根据文件的下一行插入或更新数据库

Question

I have as a text file:

which contains information relating to the order of books where a single order can contain multiple copies of one or more books.

I want to compute the total amount a customer spent in a single order, thus numCopies * bookPrice for each ISBN in an order. The first order would be (1*15.99) = 15.99. The second (10*11.99 + 20*14.99) = 419.70. And the third again (1*15.99).

I am going through the text file with scanner, adding elements of the text file into the text file as I go along. To compute the order total I am trying to accumulate the cost of each book where one is present on a line, until a line is reached where the orderNum changes. Then insert that total order amount into the database.

Im unsure I can correctly check for when an order total should be released and reset for the next ordernumber and insert this total into the database. Or essentially compute the total as I go along and then update the database once I have read all the order data.

relevant code:

class TestConnect {
    static final String DROP_TABLE_BOOKORDER = "drop table if exists bookorder;";

    static final String CREATE_TABLE_BOOKORDER =
            "create table bookorder (" +
                    "  ordernumber VARCHAR(13) NOT NULL," +
                    "  customername VARCHAR(100)," +
                    "  orderdate DATE NOT NULL," +
                    "  discount NUMERIC(8,2) NOT NULL," +
                    "  totalamount INT NOT NULL," +
                    "  PRIMARY KEY (ordernumber));";

    static final String INSERT_BOOKORDER_DATA = "insert into bookOrder (orderNumber, customerName, orderDate, discount, totalAmount) values (?, ?, ?, ?, ?);";

    createTables();
    loadTables();

    static void createTables() throws SQLException {
        Statement stmt = conn.createStatement();
        stmt.execute(DROP_TABLE_BOOKORDER);
        stmt.execute(CREATE_TABLE_BOOKORDER);

    }

    static void loadTables() throws SQLException, FileNotFoundException, ParseException {
    Scanner lineScanner = new Scanner(new File(orderData));
        String headerLine = lineScanner.nextLine();

        float totalOrderAmount = 0.0f;
        String previousKnownOrderNum = null;

        while (lineScanner.hasNextLine()) {
                String[] retrievedOrderLine = lineScanner.nextLine().split("\t");


                // if order number exists
                if (!Objects.equals(retrievedOrderLine[0], "")) {
                    previousKnownOrderNum = retrievedOrderLine[0];

                    // order number
                    bookOrderStmt.setString(1, retrievedOrderLine[0]);

                    //customer name
                    bookOrderStmt.setString(2, retrievedOrderLine[1]);


                    //order date
                    //handle date format conversion
                    String orderDate = retrievedOrderLine[2];
                    System.out.println("now processing book order date as " + retrievedOrderLine[2]);
                    SimpleDateFormat formattedDate = new SimpleDateFormat("yyyy-MM-dd");
                    java.util.Date date = formattedDate.parse(orderDate);
                    java.sql.Date sqlFormattedDate = new java.sql.Date(date.getTime());
                    bookOrderStmt.setDate(3, sqlFormattedDate);

                    // discount
                    bookOrderStmt.setFloat(4, Float.parseFloat(retrievedOrderLine[3]));


            }

                    // if line contains a book isbn
                    if(!Objects.equals(retrievedOrderLine[4], "")) {

                        // if next line contains an orderNumber (the length of the line = 10), then insert accumulated orderTotal into database
                        if (lineScanner.nextLine().length() == 10) {

                            float thisLinesAmount = Float.parseFloat(retrievedOrderLine[5]) * Float.parseFloat(retrievedOrderLine[6]);

                            totalOrderAmount = totalOrderAmount + thisLinesAmount;
                            bookOrderStmt.setFloat(5, totalOrderAmount);

                            // reset total amount
                            totalOrderAmount = 0.0f;

                            // else continue to accumulate
                        } else {

                            // insert a temp value for totalAmount

                            totalOrderAmount = totalOrderAmount + Float.parseFloat(retrievedOrderLine[5]) * Float.parseFloat(retrievedOrderLine[6]);
                            bookOrderStmt.executeUpdate();
                            bookOrderStmt.close();
                        }
                    }

        }
    }
}

test file:

OrderNum    CustName    OrderDate   Discount    ISBN    NumCopies   BookPrice   ShipmentID  ShipmentDate    ShipCopies
N201700001  John Doe    2017-4-24   1   1234567891  1   15.99   S0000003    2017-4-25   1
N201700002  Jane Doe    2017-3-1    41.97   1234567890  10  11.99   S0000001    2017-3-2    5
                            S0000002    2017-3-15   5
                1234567891  20  14.99   S0000001    2017-3-2    15
                            S0000002    2017-3-15   5
N201700003  John Jones  2017-5-1    0   1234567891  1   15.99

Answer 1

I think it get's much clearer if you do it a bit more object oriented.

Think of this helper class (getters/setters omitted for shortness of answer):

 public class BookOrder {
    public String ordernumber;
    public String customerName;
    public Date orderDate;
    public double discount;
    public float totalamount;
    public BookOrder(String on, String cn, Date od, double disc) {
        ordernumber = on;
        customerName = cn;
        orderDate = od;
        discount = disc;
        totalamount = 0;
    }
    public void addAmount(float amount) {
        totalamount += amount * discount;
    }
 }

Which this in place you can write your loop much easier:

static void loadTables() {
    Scanner lineScanner = new Scanner(new File(orderData));
    // skip headers
    String headerLine = lineScanner.nextLine();

    BookOrder currentOrder = null;
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");

    while (lineScanner.hasNextLine()) {
            String[] retrievedOrderLine = lineScanner.nextLine().split("\t");

            // if order number exists
            if (!Objects.equals(retrievedOrderLine[0], "")) {
                //Ordernumber changed, but not null
                if(currentOrder != null || 
                        !currentOrder.ordernumber.equals(retrievedOrderLine[0])) {
                    //Insert into DB
                    insertBookOrder(currentOrder);
                }
                //Ordernumber changed or null (first order)
                if(currentOrder == null || 
                        !currentOrder.ordernumber.equals(retrievedOrderLine[0])) {  
                    //Start the next order as ordernumber changed
                    currentOrder =new BookOrder(
                            retrievedOrderLine[0], //ordernumber
                            retrievedOrderLine[1], //customer
                            dateFormat.parse(retrievedOrderLine[2]), //date
                            Float.parseFloat(retrievedOrderLine[3]) //discount
                            );
                }
            }
            //Now add to total (discount is taken care of in method)
            currentOrder.addAmount(Float.parseFloat(retrievedOrderLine[5]));                            
        }
        //Afterwards we need to insert last item if it exists
        if(currentOrder != null) {
            //Insert into DB
            insertBookOrder(currentOrder);
        }
    }