Populating one drop down based on the other

[sree visu]

I am using JSTL to populate one dropdown based on the selection of the other dropdown

Here is what i did:

In the form element tag i have a drop down named manufact that gets populated(and works correctly).But i would like to get the selected value of this dropdown and
populate the second drop down named providedfor.I have used the window.location.reload which reloads the form.But i don't understand why the <sql:param> tag does not get filled with the value of the
param.manufact ( as shown by numbering (1) and (2).Is there any mistake? Please help

The HTML form elements:

<tr> 
                    <td  class="row1"><span>Manufacturer: *</span></td>
                    <td class="row2"><select name="manufact"  onchange="window.location.reload()" value="${param.manufact}">-----------------------------------------(1)
                            
                            <option default>Select</option>
                            <c:forEach var="company" items="${companies.rows}">
                                    <option><c:out value="${company.comp_name}"/></option>
                            </c:forEach>
                        </select>
                    </td>
					
                </tr>
				<td><br/></td>
                 
				<tr> 
                    <td  class="row1"><span>Service Provided for : *</span></td>
                    <td class="row2"><select name="providedfor">
                            <option default>Select</option>
                            <c:forEach var="gad" items="${gadget.rows}">
                                    <option><c:out value="${gad.gad_name}"/></option>
                            </c:forEach>
                        </select>
                    </td>

Now the JSTL sql tags

<sql:setDataSource var="dataSource" driver="com.mysql.jdbc.Driver"
                       url="jdbc:mysql://localhost:3306/gadgets"  user="sree" password="sree"  scope="session" />

    <sql:query var = "companies" dataSource="${dataSource}">
       select comp_name from company
    </sql:query>

    <sql:query var = "gadget" dataSource="${dataSource}">
        SELECT distinct gadget_info.gad_name  FROM company, gadget_info where gadget_info.comp_id IN (select company.comp_id from company where company.comp_name=? 
        <sql:param value="${param.manufact}"/> );-------------------------------------------------------------------------------------------(2)
    </sql:query>

Thanks for your help in advance

[Bear Bibeault]

Personally, I would use an Ajax solution for this, and would never use the SQL JSTL tags.

[sree visu]

Thank you bear bibeault,
but i am a newbie to ajax and i am not clear in its concepts.Could you please tell me how to do it with JSTL and SQL tags.To be the minimum how would you save a particular form element after it is getting reloaded so that i can use it in my (2) as mentioned in my previous post.Sorry that i do not know ajax and it is not an issue if my form gets reloaded.Please help me to fix it...

[Bear Bibeault]

The SQL tags are not intended for production use and I do not think you should be relying upon them.

If you want to use a pure JSP solution (rather than Ajax), that's fine (just less efficient), but you should do so by following best practices and sequestering any DB access to Java model classes.

[Bauke Scholtz]

If Ajax is one step too high and you want to do it all asynchronously, then just print all possible options out into a Javascript array variable and use Javascript to populate the dropdown.

[sree visu]

Thank you Bauke Scholtz and Bear Bibeault for your reply