I need to create an object using the id of the object from a MySQL Database

Question

I am working on an Inventory Management System and I am on the last part which is allowing a user to update an order. This update needs to add or remove an item from an order. I am just working on the add part right now. I have the MySQL Query that I have tested that works in Workbench:

INSERT INTO order_items (item_quantity, fk_item_id, fk_order_id) VALUES (1,  (SELECT item_id FROM items WHERE item_id= 1), (SELECT order_id FROM orders WHERE order_id=2));

In Java, I know need to create an Item object from the ID that I pass in above. Here is the OrderDAO:

public Order addItem(Order order) {
        ItemDAO itemDao = new ItemDAO();
        try (Connection connection = DBUtils.getInstance().getConnection();
                PreparedStatement statement = connection.prepareStatement("INSERT INTO order_items (item_quantity, fk_item_id, fk_order_id) VALUES (?,  (SELECT item_id FROM items WHERE item_id = ?), (SELECT order_id FROM orders WHERE order_id = ?));");) {
            statement.setInt(1, order.getItemQuantity());
            statement.setLong(2, order.getItemId());
            itemDao.read(order.getItemId());
            statement.setLong(3, order.getOrderId());
            statement.executeUpdate();
            System.out.println(order);
            return read(order.getOrderId());
        }  catch (Exception e) {
            LOGGER.debug(e);
            LOGGER.error(e.getMessage());
        }
        return null;
    }

And here is the Controller:

@Override
    public Order update() {
        LOGGER.info("Please enter the id of the order you would like to update");
        Long id = utils.getLong();
//      LOGGER.info("Would you like to add or delete an item from an order");
        LOGGER.info("Please enter the ID of the item you wish to add");
        Long itemId = utils.getLong();
        LOGGER.info("Please enter the quantity of the item to add");
        int quantity = utils.getInt();
        Item item = new Item(itemId);
        System.out.println(item);
        Order order = orderDAO.addItem(new Order(item, quantity, id));
        LOGGER.info("Order Updated\n");
        return order;
    }

I saw something similar here but not quite sure how to adapt it. I know I am just around the corner from the penny dropping, as I thought about using ItemDAO.read(Long id) method I have in the ItemDAO Class, but I don't know how to then set the properties of the Item object using that method.

New to working with the DAO model and JDBC so if there is already an answer for this I couldn't find it so if I get pointed in the right direction I would be more than grateful.

Edit: This is the ItemDAO read() method and the modelFromResults() method:

@Override
    public Item read(Long id) {
        try (Connection connection = DBUtils.getInstance().getConnection();
                PreparedStatement statement = connection.prepareStatement("SELECT * FROM items WHERE item_id = ?");) {
            statement.setLong(1, id);
            try (ResultSet resultSet = statement.executeQuery();) {
                resultSet.next();
                return modelFromResultSet(resultSet);
            }
        } catch (Exception e) {
            LOGGER.debug(e);
            LOGGER.error(e.getMessage());
        }
        return null;

@Override
    public Item modelFromResultSet(ResultSet resultSet) throws SQLException {
        Long itemID = resultSet.getLong("item_id");
        String itemName = resultSet.getString("item_name");
        double itemCost = resultSet.getDouble("item_cost");
        return new Item(itemID, itemName, itemCost);
    }

Answer 1

The Solution:

OrderDAO:

public Order orderItemsFromResultSet(ResultSet rs) throws SQLException {
        Long orderId = rs.getLong("order_items_id");
        Long itemId = rs.getLong("item_id");
        String itemName = rs.getString("item_name");
        double itemCost = rs.getDouble("item_cost");
        Item item = new Item(itemId, itemName, itemCost);
        Order order = new Order(item, orderId);
        return order;
    }
    @Override
    public Order read(Long id) {
        try (Connection connection = DBUtils.getInstance().getConnection();
                PreparedStatement statement = connection.prepareStatement("SELECT * FROM order_items LEFT OUTER JOIN items ON items.item_id = order_items.fk_item_id WHERE fk_order_id = ?;");) {
            statement.setLong(1, id);
            try (ResultSet resultSet = statement.executeQuery();) {
                resultSet.next();
                return orderItemsFromResultSet(resultSet);
            }
        } catch (Exception e) {
            LOGGER.debug(e);
            LOGGER.error(e.getMessage());
        }
        return null;
    }
public Order addItem(Order order) {
        
        try (Connection connection = DBUtils.getInstance().getConnection();
                PreparedStatement statement = connection.prepareStatement("INSERT INTO order_items (item_quantity, fk_item_id, fk_order_id) VALUES (?,  (SELECT item_id FROM items WHERE item_id = ?), (SELECT order_id FROM orders WHERE order_id = ?));");) {
            statement.setInt(1, order.getItemQuantity());
            statement.setLong(2, order.getItemId());
            statement.setLong(3, order.getOrderId());
            statement.executeUpdate();
            return read(order.getOrderId());
        }  catch (Exception e) {
            LOGGER.debug(e);
            LOGGER.error(e.getMessage());
        }
        return null;
    }
public Order removeItem(Order order) {
        try (Connection connection = DBUtils.getInstance().getConnection();
                PreparedStatement statementOne = connection.prepareStatement("UPDATE order_items SET item_quantity = item_quantity - 1 WHERE item_quantity >= 0 && fk_item_id = ? && fk_order_id = ?");
                PreparedStatement statementTwo = connection.prepareStatement("DELETE FROM order_items WHERE item_quantity = 0");) {
            statementOne.setLong(1, order.getItemId());
            statementOne.setLong(2, order.getOrderId());
            statementOne.executeUpdate();
            statementTwo.executeUpdate();
        }  catch (Exception e) {
            LOGGER.debug(e);
            LOGGER.error(e.getMessage());
        }
        return null;
    }

OrderController:

@Override
    public Order update() {
        LOGGER.info("Please enter the id of the order you would like to update");
        Long id = utils.getLong();
        LOGGER.info("Would you like to add or delete an item from an order");
        String addOrDelete = utils.getString();
        addOrDelete = addOrDelete.toLowerCase();
        if (addOrDelete.equals("add")) {
            LOGGER.info("Please enter the ID of the item you wish to add");
            Long itemId = utils.getLong();
            LOGGER.info("Please enter the quantity of the item to add");
            int quantity = utils.getInt();
            Item item = new Item(itemId);
            ItemDAO itemDao = new ItemDAO();
            item = itemDao.read(item.getItemID());
            Order order = orderDAO.addItem(new Order(item.getItemID(), quantity, id));
            LOGGER.info("Order Updated\n");
            return order;
        } 
        else if (addOrDelete.equals("delete")) {
            LOGGER.info("Please enter the id of the item you wish to remove");
            Long itemId = utils.getLong();
            Order order = new Order();
            order.setOrderId(id);
            order.setItemId(itemId);
            orderDAO.removeItem(order);
            LOGGER.info("Order Updated\n");
            return order;
        }
        return null;
    }

This has both full functionality for adding an item and removing an item, deleting any orders where the item quantity hits 0.