I hit this crazy bit of schema design myself.
If you create one parser per schema document, you can give each one its
own caching grammar pool, and re-use them from document to document.
Of course, things are even more fun if you are parsing from multiple
threads.
It is possible to share the cached grammar pool (which is thread safe)
amongst multiple parsers (which are not thread safe).
My code is ugly, and can certainly be adjusted for your use case:
/**
* @param schemaLocation
* @param preloadGrammars
* @return a DOMParser for the specified schema
* @throws IOException
* @throws XNIException
*/
public static DOMParser domParserWithPrivateGrammarPool(final
URL schemaLocation, final List<URL> preloadGrammars) throws
XNIException, IOException {
final XMLGrammarPool grammarPool = new
XMLGrammarPoolImpl();
if (preloadGrammars!=null) {
preloadGrammarsIntoPool(grammarPool,preloadGrammars);
}
final XMLGrammarCachingConfiguration config = new
XMLGrammarCachingConfiguration(
new SymbolTable(), grammarPool);
config.setErrorHandler(new GenericXMLErrorHandler());
if (schemaLocation!=null) {
config.setFeature(JAXP_VALIDATION_FEATURE,
true);
config.setFeature(JAXP_SCHEMA_VALIDATION_FEATURE, true);
config.parseGrammar(XMLConstants.W3C_XML_SCHEMA_NS_URI,
schemaLocation.toString());
} else {
config.setFeature(JAXP_VALIDATION_FEATURE,false);
}
return new org.apache.xerces.parsers.DOMParser(config);
}
/**
* @param grammarPool
* @param preloadGrammars
*/
private static void preloadGrammarsIntoPool(final XMLGrammarPool
grammarPool, final List<URL> preloadGrammars) {
final XMLGrammarPreparser preparser=new
XMLGrammarPreparser();
preparser.registerPreparser(XMLGrammarDescription.XML_DTD, null);
preparser.registerPreparser(XMLGrammarDescription.XML_SCHEMA, null);
preparser.setGrammarPool(grammarPool);
for (final URL grammar:preloadGrammars) {
if (logger.isInfoEnabled()) {
logger.info("Preloading grammar for
"+grammar.toExternalForm());
}
try {
final InputStream inputStream = new
BufferedInputStream(grammar.openStream());
final XMLInputSource source=new
XMLInputSource(null,grammar.toURI().getPath(),null,inputStream,null);
if (grammar.getPath().endsWith(".dtd"))
{
preparser.preparseGrammar(XMLGrammarDescription.XML_DTD, source);
} else {
preparser.preparseGrammar(XMLGrammarDescription.XML_SCHEMA, source);
}
} catch (final IOException e) {
// Preloading is just for convenience
logger.warn("Error trying to preload
grammar file "+grammar.toExternalForm(), e);
} catch (final URISyntaxException e) {
// Preloading is just for convenience
logger.warn("Error trying to preload
grammar file "+grammar.toExternalForm(), e);
}
}
}
--
Bill Michell
Development Team Leader, Broadcast Platforms, BBC FM&T (Journalism).
-----Original Message-----
From: Adam Retter [mailto:[EMAIL PROTECTED]
Sent: 10 November 2008 11:23
To: j-users@xerces.apache.org
Subject: Problem validating using XMLGrammarPool with different Grammars
with no namespace
Hi Chaps,
I am having some problems with XMLGrammarPool and I would like to
confirm the cause of this.
I think that it is because I have a number of different XML documents
that use different XML Schemas, and these all use the same namespace
i.e. no namespace.
When I create a new XMLGrammarPool and validate document A with Schema 1
it works, however when I then validate document B with Schema 2 using
the same XMLGrammarPool it fails as it cant find the Schema. Both
document A and document B have no namespace defined.
e.g.
<a xsi:noNamespaceSchemaLocation="1.xsd"
xmlns:xsi="xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";>
...
</a>
<b xsi:noNamespaceSchemaLocation="2.xsd"
xmlns:xsi="xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";>
...
</b>
Our application needs to validate a number of different incoming XML
documents using their XML Schemas, a number of these documents all have
no namespace and use xsi:noNamespaceSchemaLocation="blah.xsd" to refer
to their Schemas.
I would like to use an XMLGrammarPool for caching Schemas to improve
performance of the system. I thought that by implementing my own
XMLGrammarPool I would be able to determine the uniqueness of an
XMLSchema by something other than its namespace, e.g. its location.
However this doesn't seem to be the case.
After some investigation with the debugger: at line 1373 of
XMLSchemaValidator in com.sun.org.apache.xerces.internal.impl.xs (Sun
JDK 1.6.0_06) I see this comment in reset(XMLComponentManager
componentManager) -
// store the external schema locations. they are set when reset is
called,
// so any other schemaLocation declaration for the same namespace will
be
// effectively ignored. because we choose to take first location hint
// available for a particular namespace.
My question then is how and what do I need to do to get this working? Or
if it is currently possible, then what am I doing wrong?
Thanks
Adam Retter
Landmark Information Group Ltd
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Eagle Way
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