Constraint violated, transaction rolled back

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>

That way you can directly access your violations.