写成下面这样就行:
Manifest-Version: 1.0
Main-Class: dandan.index
Class-Path: ./lib/mysql-connector-java-8.0.17.jar
注意Class-Path路径
然后在jar包的路径下创建/lib文件夹,然后把mysql-connector-java-8.0.17.jar防盗lib文件夹中