Clearly based on your response, and the fact that the Soft referenced table
also interns, i completely misunderstood (and still do) what the SymbolTable
class is used for.
I guess i'll have to take another attempt at understanding what it is being
used for.
----- Original Message -----
From: "Michael Glavassevich" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, January 09, 2008 4:16 PM
Subject: Re: Interning strategy
Hi Dave,
It's being interned for the application. Allows your SAX content handler
to
compare the names of elements, attributes, etc... using reference
comparison [1] instead of equals for better performance. There's an
alternate implementation of the SymbolTable [2] which is more sensitive to
memory usage. It allows interned strings to be garbage collected if
they're
only reachable through the SymbolTable.
Thanks.
[1] http://xerces.apache.org/xerces2-j/features.html#string-interning
[2]
http://xerces.apache.org/xerces2-j/javadocs/xerces2/org/apache/xerces/util/SoftReferenceSymbolTable.html
Michael Glavassevich
XML Parser Development
IBM Toronto Lab
E-mail: [EMAIL PROTECTED]
E-mail: [EMAIL PROTECTED]
"Dave Brosius" <[EMAIL PROTECTED]> wrote on 01/09/2008 01:01:06 AM:
Greetings, i was purusing old mailing list emails, and stumbled onto the
following email sent some time ago :)
Luckily, from a quick perusal of the code, it appears that the email
still
applies.
I have a question about the implementation of SymbolTable
As expected, it appears to me to that it does hashing to find a bucket,
then
walks the chain of pointers from the bucket to find a string that is
'equals'
Only if it doesn't exist is a new one added. All of this makes sense.
The question i have then, is why when you add an entry
public Entry(String symbol, Entry next) {
this.symbol = symbol.intern();
characters = new char[symbol.length()];
symbol.getChars(0, characters.length, characters, 0);
this.next = next;
}
does the code intern the string? Isn't the point of this class to stop
pollution of the constant pool and perm gen? (besides allowing for
alternate
hashing?)
Given that the one String that lives in the SymbolTable is returned, i
would
think intern is redundant.
thanks,
dave
----- Original Message -----
From: "Michael Glavassevich" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Sunday, July 24, 2005 11:57 AM
Subject: Re: Interning strategy
Elliotte Harold <[EMAIL PROTECTED]> wrote on 07/22/2005 09:35:02 PM:
> Suppose I turn on interning in the parser by setting the SAX property
> http://xml.org/sax/features/string-interning to true. Will Xerces
simply
> invoke the String.intern() method on the strings it creates or does it
> do something fancier like maintaining its own pool of string constants
> and reuse those?
It maintains a pool. See org.apache.xerces.util.SymbolTable, specifically
the addSymbol() methods.
> --
> Elliotte Rusty Harold [EMAIL PROTECTED]
> XML in a Nutshell 3rd Edition Just Published!
> http://www.cafeconleche.org/books/xian3/
> http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim
>
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>
Michael Glavassevich
XML Parser Development
IBM Toronto Lab
E-mail: [EMAIL PROTECTED]
E-mail: [EMAIL PROTECTED]
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