刚学mybatis，测试的时候有异常：
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.
去检查数据库的数据，有汉字
就在url后面加上了"?characterEncoding=utf8"之后就可以正常显示了。
Unknown initial character set index '255' received from server
原文：https://www.cnblogs.com/xsyz/p/13152684.html