java.sql.SQLException: The server time zone value '�й���׼ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.

这个错误是因为mysql连接的依赖包是高版本的情况下：

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>6.0.6</version>
</dependency>

在配置datasource.url时不能简单的这样配：

spring.datasource.url=jdbc:mysql://localhost:3306/chat

需要加上一些必要的后缀信息（改成下面的配置就可以了）：

spring.datasource.url=jdbc:mysql://localhost:3306/chat?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC

//修改jar版本也可以解决这个问题

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.22</version>
</dependency>