@PersistenceUnit(unitName="myPetStorePU")
private EntityManagerFactory emf;

EntityManager em = emf.createEntityManager();

EntityManagerFactory emf = javax.persistence.Persistence.createEntityManagerFactory("myPetStorePU");
    EntityManager em = emf.createEntityManager();

<persistence-unit name="myPetStorePU">
    <description>Petstore Persistence Unit</description>
    <provider>oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider</provider>

  <class>com.sun.javaee.blueprints.petstore.model.Tag</class>
  <class>com.sun.javaee.blueprints.petstore.model.SellerContactInfo</class>
  <class>com.sun.javaee.blueprints.petstore.model.Product</class>
  <class>com.sun.javaee.blueprints.petstore.model.Item</class>
  <class>com.sun.javaee.blueprints.petstore.model.Category</class>
  <class>com.sun.javaee.blueprints.petstore.model.Address</class>
  <class>com.sun.javaee.blueprints.petstore.model.ZipLocation</class>
    <properties>
        <property name="toplink.jdbc.driver" value="oracle.jdbc.driver.OracleDriver"/>
        <property name="toplink.jdbc.url" value="jdbc:oracle:thin:@#############"/>
        <property name="toplink.jdbc.user" value="####"/>
        <property name="toplink.jdbc.password" value="#####"/>
        <property name="toplink.logging.level" value="INFO"/>
    </properties>

</persistence-unit>

<listener>
    <listener-class>com.sun.javaee.blueprints.petstore.model.CatalogFacade</listener-class>
</listener>

<%
CatalogFacade cf = (CatalogFacade)config.getServletContext().getAttribute("CatalogFacade");
List<Tag> tags=cf.getTagsInChunk(0, 12);
%>


public List<Tag> getTagsInChunk(int start, int chunkSize) {
//The next line is required since the @PersistenceUnit annotation at the top of this class does not work
    EntityManagerFactory emf = javax.persistence.Persistence.createEntityManagerFactory("myPetStorePU");
    EntityManager em = emf.createEntityManager();
    System.out.println("Entity manager " + emf);
    Query query = em.createQuery("SELECT t FROM Tag t ORDER BY t.refCount DESC, t.tag");
    List<Tag> tags = query.setFirstResult(start).setMaxResults(chunkSize).getResultList();
    em.close();
    return tags;
}