OpenSource проекты на Java

Java

https://github.com/alkacon/opencms-core
https://github.com/jirkapinkas/example-eshop-vaadin
https://github.com/jirkapinkas/jsfeshop

Spring Framework

[Udemy] Building An E-Commerce Store Using Java Spring Framework [ENG, 2016]

https://github.com/webmakaka/Building-an-e-commerce-store-using-java-spring-framework

[Книга] Spring MVC. Alex Bretet - Spring MVC Cookbook - 2016

Исходные коды:
https://github.com/alex-bretet/cloudstreetmarket.com

Кислин Григорий

https://github.com/JavaOPs/topjava

Oracle ADF

http://oracle-adf.com/src/