A little invoicing application developed writing only 4 simple Java classes: Customer, Invoice, InvoiceDetail and Product.
A complete ERP with finance, human resources, payroll, inventory management, sales, work orders, business intelligence, reports, etc. This is a commercial product developed by Sicflex using OpenXava and XavaPro.
This OpenXava demo has user login, hierarchical menu, multitenancy, users and roles management, and advanced security. It uses XavaPro.