| 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 first-class citizens in their own right.
Find below a simple but complete Validator
implementation, which validates that the various
String properties of a UserLogin instance are not empty
(that is 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.
public class UserLoginValidator implements Validator {
private static final int MINIMUM_PASSWORD_LENGTH = 6;
public boolean supports(Class clazz) {
return UserLogin.class.isAssignableFrom(clazz);
}
public void validate(Object target, Errors errors) {
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "userName", "field.required");
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "field.required");
UserLogin login = (UserLogin) target;
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 it's role in a enterprise
application.
author:
Rod Johnson
See Also: Errors
See Also: ValidationUtils |