Controlling Parsing of Source Documents
Saxon does not include its own XML parser. By default:
-
On the Java platform, the default SAX parser provided as part of the JDK is used. With the Sun/Oracle JDK, this is a variant of the Apache Xerces parser customized by Sun.
-
On the .NET platform, Saxon includes a copy of the Apache Xerces parser cross-compiled to run on .NET.
An error reported by the XML parser is generally fatal. It is not possible to process ill-formed XML.
There are several ways you can cause a different XML parser to be used:
-
The
-x
and-y
options on the command line can be used to specify the class name of a SAX parser, which Saxon will load in preference to the default SAX parser. The-x
option is used for source XML documents, the-y
option for schemas and stylesheets. The equivalent options can be set programmatically or by using the configuration file. -
By default Saxon uses the
SAXParserFactory
mechanism to load a parser. This can be configured by setting the system propertyjavax.xml.parsers.SAXParserFactory
, by means of the filelib/jaxp.properties
in the JRE directory, or by adding another parser to thelib/endorsed
directory. -
The source for parsing can be supplied in the form of a
SAXSource
object, which has anXMLReader
property containing the parser instance to be used. -
On .NET, the configuration option
PREFER_JAXP_PARSER
can be set to false, in which case Saxon will use the Microsoft XML parser instead of the Apache parser. (This parser is not used by default because it does not notifyID
attributes to the application, which means the XPathid()
andidref()
functions do not work.)
Saxonica recommends use of the Xerces parser from Apache in preference to the version bundled in the JDK, which is known to have some serious bugs.
By default, Saxon invokes the parser in non-validating mode (that is, without requested DTD
validation). Note however, that the parser still needs to read the DTD if one is present,
because it may contain entity definitions that need to be expanded. DTD validation can be
requested using -dtd:on
on the command line, or equivalent API or configuration
options.
Saxon is issued with local copies of commonly-used W3C DTDs such as the XHTML, SVG, and
MathML DTDs. When Saxon itself instantiates the XML parser, it will use an
EntityResolver
that causes these local copies of DTDs to be used rather than
fetching public copies from the web (the W3C servers are increasingly failing to serve these
requests as the volume of traffic is too high). It is possible to override this using the
configuration setting ENTITY_RESOLVER_CLASS
, which can be set to the name of a
user-supplied EntityResolver
, or to the empty string to indicate that no
EntityResolver
should be used. Saxon will not add this
EntityResolver
in cases where the XML parser instance is supplied by the caller
as part of a SAXSource
object. It will add it to a parser obtained as an instance
of the class specified using the -x
and -y
command line options,
unless either the use of the EntityResolver
is suppressed using the
ENTITY_RESOLVER_CLASS
configuration option, or the instantiated parser already
has an EntityResolver
registered.
Saxon never asks the XML parser to perform schema validation. If schema validation is
required it should be requested using the command line options -val:strict
or
-val:lax
, or their API equivalents. Saxon will then use its own schema
processor to validate the document as it emerges from the XML parser. Schema processing is
done in parallel with parsing, by use of a SAX-like pipeline.