com.mysql.jdbc.des exceptions.jdbc4.MySQLIntegrityConstraintViolationexception: la Colonne "hourId' ne peut pas être null

Mon projet est la faculté de répartition. lorsque j'essaie d'insérer des données, il montre l'exception suivante.

"com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: 
Column 'hourId' cannot be null"

Quelqu'un peut m'aider comment faire pour surmonter ce problème?
Veuillez fournir un exemple de code pour éviter cette exception.

Mon codage est

<%
    Connection con = null;
    String StaffName = request.getParameter("StaffName");
   //String subcode = request.getParameter("subcode");
    String hourId = request.getParameter("hourId");
    String daysId = request.getParameter("daysId");
    String date = request.getParameter("date");


  //String queryText = "insert into tblstaffallocation (StaffName, subcode,hourId, daysId, date) values('"+StaffName+"','"+subcode+"','+hourId+','+daysId+','+date+')";

    try {
          Class.forName("com.mysql.jdbc.Driver");
          con = DriverManager.getConnection("jdbc:mysql://localhost:3306/StaffAllocation","root","success");

       //PreparedStatement stat = con.PrepareStatement();
        String updateString ="INSERT INTO tblstaffallocation (StaffName,hourId,daysId,date) VALUES (?,?,?,?)";

        PreparedStatement preparedStatement = con.prepareStatement(updateString);


        preparedStatement.setString(1, StaffName);
        preparedStatement.setString(2, hourId);
        preparedStatement.setString(3, daysId);
        preparedStatement.setString(4, date);
        preparedStatement.executeUpdate();
        //int rst = stat.executeUpdate("insert into tblstaffallocation ('StaffName','hourId', 'daysId', 'date') values('"+StaffName+"','"+hourId+"','"+daysId+"','"+date+"')");

        %>
        <table cellpadding="4" border="1" cellspacing="4" align="center">
        <th>StaffName</th><th>hourId</th><th>daysId</th><th>date</th>
        <%
        Statement st=con.createStatement();
        ResultSet rs=st.executeQuery("select * from tblstaffallocation");
        while(rs.next()){
            rs.getString(1);
            rs.getString(2);
            rs.getString(3);
            rs.getString(4);

        }
        } catch (Exception e) { 
        out.print(e);

    }