想做一个根据下拉框中的选择个数，显示文本框的个数，但是总是有问题（偶是菜鸟，请大家多多关照）！
<%@ page contentType="text/html; charset=utf-8" language="java" import="java.sql.*" errorPage="" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
</head>
<%!int bb;%>
<body>
<form action="" name="myform">
<table width="780" border="0" cellspacing="1" cellpadding="0">
<tr>
<td><div align="center"><span class="style2">Please choose the parameter of the period： Year of Period</span>
<input type="text" name="t" value="2009"/>
NO
<select name="aa" onchange="myform.submit()">
<option value="" selected>please choose</option>
<option value=1>1</option>
<option value=2>2</option>
</select>
</div></td>
</tr>
</table>
</form>
<%bb=request.getParameter("aa");%>
<%
for(int i=1;i<=bb;i++){%>
<%=i%>
<%
}
%>
</body>
</html>
谢谢啦！！
------解决方案--------------------
- HTML code
<%@ page contentType="text/html; charset=utf-8" language="java" import="java.sql.*" errorPage="" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>无标题文档 </title> </head> <%int bb=0;%> <body> <form action="" name="myform"> <table width="780" border="0" cellspacing="1" cellpadding="0"> <tr> <td> <div align="center"> <span class="style2">Please choose the parameter of the period： Year of Period </span> <input type="text" name="t" value="2009"/> NO <select name="aa" onchange="myform.submit()"> <option value="" selected>please choose </option> <option value=1>1 </option> <option value=2>2 </option> </select> </div> </td> </tr> </table> </form> <%String cc = request.getParameter("aa");if(cc!=null&&!cc.equals(""))bb=Integer.valueOf(cc).intValue();System.out.println(bb);%> <% for(int i=1;i <=bb;i++){%> <input type="text" name="a<%=i%>"><% } %> </body> </html>
------解决方案--------------------
问题出在这：
bb=request.getParameter("aa");
1）request.getParameter返回的是个string，bb是int型。必须要转换。
2）第一次进入画面时 request.getParameter("aa")是null。需要特殊处理