XOM API for Processing XML with Java

[Adam Constabaris <adamc AT email.unc.edu>]

I'm writing an application which involves editing DocBook documents that includes a 'pretty 
print' function.  The base Serializer class does a pretty good job of this, but I'd prefer tthe 
output preserve whitespace in some DocBook elements (such as programlisting and screen).  The 
recommended (?) approach is to add the xml:space="true" attribute to the elements on which
I want to preserve space.

Currently, the approach I'm taking involves a subclass of Serializer that overrides 
write(Element) to check to see if the element's localName is on the list of whitespace 
preserving elements, and adds the xml:space="true" attribute to those elements.  This does a 
great job of preserving the whitespace on the specified elements while indenting all the other 
ones.

However, I want the output to be validatable against the DocBook DTDs, which creates a problem 
for me, since the xml:space attribute is not defined in that DTD.

What would be ideal, from a programmatic standpoint, would be to be able to 'virtualize' the 
attribute -- pretend it's there for purposes of whitespace preservation, but don't actually 
output it.  One way I could achieve this (I think) would be to call setPreserveSpace(true) on 
the TextWriter used by Serializer for the 'preserving' elements.  However, the variable has 
private access to Serializer, so I'd have to instantiate my own in my subclass (alarm bell 
one!). At any rate, the TextWriter is package private, so this is definitely not possible for a 
Serializer subclass that doesn't live in the same package (alarm bell two). Even if it is, it 
looks like I might have to override more than the one method (alarm bell three).

So, I'm seeking advice (meaning that I don't have a well-formulated question 
=):

I'm willing to cop that what I'm wanting to do (get the behavior without the markup) may not be 
the best approach in the first place.  My reasons are that it is least surprising to my users 
-- I don't want serialization to alter the document in a radical fashion, beyond the 
prettification.  My users are not, as a rule, interested in the gory details of DocBook to 
begin with.  Secondly, getting the behavior without the markup requires the fewest changes 
elsewhere in the system.  I'm all ears if anybody has any advice on this point.

I suppose I could pretty print the original document, adding the attributes, then read the 
result into a new XOM document,  stripping the unrecognized-by-the-DTD attributes, and 
serialize that output without pretty printing, but I'm not sure even Rube Goldberg would be 
happy with that approach.

For gory technical reasons, I'm unable to use W3C DOM for pretty printing (bugs in pre-5.0 JVMs 
mean that the DOM building classes don't call resolveEntity() (!) and I need to use an entity 
resolver), and the application delivery method -- Web Start -- doesn't let me override core 
JAXP classes).


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Adam Constabaris
ITS Knowledge Management
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