This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
you have notmentioned technology to be used for eCommerce application.
Assuming since you have used Javaranch to post your question, you are looking for Java based eCommerce solution.
You can use BroadLeaf Commerce solution (http://www.broadleafcommerce.org/). It is an open source Spring MVC based ecommerce tool. By the way , this tool has sample Coffee/Restuarant application which can be a very good point to start.
Oracle certified Java 8 Programmer I (1Z0-808), Oracle Java Web Service Developer (1z0-897), Oracle certified Java 7 Programmer, SCJA 1.0, SCJP 5.0, SCWCD 5.0, Oracle SQL Fundamentals I, CIW Certified Ecommerce specialist