在linux下，开发一个web应用，期间调用数据库时总是不成功，如果单独写一个类，并编译执行访问数据库，正常，但是用web应用来调这个类连接数据库，就会出现错误：com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.security.AccessControlException
1、Caused by: com.MySQL.jdbc.exceptions.jdbc4.CommunicationsException:
The last packet successfully received from the server was 56,201,339 milliseconds ago. The last packet sent successfully to the server was 56,201,339 milliseconds ago. is longer
