无法使用servlet将数据添加到数据库中以获取crud

Question

<form  action="addCustServlet" method="POST" name="frmAddUser">
        <table>
          <tr>
            <td><h3 class="templatemo-gold">ID Number: </h3></td>
            <td>
            <input type="text" name="cust_id" size="12" value="<c:out value="${customer.cust_id}" />" /> <br/><br/></td>
            </tr>
            <tr>
            <td><h3 class="templatemo-gold">Name: </h3></td>
            <td><input type="text" name="custName" size="50" 
            value="<c:out value="${customer.custName}" />" /> <br/><br/></td>
            </tr>
            <tr>
            <td><h3 class="templatemo-gold">Address: </h3></td>
            <td><input type="text" name="custAdd" size="50"
				value="<c:out value="${customer.custAdd}" />" /><br/><br/></td>
            </tr>
            <tr>
            <td><h3 class="templatemo-gold">Region: </h3></td>
            <td><input type="text" name="custRegion" size="50" 
            	value="<c:out value="${customer.custRegion}" />" /><br/><br/></td>
            </tr>
            <tr>
            <td><h3 class="templatemo-gold">Handphone No: </h3></td>
            <td><input type="text" name="custHandphoneNo" size="50" 
            	value="<c:out value="${customer.custHandphoneNo}" />" />><br/><br/></td>
            </tr>
            <tr>
            <td><h3 class="templatemo-gold">Phone No: </h3></td>
            <td><input type="text" name="custPhoneNo" size="50" 
            	value="<c:out value="${customer.custPhoneNo}" />" /><br/><br/></td>
            </tr>
            <tr>
            <td><h3 class="templatemo-gold">Email:  </h3></td>
            <td><input type="text" name="custEmail" size="50" 
            	value="<c:out value="${customer.custEmail}" />" /><br/><br/></td>
            </tr>
            <tr>
			<td> <input type="submit" name="submit" class="btn text-uppercase templatemo-btn templatemo-info-btn">Submit </td>
			
          </tr>
          </table>
			</form>

每当我尝试使用jsp表单插入数据时，它会一直执行nullPointerException，因为我的cust_id不会自动生成或自动递增。 单击addbutton后，servlet发送到updateUser，无法插入数据。

    Customer customer = new Customer();
    customer.setCustName(request.getParameter("custName"));
    customer.setCustAdd(request.getParameter("custAdd"));
    customer.setCustRegion(request.getParameter("custRegion"));
    customer.setCustHandphoneNo(request.getParameter("custHandphoneNo"));
    customer.setCustPhoneNo(request.getParameter("custPhoneNo"));
    customer.setCustEmail(request.getParameter("custEmail"));
    String cust_id = request.getParameter("cust_id");
    if(cust_id == null || cust_id.isEmpty())
    {
        dao.addUser(customer);
    }
    else
    {
        customer.setCust_id(cust_id);
        dao.updateUser(customer);
    }
    RequestDispatcher view = request.getRequestDispatcher(LIST_USER);
    request.setAttribute("customer", dao.getAllCustomer());
    view.forward(request, response);
}