  Bean Validation in Vaadin 7    • submit to reddit  One of
Vaadin 7 key features is its tight JSR 303, also known as Bean
Validation, integration. This article will detail on how to
achieve such a validation.  For starters, let's have a simple
use-case: the user fills in a form. When there's an error, the
user is informed visually about the error. Submitting the form
is only possible when all errors have been corrected. This a
common scenario and we'll implement it with Vaadin.   There are
a couple of prerequisites to address before going further:   1.
First, we'll need a JSR 303 implementation. In this case, we'll
use Hibernate Validator (which is also JSR-303 Reference
Implementation)   2. The next step is to define the underlying
bean. In our case, we'll keep it simple (and stupid): a Person
and its associated attributes. The first name and the last name
must not be null while the email, when it exists, has to respect
an email pattern.     import java.util.Date;     import
javax.validation.constraints.Not