字符编码不一致：ERROR：Caused by: java.sql.SQLException: Unknown initial character set index ‘255’ received f

ERROR：Caused by: java.sql.SQLException: Unknown initial character set index ‘255’ received from server. Initial client character set can be forced via the ‘characterEncoding’ property.
是characterEncoding字符编码数据库和IDEA不一致造成的
只需要在你的Url后面加上?characterEncoding=utf8或者在将数据库改为和Idea字符编码一致即可

//testjdbctemplate为你的数据库名称
Url("jdbc:mysql://localhost:3306/testjdbctemplate?characterEncoding=utf8");