On a web application for accounting services, I have the good old Invoice. To keep this example as simple as possible, each Invoice has many rows, and each row has its item with its price.
At the beginning, the prices of the items are read from a PriceList table.
Each time an invoice is emitted, i store the the key of the item of the PriceList table in my InvoiceRows table.
But prices in PriceList table may change (and often do so) so I’ve put a price field in the InvoiceRows table, that will contain a copy of the price.
I’ve managed all this through an ORM (actually i use rails ActiveRecord) but Hibernate would be more or less the same. So my ORM binds some classes, say Invoice and InvoiceRow to the related database tables. Both of them have a save method that persists the data on the database.