求教jsp useBean bean的问题 - Java / Web 开发

比如说DB.class是在包com/zhl/jdbc下的
那么DB.class放在什么地方 如果用<jsp:useBean id="d" class=""/>来引入bean 那么class属性应该怎么写
需不需要像servlet那样还要配置web.xml的<servlet-mapping> 

<%@page import="java.io.*,java.sql.*"%>
<%@page contentType="text/html; charset=GBK"%> 
<jsp:useBean id="DB" class="com.zhl.jdbc.ExecuteDB"/>

<%
String sql = "select id,title from zhuye order by id desc";
int i=0;

Connection conn = DB.getConnection();
PreparedStatement ps = conn.prepareStatement(sql);
ResultSet rs = ps.executeQuery();
%>
<table valign="top" Cellspacing="5">
<%
while(rs.next()){
int id = rs.getInt("id");
String s = rs.getString("title");
%>
<tr>
<td valign="top"><h5><%=id+" "%></h5></td>
<td valign="top"><h5>><a href=left_dianHouWen.jsp?id=<%=id%> ><%=s %></a></h5></td>
</tr>
<%
i++;
if(i>10) break;
}
DB.free(rs,ps,conn);
%>
</table>

像上面那样写的话 运行的时候出错
org.apache.jasper.JasperException: javax.servlet.ServletException: java.lang.NoClassDefFoundError: com/zh