Error catching mysql statement in java - mysql

Question

Hello so i'm trying to code my own type of error catching on a sql statement. On my method add order i want to add some way of stopping someone from selling a product which has no stock. My code below does not yet do that. I can add orders and update the stock amount but i haven't figured out a way of adding an if statement that works.
#FXML
public void AddOrder(ActionEvent event) {
String orderID = orderBox.getText();
String customerID = customerBox.getText();
String productID = productBox.getText();
String amount = amountBox.getText();
// String cost = costBox.getText();
String date = dateBox.getText();
PreparedStatement sample;
dc = new Database();
try {
c = dc.Connect();
sample = c.prepareStatement("Select stockAmount from inventory WHERE productID = ?");
ResultSet rs = sample.executeQuery();
while (rs.next()) {
Integer amount2 = rs.getInt("Amount");
if (amount2 <= 0) {
System.out.println("No stock exists");
} else {
query = c.prepareStatement(
"INSERT INTO ordertable (orderID,customerID,productID,Amount,Date)VALUES(?,?,?,?,?)");
update = c.prepareStatement("UPDATE inventory set stockAmount = stockAmount-? WHERE productID =?");
update.setString(1, amount);
update.setString(2, productID);
update.execute();
query.setString(1, orderID);
query.setString(2, customerID);
query.setString(3, productID);
query.setString(4, amount);
// query.setString(5, cost);
query.setString(5, date);
query.executeUpdate();
// update.executeUpdate();
Alert confirmation = new Alert(Alert.AlertType.CONFIRMATION, "Saved");
// closeConfirmation.showMessageDialog(this, "Saved");
confirmation.show();
}
}
} catch (Exception e) {
e.printStackTrace();
}
orderBox.clear();
customerBox.clear();
productBox.clear();
amountBox.clear();
dateBox.clear();
loadDataFromDatabase(event);
}
Below is the error i'm getting
java.sql.SQLException: No value specified for parameter 1
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:964)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:897)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:886)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
at

Answer 1

If you are just having trouble because of that exception, check these lines:
sample = c.prepareStatement("Select stockAmount from inventory WHERE productID = ?");
ResultSet rs = sample.executeQuery();
The query is defined to accept a parameter for productID, but you haven't given it a value prior to executing the statement. You'll need to change the query so that it doesn't require a parameter or assign a value to the parameter, like this:
sample = c.prepareStatement("Select stockAmount from inventory WHERE productID = ?");
sample.setString(1, productID);
ResultSet rs = sample.executeQuery();