Newb question on applicability

["Hatten, Kenneth W. (Contractor)" <Ke...@usdoj.gov.INVALID>]

Folks -

I'm not a Dev and am not java informed to any great degree.  What I am looking for is a specific library and I think I need a specific version.  Details:

We are moving a VERY old application from one environment to another
On the target system, tomcat fails to start with messages about this library being missing:  org/apache/xerces/jaxp/SAXParserFactoryImpl

I search the new system and find :
/usr/share/doc/xml-commons-apis-1.4.01/README-sax, which contains these lines:
SAX 2.0.1 (sax2r2)
29-January-2002

So, I assume I need a new JAR file, version 2.0.1 which contains the missing library.  I've found these on mvnrepository:
sax-2.0.1.pom
sax-2.0.1.jar
maven-metadata.xml

But when I look inside the JAR file I do not see any references to SAXParserFactoryImpl .  It may be that it's hidden in one of the included files or it may be that I do not have a JAR that contains it at all.  It may be that I could use the latest version of the JAR file but I don't know how backward compatible Java JAR files are.

Does anyone have advice on usage of a later version or in fact, what I really need that encompasses the SAXParserFactoryImpl code .

Sorry, I was unable to find a search engine on the list that would allow me to find an answer.  So, a pointer to that if it exists would be handy as well.

Thanks for your forbearance and assistance.

Regards,

Ken Hatten
Systems Administrator