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Issue with dropdown menu in the jsp page(cannot import the choice in the db)

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So I want to fix an issue with the jsp page. As you may see this form is for registering a new product into database. You add some stuff like ID of product, some category of a product(if it is electronic part, etc), and some other stuff. My problem is selecting categories from the dropdown menu.. To be more specific, I add a product in the form and when I create a new category I don't have any problems, but when I add a product and use the dropdown menu(when I have an already existed category) the category field in the db is blank. I have added some extra code just in case that the problem is connected with more than the jsp file. I will explain it to you with some examples to be more clear. In the first screenshot I add a product and then I create a category. In the second one I create a product and then I select on of the category I want. The last one is the database with all of the saved products.

index.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@page import="java.sql.*"%>

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <script src="JsBarcode.all.min.js"></script>
    <link rel="icon" type="image/png" href="6077105.png">
    <title>Storage Room</title>
    <style type="text/css">
        body {
            font-family: system-ui, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Oxygen, Ubuntu, Cantarell, Fira Sans, Droid Sans, Helvetica Neue, Segoe UI Emoji, Apple Color Emoji, Noto Color Emoji, sans-serif;
            background-color: #202b38;
            color: white;
            margin: 0; /* Remove default margin to ensure full width */
        }

        .Title {
            font-size: 10px;
        }

        a:link, visited {
            color: white;
        }
        a:hover {
            color: hotpink;
        }

        #navlist a {
            margin-right: 20px; /* Adjust the spacing between navlist items */
        }

        .form-inline {
            display: flex;
            flex-wrap: wrap;
            align-items: center;
        }

        .form-group {
            margin-right: 20px;
            margin-bottom: 10px;
        }

        .form-group label {
            margin-right: 5px;
        }

        .form-group input {
            width: 150px; /* Adjust the input width as needed */
        }

        .btn {
            margin-top: 10px;
        }
    </style>
</head>
<body>
    <div class="Title"><h1>Προσθήκη Προιόντος</h1></div>
    <div id="navlist" class="navlist">
        <a href='homepage.html'>Αρχίκη Σελίδα</a>
    </div>
    <br>
    <div class="products">
        <form name="products" action="SaveServlet" method="post" onsubmit="addNewCategory()" class="form-inline">
            <div class="form-group">
                <label for="ID">ID προιόντος:</label>
                <input type="number" name="prod_barid" id="prod_barid" required>
            </div>
             <div class="form-group">
                <label for="Category">Κατηγορία:</label>
                <select name="category" id="prod_category" onchange="checkNewCategory(this)">
                    <option value="">Δεν υπάρχει κατηγορία...</option>
                    <% 
                        String dbDriver = "org.mariadb.jdbc.Driver"; 
                        String dbURL = "jdbc:mariadb://localhost:3306/BARCODEPROD";
                        String dbUser = "adminB"; 
                        String dbPass = "passwordAdmin";
                        Connection con = null;

                        try {
                            Class.forName(dbDriver);
                            con = DriverManager.getConnection(dbURL, dbUser, dbPass);
                            String query = "SELECT DISTINCT prod_category FROM products";
                            Statement st = con.createStatement();
                            ResultSet rs = st.executeQuery(query);
                            while (rs.next()) {
                                String category = rs.getString("prod_category");
                    %>
                    <option value="<%= category %>"><%= category %></option>
                    <%
                            }
                            rs.close();
                            st.close();
                            con.close();
                        } catch(Exception ex) {
                            ex.printStackTrace();
                        }
                    %>
                </select>
            </div>
            <div class="form-group">
                <label for="Product">Προιόν:</label>
                <input type="text" name="product_name" id="prod_name" required>
            </div>
            <div class="form-group">
                <label for="pcs">Ποσότητα:</label>
                <input type="number" name="pcs" id="pcs" required>
            </div>
            <div class="form-group">
                <label for="price">Τιμή:</label>
                <input type="number" name="price" id="price" step="any">
            </div>
            <div class="form-group">
                <label for="Description">Παρατηρήσεις:</label>
                <input type="text" name="prod_description" id="prod_description">
            </div>
            <div class="form-group">
                <label for="newCategory">Νέα κατηγορία:</label>
                <input type="text" name="prod_category" id="prod_category">
            </div>
            <button id="submit_btn" type="submit">Προσθήκη</button>
            <svg id="barcode"></svg>
            <button id="clear_all_btn" type="reset">Εκαθάριση στοιχείων</button>
        </form>
    </div>
</body>
</html>

SaveServlet.java


import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.SQLIntegrityConstraintViolationException;
import java.util.Calendar;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.http.HttpSession;

@WebServlet("/SaveServlet")
public class SaveServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int status = 0;
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String name = request.getParameter("product_name");
        String baridParam = request.getParameter("prod_barid");
        long barid = Long.parseLong(baridParam);
        String desc = request.getParameter("prod_description");
        String pcsParam = request.getParameter("pcs");
        int pcs = Integer.parseInt(pcsParam);
        String priceParam = request.getParameter("price");
        double price = Double.parseDouble(priceParam);
        String category = request.getParameter("prod_category");
        String newCategory = request.getParameter("new_prod_category");

        // If a new category is provided, use it; otherwise, use the selected category
        String finalCategory = (newCategory != null && !newCategory.isEmpty()) ? newCategory : category;


        // Validate and handle the Date field
        Date date = getCurrentDate();

