Sets the value of the form session attribute named by attributeName. See #getFormSessionId() for
information on form sessions.
Note that getFormSessionAttribute() returns the state of the object at the time of calling this method, any changes made to the saved object after calling this method
will not be reflected in the object returned by getFormSessionAttribute().
attributeName. See #getFormSessionId() for information on form sessions.Note that getFormSessionAttribute() returns the state of the object at the time of calling this method, any changes made to the saved object after calling this method will not be reflected in the object returned by getFormSessionAttribute().