Unknown initial character set index '255' received from server. 问题解决

出现这个问题应该是因为字符集编码方式有问题
所以在JDBC连接的url后面加上“?useUnicode=true&characterEncoding=utf8”就可以了

比如
Connection conn = DriverManager.getConnection(“jdbc:mysql://localhost/student?useUnicode=true&characterEncoding=utf8”, “root”, “123456”);

文章来源: https://blog.csdn.net/justinzwd/article/details/88846187