public class WriteTest extends HttpServlet
{
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    {
        /*try
        { 
            User user = new User("Hans", "Maulwurf", "hans.maulwurf@test.de");
           
            InitialContext ctx = new InitialContext();
            UserFacadeBean bean = (UserFacadeBean) ctx.lookup("ejb/UserFacadeBeanService");
            bean.persist(user);
        }
        catch (NamingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }*/
       
        EntityManager em = JpaUtil.getEntityManagerFactory().createEntityManager();
        //em.getTransaction().begin();
       
        System.out.println("Begin transfer");
       
        User user = new User("Hans", "Maulwurf", "hans.maulwurf@test.de");
        Adress adress = new Adress("Deppenstraße 3","Deppingen");
        //user.setAddress(adress);
       
        System.out.println("Save User 'Hans Maulwurf'");
       
        em.persist(user);
        //em.persist(adress);
        //em.getTransaction().commit();
        em.close();
       
        System.out.println("Everything went better than expected!");
    }
}

public class JpaUtil
{
    private static final EntityManagerFactory emf;

    static
    {
        try
        {
            System.out.println("Initialize EntityManagerFactory...");
            emf = Persistence.createEntityManagerFactory("testPU");
        }
        catch (Throwable ex)
        {
            System.err.println("Initial EntityManagerFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static EntityManagerFactory getEntityManagerFactory()
    {
        return emf;
    }
}

@Entity
@Table(name = "T_UserJpa")
public class User implements Serializable
{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    @Embedded
    @AttributeOverrides(
    {
        @AttributeOverride(name = "street", column =
        @Column(name = "user_street")),
        @AttributeOverride(name = "city", column =
        @Column(name = "user_city", length = 50))
    })
    private Adress adress;
    private String firstname;
    private String lastname;
    private String email;

    public User()
    {
    }

    public User(String firstname, String lastname, String email)
    {
        this.firstname = firstname;
        this.lastname = lastname;
        this.email = email;
    }

    public Long getId()
    {
        return id;
    }

    public void setId(Long id)
    {
        this.id = id;
    }

    public Adress getAddress()
    {
        return adress;
    }

    public void setAddress(Adress adress)
    {
        this.adress = adress;
    }

    public String getFirstname()
    {
        return firstname;
    }

    public void setFirstname(String firstname)
    {
        this.firstname = firstname;
    }

    public String getLastname()
    {
        return lastname;
    }

    public void setLastname(String lastname)
    {
        this.lastname = lastname;
    }

    public String getEmail()
    {
        return email;
    }

    public void setEmail(String email)
    {
        this.email = email;
    }

    @Override
    public boolean equals(Object obj)
    {
        if (this == obj)
        {
            return true;
        }
        if (!(obj instanceof User))
        {
            return false;
        }
        final User user = (User) obj;
        return !(email != null ? !email.equals(user.email) : user.email != null);
    }

    @Override
    public int hashCode()
    {
        return 29 * (email != null ? email.hashCode() : 0);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence">
  <persistence-unit name="testPU" transaction-type="JTA">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <jta-data-source>jdbc/testdb</jta-data-source>
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/>
      <property name="hibernate.show_sql" value="true"/>
      <property name="hibernate.transaction.factory_class" value="org.hibernate.transaction.JTATransactionFactory"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
      <property name="hibernate.connection.autocommit" value="true"/>
    </properties>
  </persistence-unit>
</persistence>