解决方案如下：
     1、在dos环境下，用mysql --default-character-set=gbk -u root -p 这句话进入mysql~~
     2、建数据库、表，如下：
       
create database admin;
           use admin;

           CREATE TABLE admin (
           admin_name char(20) NOT NULL,
           admin_password char(20) NOT NULL
           ) TYPE=MyISAM,
           default character set gbk;  

     3、接着用如下testgbk.jsp测试，
<%@ page contentType="text/html; charset=gbk" language="java" import="java.sql.*" import="java.io.*" %>
<%  
Connection conn = null;
Class.forName("com.mysql.jdbc.Driver");  
conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?user=root&password=123456&useUnicode=true&characterEncoding=gbk");
Statement stmt=conn.createStatement();
ResultSet rs=null;
%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<title></title>
</head>
<body>
<table width="314" height="34" border="0" align="center" cellpadding="0" cellspacing="0" bgcolor="#6666FF">
  <tr>  
    <td align="center" height="19" width="100" style="font-size:10pt;color:red;">帐号</td>
    <td align="center" height="19" width="40" style="font-size:10pt;color:red;">密码</td>
  </tr>  
<%  
String temp = "insert into admin(admin_name,admin_password) values('你们好','123')";
PreparedStatement pst = conn.prepareStatement(temp);
pst.executeUpdate();
pst.close();
//结束
temp = "select * from admin";
rs=stmt.executeQuery(temp);
while(rs.next()){
String admin=rs.getString("admin_name");
String pass=rs.getString("admin_password");
%>
  <tr>  
    <td align="center" height="19" width="100" style="font-size:10pt;color:blue;"><%=admin%></td>
    <td align="center" height="19" width="40" style="font-size:10pt;color:blue;"><%=pass%></td>
</tr>  
<%
}
%>
<%  
rs.close();
stmt.close();
conn.close();  
%>
  <tr>  
    <td height="19" colspan="4" align="center" style="font-size:10pt;color:red;"> </td>
  </tr>
</table>
</body>
</html>