Re: null pointer exception in Saxon

Subject: Re: null pointer exception in Saxon
From: "Dave Carlson" <dcarlson@xxxxxxxxxxxxxx>
Date: Mon, 5 Jun 2000 08:20:27 -0600
Thanks for the additional investigation.  I realize that use of Hashtables
to store state information are opposed to the stateless nature of XSLT.  I'm
looking for a way to avoid their use in my stylesheet.

I'm writing an XSLT transformation that takes an XMI represenation of a UML
model as input, and produces a DTD for the corresponding document type.  I'm
about 60% there, but am working out the approach for "copy-down inheritance"
of superclass properties, and was using a hashtable to store prior entity
declarations.  I plan to announce availability of this stylesheet when I get
closer to a complete implementation.


----- Original Message -----
From: Kay Michael <Michael.Kay@xxxxxxx>
To: <xsl-list@xxxxxxxxxxxxxxxx>
Sent: Monday, June 05, 2000 5:01 AM
Subject: RE: null pointer exception in Saxon

> I'm using the extension functions in Saxon to integrate a
> Java Hashtable into a stylesheet, but get a null point exception when
> testing a null value.

In investigating this, I've found other problems in using the Java Hashtable
class from a Saxon stylesheet. The methods put() and get() take arbitrary
Objects as their values, so Saxon doesn't do the type conversion you might
expect. This has odd effects, for example after
<xsl:value-of select="hashtable:put($table, 'Mike', 'Kay')"/>
<xsl:value-of select="hashtable:put($table, 'Mike', 'King')"/>
you will have two entries in the table, because the two keys are not
considered equal.

The moral is, stick to simple data type mappings! To use the Hashtable
class, you probably need to put a wrapper around it. I'm trying to improve
the mapping rules for the next version.

Mike K

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