[jdom-interest] XML document transfer performance

[Dennis Sosnoski]

XMLS is more designed for document transfer than for persistence. It should be
fine to use between different versions of JDOM (or between JDOM and one of the
other models, since it doesn't use model-specific information), but for general
persistence you'd probably still want to have standard Java serialization
supported.

One example is a user subclassing the objects and adding associated information.
Standard serialization handles this, but XMLS does not because it's purely an
XML document representation. Other issues would include things such as adding
DTD/schema information to the document representation.

It'd be better to make XMLS usable for Java serialization without eliminating
the option of default serialization. I think this can be done pretty easily by
using a wrapper class: XMLSWrapper is given an instance of Document (or
Element), and implements Externalizable. When XMLSWrapper is serialized it
generates XMLS for the document, and when restored it reads XMLS to rebuild the
document. I'll add this type of wrapper to the .9 release, due out at the end of
October.

Even easier, from the user standpoint, would be to add an XMLSDocument subtype
of Document. This does the same thing as XMLSWrapper, but does it transparently
- if you create an XMLSDocument you'll *always* use XMLS for serialization.
Users who want to be able to use default serialization instead just use the
normal Document. The wrapper alternative would still be possible for when they
wanted to use XMLS.

I'll add a section on plans for the next release to the site tonight. If there's
enough interest I'll move the project to SourceForge where there can be more
discussions and parallel development.

  - Dennis

Alex Rosen wrote:

> This looks very cool! It's nice to see support for both dom4j and JDOM.
>
> I wonder if this could be JDOM's native serialization format? What do you
> think about the long-term compatibility of this format? (I don't think that
> people should be using anything besides standard XML files for long-term
> persistence, but as Jason pointed out, we do need to let different versions
> of JDOM talk to each other via RMI.)
>
> Alex