原来数据库5.5升级到8.0后，数据库连接配置没有改造成的

用的依赖

<dependencies><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.11</version></dependency>
</dependencies>	

url中加上“useSSL=false”。否则报错“Establishing SSL connection withoutserver's identity verification is not recommended. According to MySQL 5.5.45+,5.6.26+ and 5.7.6+ requirements SSL connection must be established by defaultif explicit option isn't set. For compliance with existing applications notusing SSL the verifyServerCertificate property is set to 'false'. You needeither to explicitly disable SSL by setting useSSL=false, or set useSSL=trueand provide truststore for server certificate verification.”
url中加上“serverTimezone=GMT%2B8”（GMT%2B8代表东八区）否则会报关于时区的错

最终的配置文件

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql:/localhost:3306/mysql?characterEncoding=utf8&useSSL=false&serverTimezone=GMT%2B8
spring.datasource.username=root
spring.datasource.password=yourpassword