.forType(PasswordResetForm.class, (form, errors) -> {
   if (!Objects.equals(form.getPassword(), form.getConfirmPassword())) {
           errors.rejectValue("confirmPassword",
                 "PasswordEqualsValidator.passwordResetForm.password",
                 "password and confirm password must be same.");
           }
         });

Type Parameters:

T - the target object type

Parameters:

targetClass - the exact class supported by the returned validator (no subclasses)

delegate - function invoked with the target object, if it is an instance of type T

Returns:

the created Validator

Since:

6.1