Re: [Freecol-developers] save failure

[Michael P. <mp...@co...>]

Following up my own problem...

On Tue, 26 Aug 2008 21:19:31 Michael T. Pope wrote:
> I am repeatably seeing this failure with current 0.8.0 from svn.
> net.sf.freecol.server.FreeColServer saveGame
> 	WARNING: java.lang.NullPointerException

...caused by this object...

> net.sf.freecol.common.model.FreeColObject toXMLImpl
> 	INFO: toXMLImpl, getXMLElementTagName==null: model.goods.bells
> (model.monarch.colonyGoodsParty) PERCENTAGE 50.0 Tue Aug 26 16:46:52 CST
> 2008

which is a Modifier.  The trouble is that a Modifier is a Feature which is a 
FreeColObject, and Modifier (or Feature) does not supply its own version of 
toXMLImpl(XMLStreamWriter), unlike all the immediate subclasses of 
FreeColObject.  This is not a problem for Feature as it is abstract, but 
Modifiers end up calling FreeColObject.toXMLImpl(), which in turn calls the 
wrong getXMLElementTagName().  Adding the obvious implementation of 
toXMLImpl() to Modifier makes saving work again.

Ability is also a Feature with this problem, although I have not seen it 
triggered.

This could be made robust against recurrence by making 
FreeColObject.toXMLImpl(XMLStreamWriter) an abstract method (indeed, its 
right next to a couple of other routines with a "// TODO: make these 
abstract" comment:-).  AFAICT the existing routine is only ever called in the 
course of the above error.  For the present though I have kept the fix to the 
minimum, being new here.

Cheers,
Mike Pope