无需单击提交按钮即可获取表单值

朋友，您好，我正在处理一个JSP文件，其中有3个组合框，分别名为category，sub category&.等级.选择某个类别后，我想立即显示相应的子类别&数据存储区中相应组合框中的级别.我也使用了this.form.submit()方法，但是它无法正常工作.有人可以建议我其他方法吗?
这是我的代码.

Hello friends,I am working on a JSP file in which I have 3 combo boxes named category, sub category & level. As soon as I select some category, I want to display the corresponding sub category & level in the respective combo-box from the datastore. I used this.form.submit() method for the same but it is not working properly. Can someone suggest me some another way of doing it?
This is my code.

<tr>
<td><h2><Font color=#003366>

Category</Font></h2></td>
<%
String category="";
%>

<td> <select name="quizname" onChange="this.form.submit();">
<Option>--Select--</Option>
<%
for(Quiz q : quiz)
{
%>
<Option name="quizname"><%=q.getCategory()%></Option>
<%
}
%>
</select>
</td></tr>
<tr></tr>
<tr>
<td><h2><Font color=#003366>Subcategory</Font></h2></td>
<td><select name="subcategory">
<%
for(Quiz q : quiz)
{

    if(q.getCategory().equals(request.getAttribute("category")))
    {
        %>

<Option name="subcategory"><%=q.getSubCategory()%></Option>
<%
}
}
%>
</select>

</td></tr>
<tr></tr>
 <tr>
<td><h2><Font color=#003366>Level</Font></h2></td>
<td><select name="level">
<%
for(Quiz q : quiz)
{
    //if(category.equals(q.getCategory()))
    //{
    if(q.getCategory().equals(request.getAttribute("category")))
    {
        %>


<Option name="level"><%=q.getLevel()%></Option>



<%
}
}
%>
</table>
</select>

</td></tr>
<p>&nbsp;</p>
<INPUT TYPE=hidden NAME="email" VALUE=<%=user.getEmail() %>>
 <tr><td><input type="submit" value="Start Quiz"/>
</td></tr>

预先感谢.

Thanks in advance.