此类负责管理数据库连接，包括建立初始连接和创建演示应用程序要访问的ProductDAO实例。

This class is responsible for managing the database connection, which includes establishing the initial connection and creating a ProductDAO instance for the demo application to access.

youdao

此类负责管理数据库连接，包括建立初始连接和创建演示应用程序要访问的ProductDAO实例。

This class is responsible for managing the database connection, which includes establishing the initial connection and creating a ProductDAO instance for the demo application to access.

youdao