路径：src/main/resources/application.properties

    配置样例：

    1. #服务设置
    2. server.port=8080
    3. server.servlet.context-path=/exam
    5. #MySQL配置
    6. spring.datasource.url = jdbc:mysql://localhost:3306/DatebaseName（自己数据库名）
    7. spring.datasource.username = root
    8. spring.datasource.password = 123
    9. spring.datasource.driverClassName = com.mysql.jdbc.Driver
    10. spring.datasource.max-active=20
    11. spring.datasource.max-idle=8
    12. spring.datasource.min-idle=8
    13. spring.datasource.initial-size=10