[Struts2] generating ActionErrors in the Action?

[Sébastien LABEY]

Hi,
I was using Struts 1.x before and I was used to generate ActionErrors (that
contains ActionError) from the errors returned by my 3rd party side (my own
framework to access DB). But with Struts 2, I cannot find how to build these
ActionErrors / ActionError... what are now the class to deal with errors
that I can build myself? Can someone help me?
Thanks in advance.
Sebastien