jdbc 连接MySQL 一直报错
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet successfully received from the server was 253 milliseconds ago.  The last packet sent successfully to the server was 248 milliseconds ago.

jdbc:mysql://a.b.c.d:3306/testdb?verifyServerCertificate=false&useSSL=true

telnet mysql 3306 端口 ok ,说明网络没问题

怀疑 jdbc 驱动问题

mysql:mysql-connector-java:5.1.30

升级到 5.1.47  连接ok