Start the DB.
Verify if mysqld is started without the --skip-networking option.
Restart the DB and fix your code accordingly that it closes connections in finally.
参考：
http://stackoverflow.com/questions/2983248/com-mysql-jdbc-exceptions-jdbc4-communicationsexception-communications-link-fai
http://blog.csdn.net/gucapg/article/details/17509969
http://4925054.blog.51cto.com/4915054/1154263