server.port=8080
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:8080/db?serverTimezone=Asia/Shanghai&useSSL=false&characterEncoding=utf-8
mybatis.configuration.map-underscore-to-camel-case=true
配置好properties后启动springboot连接不上数据库，报错如下：
Error updating database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.] with root cause
查了很多也没法解决，用户名密码正确，数据库名称正确，就是连接不上。。
