Re: NPE in parser->getDOMImplementation() with CNI

[Andrew Haley <aph at redhat dot com>]

Mark Wielaard wrote:
> On Sun, 2009-06-21 at 16:46 +0100, Andrew Haley wrote:
>> Sam Ruby wrote:
>>> I'm trying to develop a JAXP implementation using CNI, but I get a
>>> NullPointerException when I try to get a DOMImplementation.  I've
>>> attached a small script (tested on Ubuntu 9.04) which demonstrates the
>>> problem.
>>>
>>> Any help would be appreciated.
>> Congratulations on this excellent test case.  Next time I want to tell
>> people how to do it right, I'll point them at your posting.
>>
>> However, I get
>>
>>  $ sh ~/testdomimpl.sh
>> gnu.xml.dom.DomDocumentBuilderFactory@160ecdad
>> gnu.xml.dom.DomDocumentBuilder@15ffbc45
>> gnu.xml.dom.DomImpl@15ef0ee5
>>
>> gnu.xml.dom.DomDocumentBuilderFactory@2df0bea7
>> gnu.xml.dom.DomDocumentBuilder@2de03d5f
>> gnu.xml.dom.DomImpl@2dd0bfdf
>>  $ gcj --version
>> gcj (GCC) 4.4.0 20090307 (Red Hat 4.4.0-0.23)
> 
> I get the same with that version of gcj.
> But on an older gcj installation:
> gcj (Debian 4.3.2-2) 4.3.2
> 
> gnu.xml.dom.DomDocumentBuilderFactory@6992f029
> gnu.xml.dom.DomDocumentBuilder@647a3539
> gnu.xml.dom.DomImpl@64826fa9
> 
> gnu.xml.dom.DomDocumentBuilderFactory@17d5dffb
> gnu.xml.dom.DomDocumentBuilder@12bcf52b
> java.lang.NullPointerException
>    at java.io.PrintStream.println(PrintStream.java:473)

I found the problem.

There is an implementation of jaxp in /usr/share/java/jaxp-1.3.jar and
another in /usr/lib/libgcj.so.90.  They are not the same version, and
they are not compatible.

If you link against /usr/lib/libgcj.so.90 then you must compile against
the version of jaxp in that library.

Do this:

gcjh -cp /usr/share/java/libgcj.jar -d headers \
  org.w3c.dom.DOMImplementation \
  javax.xml.parsers.DocumentBuilder \
  javax.xml.parsers.DocumentBuilderFactory

I don't think it's possible to override the version of jaxp that's in
/usr/lib/libgcj.so.90.

Andrew.