XOM API for Processing XML with Java

[Michael Whapples <software AT mdw.onl>]

Interesting about the Java9 compact strings. We recently moved our 
application from Java8 to Java15, and I wasn't aware of the compact 
strings feature.


Michael Whapples

On 20/01/2021 11:39, Michael Kay wrote:
> Interesting.
>
> I imagine it was done for space saving, though that's largely redundant with 
> the changes to the String implementation in Java 9.
>
> I'm interested because we're moving to use of byte arrays (one, two, or three 
> bytes per character) in the Saxon tree implementation, but that's to achieve 
> unicode codepoint addressing for XPath operations like substring(), where 
> UTF-8 doesn't help at all.
>
> Michael Kay
> Saxonica
>
> > On 20 Jan 2021, at 09:01, Michael Whapples <software AT mdw.onl> wrote:
> >
> > Hello,
> >
> > I was recently profiling an application which uses XOM with the intention to 
> > improve performance. I noticed that in a section of code where it does a 
> > reasonable amount of XML manipulation a significant amount was down to calls 
> > to Text.setValue and Text.getValue. I could appreciate setValue may need to 
> > do some validation checks, but I had always thought getValue would have been 
> > a simple getter, the profiling data told me otherwise.
> >
> >
> > I decided to examine the XOM source code to see exactlyt what is being done 
> > in the Text class. This leads to the following question:
> >
> > Why is data stored as a UTF8 byte array rather than as a String? Storing as 
> > byte array requires conversion and associated memory allocation upon every 
> > call to setValue and getValue. I see nothing in the source code where the 
> > byte array is used directly. The only functionality I can see related to it 
> > is that if the JVM does not support UTF8 encoding then setValue will throw an 
> > exception, but I would have thought this check would have been better placed 
> > in some initialising code so it is only run once per JVM session.
> >
> >
> > Could this be changed in XOM or is there some reason I have overlooked why it 
> > is done the way it is?
> >
> >
> > Regards
> >
> >
> > Michael Whapples
> >
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