오류 원인 : MySQL 드라이버가 이전 버전
해결 방법 : 새로운 버전의 MySQL 드라이버로 교체

2023-04-21 10:26:14.014  INFO 22536 --- [ restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/]  : Initializing Spring embedded WebApplicationContext
2023-04-21 10:26:14.014  INFO 22536 --- [ restartedMain] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 2171 ms
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
2023-04-21 10:26:14.841  INFO 22536 --- [ restartedMain] o.s.b.d.a.OptionalLiveReloadServer  : LiveReload server is running on port 35729
2023-04-21 10:26:14.914  INFO 22536 --- [ restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 80 (http) with context path

-- maven 사용자의경우 (버전업하면됨)

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.13</version>
        </dependency>