java.sql.SQLException: Unknown initial character set index ‘255‘ received from server.

控制台报错：

com.alibaba.druid.support.logging.JakartaCommonsLoggingImpl error
严重: create connection SQLException, url: jdbc:mysql://localhost:3306/userDb, errorCode 0, state S1000
java.sql.SQLException: Unknown initial character set index '255' received from server. Initial client character set can be forced via the 'characterEncoding' property.

把jar包从mysql-connector-java-5.1.7-bin.jar
换成mysql-connector-java-8.0.11.jar，问题解决