An important part of the development is to provide an interactive interface for the submission of new puzzles.   This brought me up against the GWT default setup which is only really meant to have one window.

If you want to store things beyond the lifetime of a single instance of a program then you use a database.   If you want to write programs nowadays then you use an object oriented language and work with objects.   If you want to do both then you need an object database in which to store the objects.   Most people do this with an object-relational mapping (ORM) which store the objects in a relational database but still maintains their connectivity and identity as objects.   Hibernate is one such ORM technology.

An important step in any development is the installation and configuration of the development tools needed to do the work.

The functionality I wanted for my interactive puzzle solving interface together with the requirement that it run in most browsers pretty much forced the choice of asynchronous JavaScript and XML (AJAX) or JSON.   This allows a web page to communicae with the server and act on the response without doing a reload of the whole page.