XOM API for Processing XML with Java

[Wolfgang Hoschek <whoschek AT lbl.gov>]

> Wolfgang Hoschek wrote:
>
> > Another, unrelated thing to note is that JDK 1.5 nomore does 
> > String.subString() sharing. It's good news since it can eliminate 
> > hidden memory leaks, and it's bad news since it can produce tons of 
> > memory overhead where code implicitly assumes that substrings are 
> > shared. For example, Element.prefix and Element.localName come to my 
> > mind. Even if a prefixed qname is constant, new copies are generated 
> > by the internal design of Element, and, worse, semi-permanently 
> > stored in Element. Same for Attribute.
>
> Oh crap. This is what I hate about optimization. You get it just 
> right, and then everything changes. Does this mean I should be calling 
> intern on the prefixes and local names? Or does substring at least do 
> that in 1.5?
>
> I'll look at this, but I'm not going to make any 1.5 specific 
> optimizations for at least the next few months. Right now the prime 
> target is Java 1.4. Sometime down the road, I'll think about targeting 
> 1.5 instead.

Yep, taking care of the substring issue for 1.5 would require a lot 
more invasive internal changes than anything we've been talking about 
so far, so delaying that until a good scheme comes to light and proves 
itself seems the best approach.

Calling String.intern() is not a good idea, IMHO. intern() has lots of 
problems, it's very slow (native method that jumps back and forth many 
times between native and java code for each call. Interned strings may 
never be garbage collected, if you're out of luck, etc. Might be better 
to consider an application level string pool, per XOM document, taking 
care of qnames, URIs, etc., perhaps a little along the lines of the 
string pool internally used by bnux.

Another approach might be to just store qnames directly, and compute 
rather than store prefix and localName. Would probably lead to 
internally rewriting quite a few XOM methods, e.g. in the 
nu.xom.Serializer

With some more though once could find other lines of attack as well, 
i'm sure.

Wolfgang.