name varchar(20),

                            qty int

                   );

                   insert into t_sale(name,qty) values('s1',22);

                   insert into t_sale(name,qty) values('s2',122);

                   insert into t_sale(name,qty) values('s3',242);

                   insert into t_sale(name,qty) values('s4',24);

                   insert into t_sale(name,qty) values('s5',12);

                   注：查询销量前三的产品

                   select * from t_sale order by qty desc limit 3;

                   step2 服务器端程序：

                            写一个Servlet，通过dao查询t_sale表，

                   将查询得到的数据转换成json字符串，然后

                   发送给客户端

                   step3 测试服务器程序

                   step4 客户端的程序