在数据库操作时连接数据路例程中，数据库驱动能加载成功，但数据库连接报错。

如下所示：请问一下哪里出现了错误

数据库驱动加载成功  

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)

at java.lang.reflect.Constructor.newInstance(Unknown Source)

at com.mysql.jdbc.Util.handleNewInstance(Util.java:400)

at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1038)

at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:339)

at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2247)

at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2280)

at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2079)

at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:794)