This topic is covered here:http://www.broadleafcommerce.org/conflu ... figuration
If you're looking to change the datasource for the demo, then you'll need the project source so you can make changes and rebuild the demonstration war. The key files in the demo to change are:
There is a datasource definition in applicationContext-demo.xml (webDS) that currently uses the HSQL driver. You would need to change this to whatever driver you want to use (MYSQL for example). Note, you would need to include your new driver as a dependency in the pom.xml for the demo as well.
In persistence-demo.xml, you would need to change the hibernate.dialect property to the required value for your database platform as well.
Again, these instructions apply to the demo, you're real-world implementation would likely be different. For example, in the real world, you would likely retrieve the datasource through jndi lookup from the container.