Easy to install data source?

Hello all!

What kind of a data source would be the easiest to use, when it comes to a lightweight app with very little customisations?
The goal is to have a webapp load the rows visible to a table, and be able to at least add rows (the lower one in the pic).
XML? SQL DB?

Thank you!

To toot my own horn, IRC channel #vaadin pointed me towards using JPAContainer.