code: public void setUserAttribute(final String _key,
                                   final String _value,
                                   final UserAttributesDefinition _definition)
          throws EFapsException
      {
          if (containsSessionAttribute(UserAttributesSet.CONTEXTMAPKEY)) {
              ((UserAttributesSet) getSessionAttribute(UserAttributesSet.CONTEXTMAPKEY)).set(_key, _value, _definition);
          } else {
              throw new EFapsException(Context.class, "getUserAttributes.NoSessionAttribute");
          }
      }
docs: Set a new UserAttribute for the UserAttribute of the Person this
  Context.The UserAttributes are stored in the {@link #sessionAttributes}
  Map, therefore are thought to be valid for one session.
  
  @param _key Key of the UserAttribute
  @param _value Value of the UserAttribute
  @param _definition Definition
  @throws EFapsException on error