说明：  JDBC与JNDI的区别 :没有JNDI的做法存在的问题：1、数据库服务器名称MyDBServer 、用户名和口令都可能需要改变，由此引发JDBC URL需要修改；2、数据库可能改用别的产品，如改用DB2或者Oracle，引发JDBC驱动程序包和类名需要修改；3、随着实际使用终端的增加，原配置的连接池参数可能需要调整；4、
(The difference between JDBC and JNDI: No JNDI approach problems: one, the database server name MyDBServer, user name and password may need to change, resulting in a need to amend the JDBC URL 2, the database may be to switch to other products, such as switch DB2 or Oracle, triggered JDBC driver package and class names need to be amended 3, with the actual use of terminals increases, the original configuration of the connection pool may need to adjust parameters 4,)