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Subject: RE: DOCBOOK-APPS: curious about xerces parser and endorsed classe s


I'm not too familiar with the "Endorsed Standards" concept with Java.  (i.e.
I haven't read their documentation.)  However, I'm pretty sure that the
org.w3c.docm, org.xml.sax, org.xml.sax.ext, and org.xml.sax.helpers packages
are almost exclusively java Interfaces, not java Classes.  (You can't tell
by looking in the JAR file, both compile to .class files.  You'd have to
look at the source code or the javadoc to be sure.)  In case you're not
familiar with the difference, Interfaces are used in Java to define just a
list of methods that classes have to implement.  They're similar to .h files
in C -- all declaration, no implementation.  My guess is that the
xmlParserAPIs.jar just includes the Java Interfaces that define the W3C SAX
and DOM standards, which, as you note, are included with Java 1.4.  The
xercesImpl.jar file includes the Xerces code that implements those
interfaces.  You should definitely put xercesImpl.jar in your endorsed/
directory.  The xmlParserAPIs.jar file is probably identical to what ships
with Java 1.4, but Xerces might support more or more current standards.  So,
that Jar file may or may not be necessary, but I *highly* doubt it will
cause any problems.

And, yes, adding the Jar files to the endorsed/ directory will add their
contents to your CLASSPATH.

Jeff

-----Original Message-----
From: Robert P. J. Day [mailto:rpjday@mindspring.com]
Sent: Saturday, March 08, 2003 8:18 AM
To: docbook apps list
Subject: DOCBOOK-APPS: curious about xerces parser and endorsed classes



  since this involves parsing potentially docbook files, i 
figured i'd throw it out here.

  i'm trying to clarify how one properly installs the xerces-j
parser for use by, for instance, saxon, and i've read conflicting
explanations.

  the xerces-j distribution comes with three jar files:

  xmlParserAPIs.jar	# DOM and SAX interfaces
  xercesImpl.jar	# the implementations themselves
  xercesSamples.jar	# some sample programs using the parser

  ok, it's clear that, if you want to run some of the sample
programs, you should have xercesSamples.jar in the CLASSPATH
somewhere.  but the other two jar files have an added complication.

  sun's "endorsed standards override mechanism" allows you to
override some of the DOM- and SAX-related classes that come with
their JDK by copying the appropriate jar file(s) to the endorsed/
directory in the JDK install hierarchy.  so which of the other
two jar files should be copied there?

  the endorsed standards web page states that the current endorsed
standards include:

	org.wc3.dom
	org.xml.sax
	org.xml.sax.ext
	org.xml.sax.helpers

  most of the docs i've seen suggest setting up xercesImpl.jar
this way, since it contains some org.wc3.dom classes, right?
certainly, the online xerces tutorial at ibm's developerworks
suggests this.

  but the xmlParserAPIs.jar file contains a number of 
org.xml.sax classes as well.  should this be installed as
endorsed as well?  anyone have a definitive answer on that?

  also, showing my ignorance of class paths in java, once a
jar file is installed in endorsed/, are all of its contents
now considered to be on the classpath?

rday




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