当你看到这样的错误：
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet successfully received from the server was 19 milliseconds ago. The last packet sent successfully to the server was 19 milliseconds ago. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at com.mysql.jdbc.Util.handleNewInstance(Util.java:425) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:989) at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:164) at com.mysql.jdbc.MysqlIO.negotiateSSLConnection(MysqlIO.java:4898) at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1659) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1226) at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2253) at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2104) ... 13 more 也许你第一会想到什么配置数据库 wait_timeout大于8小时，但是如果设置后也不行，而且这是在普通的main方法中一个简单的数据库连接（进行一次全新的连接，非程序运行期连接池错误），那么你不妨换一下数据库驱动版本。
