When using JPA with hibernate, in Entity Beans we can define data validations using annotations as follows,

import org.hibernate.validator.Email;
import org.hibernate.validator.Length;

@Length(min=2, max=25, message="not a valid mail")
@Email

Atleast when user selected Hibernate, it will be good if Entity Beans generated can generate some default validations
for data variables. It will help users in quickly updating these as required and have very good code.

Similarly in JSF pages we can provide validations for each of the variables as follows,

<h:inputText value = "#{UserBean.userName}" id = "userNameTextField" required="true">
    <f:validateLength minimum = "10" maximum = "15"/>
</h:inputText>

Likewise when generating JSF pages from Entity beans, if it can refer back to Entity beans and generate validations that
will be helpful. If not available, if it can generate some default values for validations, that's also very helpful.

Change Suggested : During the code generation process, check with user if default data validations need to generated.