项目使用ojdbc14.jar连接oracle11.2数据库，但是升级到oracle12c后，出现ORA-28040的异常。
解决办法是：在12c的network/admin/sqlnet.ora文件里，添加一行兼容的版本号即可。
SQLNET.ALLOWED_LOGON_VERSION=8
如下：
# sqlnet.ora Network Configuration File: c:\app\hanch\product\12.1.0\dbhome_1\network\admin\sqlnet.ora
# Generated by Oracle configuration tools.
# This file is actually generated by netca. But if customers choose to
# install "Software Only", this file wont exist and without the native
# authentication, they will not be able to connect to the database on NT.
SQLNET.AUTHENTICATION_SERVICES= (NTS)
NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)
# ORA-28040: No matching authentication protocol
SQLNET.ALLOWED_LOGON_VERSION=8