错误日志：

java.sql.SQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:110)
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89)
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63)
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:73)

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
	at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
	at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91)
	at com.mysql.cj.NativeSession.connect(NativeSession.java:152)

原因：

数据库链接失败了，检查发现是数据库服务器被删了，纯纯的删库跑路啊，重新装个环境就好了。