Combox box

Question

I am Having the Combox Bov. the values from the combox is driven from thedatabase. that is product id. And when the user selects the product it should the poduct name from the name withot refresh the page in the textbox which i have .. could u please tell
<form name="form" action="Addpdt" method="post">
<table border="0" >
<tbody>
<tr>
<td><b>Store Id</b></td>
<td><select name="sid">
<%
try {
String a1 = null;
String pname = null;
int count = 0;
rs = st.executeQuery("select distinct sid from store_db");
while (rs.next()) {
a1 = rs.getString("sid");
count = Integer.parseInt(a1);
count++;
%>
<option><% out.println(a1);%></option><%}%>
</select></td>
</tr>
<tr>
<td><b>Product Id</b></td>
<td><select id="combo2" onchange="getComboBoxValue('combo2')"> // the is product id. from database....
<%
rs = st.executeQuery("select pid from main_db");
while (rs.next()) {
String a2 = rs.getString("pid");
%>
<option><% out.println(a2);%></option><%}%>
</select></td>
</form>
</tr>
<tr>
<td><b>Product Name</b></td>
<td><input type="text" name=pname /></td> ///// here i need to print the value for the combox which the user selected and got from the database... using the javascript
</tr>
<tr>
<td align="center"><input type="submit" name="addpdt" value="Submit" onclick=""/>
<input type="reset" value="Cancel" /></td>
</tr>
</tbody>
</table>
<%} catch (Exception ex) {
ex.printStackTrace();
%>
</form>

Answer 1

Javascript cannot communicate with your database.
The only way to execute another query is to run java code, which means making a request.
With this sort of page you either need to
1 - load all the possible values into the HTML on the page right at the start. You then have the values in javascript, can set the appropriate value on the javascript event. That works ok for small datasets (<100 entries)
2 - reload the page executing the query for the textfield
3 - use an AJAX call. That is a request to the server, that returns just the information you want. You then use javascript to put that information onto the page in the appropriate place. I would suggest you search the net for examples, there are hundreds around.
Also, just as general convention for writing JSPs
- avoid scriptlet code if possible, and use JSTL instead.
- avoid database code in jsps. For anything other than the most trivial applications, a data access layer composed of java objects is preferable.
Cheers,
evnafets