Question

  public static List<Transaction1> debitSourceAccBalance (Integer youraccinput, Integer toaccinput, String recname, Double amtsender) {
    EntityManager em = emf.createEntityManager();
    em.getTransaction().begin();
    Query q = em.createQuery("SELECT t from Transaction1 t where t.fromAccNo =:youraccinput AND t.toAccNo =:toaccinput AND t.name =:recname AND t.amount >=:amtsender");
    q.setParameter("youraccinput", youraccinput);
    q.setParameter("toaccinput", toaccinput);
    q.setParameter("recname", recname);
    q.setParameter("amtsender", amtsender);
    Double currbal = (Double)q.getSingleResult();

    amtsender = currbal - amtsender;
    Query u = em.createQuery("UPDATE Transaction1 t SET t.amount =:amtsender WHERE t.fromAccNo =:youraccinput AND t.toAccNo =:toaccinput");
    u.setParameter("youraccinput", youraccinput);
    u.setParameter("toaccinput", toaccinput);
    u.setParameter("amtsender", amtsender);

    u.executeUpdate();
    return q.getResultList();

Servlet:

              Integer youraccinput = Integer.parseInt(request.getParameter("fromAccNo"));
              Integer toaccinput = Integer.parseInt(request.getParameter("toAccNo"));
              String recname = request.getParameter("name");
              Double amtsender = Double.parseDouble(request.getParameter("amount"));


        List<Transaction1> results = Transaction1.debitSourceAccBalance(youraccinput, toaccinput, recname, amtsender);
                       results.listIterator();
                       request.getRequestDispatcher("ListSingleTransaction").forward(request, response);

why am i getting this error message?? please help to fix!!

“Entities.Transaction1 cannot be cast
to java.lang.Double”

Answer 1

The cast error is at

Double currbal = (Double)q.getSingleResult();

You don’t even know why you’re casting it?

As a quick fix to help you get pass this one, how to fix this is very simple. Just change it to:

Transaction1 transaction = (Transaction1) q.getSingleResult();
Double currbal = transaction.getCurrentBalance();  // method name assumed

Your JPA query is returning an entity object, not a single primitive value, so you can’t cast it to double because your query did not select a double – it selected a Transaction1 object, hence you need to cast the single result from the query into whatever you selected back.

Read up more on JPA.