public List<Myshopee_ProductTO> getProductList() {
    EntityManager em = null;
    try {
      EntityManagerFactory emf = Persistence.createEntityManagerFactory("Group4");
      List<Myshopee_Product> list = new ArrayList<Myshopee_Product>();
      List<Myshopee_ProductTO> list1 = new ArrayList<Myshopee_ProductTO>();
      em = emf.createEntityManager();

      Query query = em.createQuery("select p from Myshopee_Product p");
      list = query.getResultList();
      for (int index = 0; index < list.size(); index++) {
        Myshopee_Product product = new Myshopee_Product();
        Myshopee_ProductTO productTO = new Myshopee_ProductTO();
        product = (Myshopee_Product) list.get(index);
        productTO.setProductId(product.getProductId());
        productTO.setProductName(product.getProductName());
        productTO.setAssociatedPoints(productTO.getAssociatedPoints());
        productTO.setQtyInStock(product.getQtyInStock());
        productTO.setCategory(product.getCategory());
        productTO.setPricePerUnit(product.getPricePerUnit());
        list1.add(productTO);
      }
      return list1;

    } finally {
      if (em != null) em.close();
    }
  }
  public void updateStock(List<Myshopee_TransactionTO> transactionList)
      throws NoProductException, Exception {
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("Group4");
    EntityManager em = null;

    try {
      em = emf.createEntityManager();
      em.getTransaction().begin();

      if (transactionList.isEmpty()) {
        throw new NoProductException();
      }

      for (Myshopee_TransactionTO transactionTO : transactionList) {
        int productId = transactionTO.getProductId();
        Myshopee_Product product = em.find(Myshopee_Product.class, productId);
        if (product != null) {
          product.setQtyInStock(product.getQtyInStock() - transactionTO.getQuantityPurchased());
        }
      }

      em.getTransaction().commit();
    } catch (NoProductException e) {
      ErrorLogger.logError(this.getClass().getName(), "updateStock", e.getMessage());
      throw e;
    } catch (Exception e) {
      ErrorLogger.logError(this.getClass().getName(), "updateStock", e.getMessage());
      throw e;
    }
  }
  public Myshopee_ProductTO getProductFromId(int productId) throws Exception {
    EntityManager em = null;
    try {
      EntityManagerFactory emf = Persistence.createEntityManagerFactory("Group4");

      em = emf.createEntityManager();
      Myshopee_Product product = new Myshopee_Product();
      Myshopee_ProductTO productTO = new Myshopee_ProductTO();
      product = em.find(Myshopee_Product.class, productId);
      if (product != null) {
        productTO.setProductId(product.getProductId());
        productTO.setProductName(product.getProductName());
        productTO.setAssociatedPoints(productTO.getAssociatedPoints());
        productTO.setQtyInStock(product.getQtyInStock());
        productTO.setCategory(product.getCategory());
        productTO.setPricePerUnit(product.getPricePerUnit());
        return productTO;
      } else {
        throw new ProductNotFoundException();
      }
    } catch (Exception e) {
      ErrorLogger.logError(this.getClass().getName(), "getProductFromId", e.getMessage());
      throw e;
    } finally {
      if (em != null) em.close();
    }
  }
  public List<Myshopee_ProductTO> getProductsFromCategory(char category)
      throws NoProductInCategoryException, Exception {
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("Group4");
    EntityManager em = null;
    List<Myshopee_ProductTO> productTOList = new ArrayList<Myshopee_ProductTO>();

    try {
      em = emf.createEntityManager();

      Query query = em.createQuery("select p from Myshopee_Product p where p.category = ?1");
      query.setParameter(1, category);
      List<Object> productList = query.getResultList();
      if (productList == null || productList.isEmpty()) {
        throw new NoProductInCategoryException();
      }

      for (Object object : productList) {
        Myshopee_Product product = (Myshopee_Product) object;

        Myshopee_ProductTO productTO = new Myshopee_ProductTO();
        productTO.setProductId(product.getProductId());
        productTO.setProductName(product.getProductName());
        productTO.setAssociatedPoints(product.getAssociated_points());
        productTO.setQtyInStock(product.getQtyInStock());
        productTO.setPricePerUnit(product.getPricePerUnit());
        productTO.setCategory(product.getCategory());

        // adding to the list of productTO
        productTOList.add(productTO);
      }
    } catch (NoProductInCategoryException e) {
      ErrorLogger.logError(this.getClass().getName(), "getProductsFromCategory", e.getMessage());
      throw e;
    } catch (Exception e) {
      ErrorLogger.logError(this.getClass().getName(), "getProductsFromCategory", e.getMessage());
      throw e;
    } finally {
      if (em != null) {
        em.close();
      }
    }

    return productTOList;
  }
  @SuppressWarnings("unchecked")
  public List<Myshopee_ProductTO> getProductFromCategory(char category) throws Exception {
    EntityManager em = null;
    try {
      EntityManagerFactory emf = Persistence.createEntityManagerFactory("Group4");
      List<Myshopee_Product> list = new ArrayList<Myshopee_Product>();
      List<Myshopee_ProductTO> list1 = new ArrayList<Myshopee_ProductTO>();
      em = emf.createEntityManager();

      Query query = em.createQuery("select p from Myshopee_Product p where p.category=?1");
      query.setParameter(1, category);
      list = query.getResultList();
      if (list.size() != 0) {
        for (int index = 0; index < list.size(); index++) {
          Myshopee_Product product = new Myshopee_Product();
          Myshopee_ProductTO productTO = new Myshopee_ProductTO();
          product = (Myshopee_Product) list.get(index);
          productTO.setProductId(product.getProductId());
          productTO.setProductName(product.getProductName());
          productTO.setAssociatedPoints(productTO.getAssociatedPoints());
          productTO.setQtyInStock(product.getQtyInStock());
          productTO.setCategory(product.getCategory());
          productTO.setPricePerUnit(product.getPricePerUnit());
          list1.add(productTO);
        }
        return list1;
      } else {
        throw new NoProductInCategoryException();
      }

    } catch (NoProductInCategoryException e) {
      ErrorLogger.logError(this.getClass().getName(), "getProductFromCategory", e.getMessage());
      throw e;
    } catch (Exception e) {
      ErrorLogger.logError(this.getClass().getName(), "getProductFromCategory", e.getMessage());
      throw e;
    } finally {
      if (em != null) em.close();
    }
  }