使用MySQL5.7以下

driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost:3306/demoproject?useUnicode=true&useSSL=false&characterEncoding=utf8

mysql5.7以上的版本

driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/demoproject?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai