WEB-INF/classes/META-INF/persistence.xml

<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">
  <!--
     - Specifies the example's persistence unit.
    -->
  <persistence-unit name="example">
    <class>example.Student</class>
    <class>example.Course</class>
    <class>example.Grade</class>

    <exclude-unlisted-classes/>
  </persistence-unit>
</persistence>