Hi John,
John Fereira wrote:
> I have been using XStream for quite a while without a hitch but recently
> was presented with a use case that I'm not sure how to resolve.
> Essentially I have an Hours object that represents the opening and closing
> hours of a location. The actual open/close fields are "Time" objects
> that uses a Calendar instance on the back end. Up until recently the
> open/closed Time objects were always instantiated to a non-null value.
> However, for reasons that I don't necessarily agree with I've been asked
> to set the open/closed Time objects to a null if a flag (another field in
> the Hours object) has been set to "closed all day" or "open all day".
> The issue that I'm having is that I want to serialize the Hours object
> and marshall a "openTime" element (with the time set to null) even when
> the Time object is null. I've got a "TimeConverter" class that returns
> true for the canConvert method (it is recognizing that a Time.class is
> being handled) but it doesn't appear that the marshal method is being
> called if the Time object is a null.
As you already found out, this does not work. Most XStream converters will
omit any null objects at all. The reason is that XStream has to separate
between objects that may be represented by an empty string and null values
itself.
In your case I simply assume that Hour is handled by the ReflectionConverter
that will not do anything for fields with null values. Therefore your
TimeConverter is not called, because no XML node has been generated.
The simplest solution is to write a custom converter for your Hour type.
Then your free to write whatever you like into the XML representation for
your null values. Have a look at the converter tutorial to see how you may
forward the conversion for the individual fields of the Hour type to XStream
again.
Another approach is to use a constant static placeholder representing the
NULL Time. You may identify that object in your TimeConverter and
getter/setter of your Hour type must translate null into this placeholder.
Regards,
Jörg
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