        // Check if the item with the same name or barcode exists in the database
        boolean itemExists = checkItemExists(name, baridParam);

        if (itemExists) {
            out.println("<!DOCTYPE html>");
            out.println("<html><head>");
            out.println("<meta charset=\"UTF-8\">");
            out.println("<link rel=\"stylesheet\" href=\"https://cdn.jsdelivr.net/npm/water.css@2/out/water.min.css\">\n");
            out.println("</head>");
            out.println("<body>");
            out.println("<p>Item with the same name or barcode already exists. Retry with a different name or barcode.</p>");
            out.println("</body>");
            out.println("</html>");
        } else {
            Products products = new Products();
            products.setProd_name(name);
            products.setProd_barid(barid); //products.setProd_barid(baridParam);
            products.setProd_description(desc);
            products.setProd_added_date(date);
            products.setPcs(pcs);
            products.setPrice(price);
            products.setProd_category(finalCategory);
            HttpSession session = request.getSession();

            try {
                Connection con = Main.initializeDB();
                PreparedStatement st = con.prepareStatement("INSERT INTO products (prod_barid, prod_category, prod_name, pcs, price, prod_description, prod_added_date) VALUES (?, ?, ?, ?, ?, ?, ?)");

                st.setString(1, String.valueOf(products.getProd_barid()));
                st.setString(2, products.getProd_category());
                st.setString(3, products.getProd_name());
                st.setInt(4, products.getPcs());
                st.setDouble(5, products.getPrice());
                st.setString(6, products.getProd_description());
                st.setDate(7, products.getProd_added_date());

                status = st.executeUpdate();
                st.close();
                con.close();
                if (status > 0) {
                    response.sendRedirect("index.jsp");
                } else {
                    out.println("UNABLE TO ADD IT... RETRY AGAIN PLEASE");
                }
            } catch (SQLIntegrityConstraintViolationException e) {
                // Catch the exception when trying to insert a duplicate item
                out.println("<!DOCTYPE html>");
                out.println("<html><head>");
                out.println("<meta charset=\"UTF-8\">");
                out.println("<link rel=\"stylesheet\" href=\"https://cdn.jsdelivr.net/npm/water.css@2/out/water.min.css\">\n");
                out.println("</head>");
                out.println("<body>");
                out.println("<p>Item with the same name or barcode already exists. Retry with a different name or barcode.</p>");
                out.println("</body>");
                out.println("</html>");
            } catch (ClassNotFoundException | SQLException ex) {
                ex.printStackTrace();
            }
        }
        out.close();
    }

    // Check if an item with the same name or barcode exists in the database
    private boolean checkItemExists(String name, String barcode) {
        try {
            Connection con = Main.initializeDB();
            PreparedStatement st = con.prepareStatement("SELECT COUNT(*) FROM products WHERE prod_name = ? OR prod_barid = ?");
            st.setString(1, name);
            st.setString(2, barcode);
            ResultSet rs = st.executeQuery();
            rs.next();
            int count = rs.getInt(1);
            rs.close();
            st.close();
            con.close();
            return count > 0;
        } catch (ClassNotFoundException | SQLException ex) {
            ex.printStackTrace();
        }
        return false;
    }

    private Date getCurrentDate() {
        Calendar calendar = Calendar.getInstance();
        java.util.Date utilDate = calendar.getTime();
        return new Date(utilDate.getTime());
    }
}

db.sql

CREATE USER 'adminB'@'localhost' IDENTIFIED BY 'passwordAdmin';
GRANT ALL ON BARCODEPROD.* TO 'adminB'@'localhost';
FLUSH PRIVILEGES;

CREATE DATABASE IF NOT EXISTS BARCODEPROD;
USE BARCODEPROD;

CREATE TABLE IF NOT EXISTS users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(255),
    password VARCHAR(255),
    role VARCHAR(20) NOT NULL DEFAULT 'non-admin'
);
    
CREATE TABLE IF NOT EXISTS products ( 
    prod_barid BIGINT NOT NULL PRIMARY KEY,
    prod_name varchar(255) NOT NULL,
    prod_description varchar(255),
    prod_added_date date NOT NULL,
    prod_category varchar(255) NOT NULL,
    pcs int NOT NULL,
    price double NOT NULL,
    totalprc double NOT NULL DOUBLE GENERATED ALWAYS AS (pcs * price) STORED
);

CREATE TABLE IF NOT EXISTS suppliers (
    sup_id int AUTO_INCREMENT PRIMARY KEY,
    sup_name VARCHAR(255),
    sup_surname VARCHAR(255),
    sup_product VARCHAR(255),
    sup_phone int(10),
    sup_address VARCHAR(255),
    sup_website VARCHAR(255)    
);

INSERT INTO users(username,password,role) VALUES('admin','admin123x','admin');
INSERT INTO users(username,password,role) VALUES('moderator','1234','non-admin');

Main.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class Main{
    protected static Connection initializeDB() throws SQLException, ClassNotFoundException {
        String dbDriver = "org.mariadb.jdbc.Driver"; 
        String dbURL = "jdbc:mariadb://localhost:3306/BARCODEPROD";
        String dbUser = "adminB"; 
        String dbPass = "passwordAdmin";
        Connection con = null;
        try { //in case of an mariadb issue..
            Class.forName(dbDriver);
            con = DriverManager.getConnection(dbURL, dbUser, dbPass); //Connection con = DriverManager.getConnection(dbURL + dbName, dbUsername, dbPassword);
        } catch(ClassNotFoundException | SQLException ex) {
            ex.printStackTrace();
        }
        return con;
    }
}

Adding product and adding a category

Adding product and add an already existed category

Database

java html sql forms jsp
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