Como recuperar o entityManager? (Spring)

Properties props = new Properties();
        props.setProperty("java.naming.factory.initial", "com.sun.enterprise.naming.SerialInitContextFactory");

        props.setProperty("org.omg.CORBA.ORBInitialHost", "localhost");
        props.setProperty("org.omg.CORBA.ORBInitialPort", "3700");
        ctxt = new InitialContext(props);
        em = (EntityManagerRemote) ctxt.lookup("EntityManagerBean");