BeanShell is a little Java interpreter, it accepts standard Java syntax as well as loose types, commands and method closures. For more information on BeanShell visit: http://www.beanshell.org/.

In the Flux Designer you are able to write code in the pre and post scripts of an action. You can use Java or you can use BeanShell (Flux defaults to BeanShell) to incorporate little snippets of code into the your graphically designed flow charts.