This week's book giveaway is in the Reactive Progamming forum. We're giving away four copies of Reactive Streams in Java: Concurrency with RxJava, Reactor, and Akka Streams and have Adam Davis 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 JPA Developer (1Z0-898),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