Update Combo box choice

Question

I have written the below code. When "Equipment1_combo" is selected, the respective choice will be update into the "Equipment1_pcs". E.g. if I chose "Racket", it show the quantity from 0 to 12 (assume that the equipment_inventory dB have 12 as quantity of racket).
<%
Connection dbcon2;
Statement statement2;
Statement statement3;
ResultSet rs2;
ResultSet rs3;
//connect to DB
try
String driver2 = "com.mysql.jdbc.Driver";
String dbURL2 = "jdbc:mysql://localhost/fyp";
Class.forName(driver2).newInstance();
dbcon2 = DriverManager.getConnection(dbURL2);
System.out.println("Connection to database is successful");
catch(ClassNotFoundException e)
System.out.println("Database driver could not be found.");
System.out.println(e.toString());
throw new UnavailableException(this, "Database driver class not found");
catch(SQLException e)
System.out.println("Error connecting to the database.");
System.out.println(e.toString());
throw new UnavailableException("Cannot connect to the database");
statement2 = dbcon2.createStatement();
     rs2 = statement2.executeQuery("SELECT DISTINCT CATEGORY from EQUIPMENT_INVENTORY ORDER BY CATEGORY ASC");
     statement3 = dbcon2.createStatement();
     rs3 = statement3.executeQuery("SELECT QUANTITY from EQUIPMENT_INVENTORY where CATEGORY='"+request.getParameter("Equipment1_combo")+"' ");%>
<p><b>Reserve Equipment </b></p>
<p><b><i>Equipment 1</i></b>   
<select name="Equipment1_combo">
<% while (rs2.next()) {%>
<option value = "<%=rs2.getString("Category")%>"><%=rs2.getString("Category")%></option>
<%}%>
</select>    No. of pieces   
<select name="Equipment1_pcs">
<% while (rs3.next()) {%>
<option value = "<%=rs3.getString("Quantity")%>"><%=rs3.getString("Quantity")%></option>
<%}
rs3.close();
%>
</select></p>

Answer 1

Right then.
JSP is a server side language. All the code gets run at the server, and returned to the client as an HTML page. The only method of communication you have to the server is by submitting an html form.
Therefore jsp code can not react to events on the form such as selecting an item from the list directly.
There are 2 options
1 - javascript - handles client side interaction with a web page - use javascript/vbscript to change the values in the combo.
2 - when they select an item in the list, resubmit the form with that parameter, and generate the jsp accordingly (ie reload the page)
This is not an uncommon question. Do a quick forum search and you come up with plenty of related posts
Check out these links
http://onesearch.sun.com/search/developers/index.jsp?col=devforums&qp=&qt=combo+jsp+javascript+select+dynamic
http://forum.java.sun.com/thread.jsp?forum=54&thread=203309
http://forum.java.sun.com/thread.jsp?forum=45&thread=145694