Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 78,050,512 milliseconds ago.

今天访问已经架上服务器的网站，报错：

   Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: 
   The last packet successfully received from the server was 78,050,512 milliseconds ago. 
   The last packet sent successfully to the server was 78,050,512 milliseconds ago. 
   is longer than the server configured value of 'wait_timeout'. 
   You should consider either expiring and/or testing connection validity before use in your application,
   increasing the server configured values for client timeouts,
   or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.  
   翻译过来：上次访问时，发送的包已经多少多少秒了，比设置的‘wait_timeout’要长，建议修改 autoReconnect=true。

解决方案：
修改或添加三个参数：

将testConnectionOnCheckout 设为 false
将testConnectionOnCheckin 设为 true
将idleConnectionTestPeriod 设为 30，这个数字要根据项目情况设定，比8小时小就好

具体原理参考：https://blog.csdn.net/frankcheng5143/article/details/50589264