Quoting from that blog:
When using bean validation on JPA entities within an EJB 3 bean you would actually get an EJBTransactionRolledbackException if there is a constraint violation.
javax.ejb.EJBTransactionRolledbackException: Invalid object at persist time for groups [javax.validation.groups.Default, ]
Caused by: javax.validation.ConstraintViolationException: Invalid object at persist time for groups [javax.validation.groups.Default, ]
This is all nicely according to specification, but not really interesting information. You don't really want to know what happened, you want to know what went wrong.
So I recommend adding the following to your ejb-jar.xml:
<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd"
version="3.0">
<assembly-descriptor>
<application-exception>
<exception-class>javax.validation.ConstraintViolationException</exception-class>
<rollback>true</rollback>
</application-exception>
</assembly-descriptor>
</ejb-jar>