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Massive addition of SAX documentation from Martin von Loewis

Browse source 
<loewis@informatik.hu-berlin.de>.

Reorganized to be more like other parts of the documentation in its
arrangement, but with few content changes.

This closes SourceForge patch #101850.
This commit is contained in:
Fred Drake 2000-10-12 20:05:09 +00:00
parent 110941a4ba
commit 014f0e3394
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\section{\module{xml.sax.handler} ---
Base classes for SAX handlers}
\declaremodule{standard}{xml.sax.handler}
\modulesynopsis{Base classes for SAX event handlers.}
\sectionauthor{Martin v. L\"owis}{loewis@informatik.hu-berlin.de}
\moduleauthor{Lars Marius Garshol}{larsga@garshol.priv.no}
\versionadded{2.0}
The SAX API defines four kinds of handlers: content handlers, DTD
handlers, error handlers, and entity resolvers. Applications normally
only need to implement those interfaces whose events they are
interested in; they can implement the interfaces in a single object or
in multiple objects. Handler implementations should inherit from the
base classes provided in the module \module{xml.sax}, so that all
methods get default implementations.
\begin{classdesc}{ContentHandler}{}
This is the main callback interface in SAX, and the one most
important to applications. The order of events in this interface
mirrors the order of the information in the document.
\end{classdesc}
\begin{classdesc}{DTDHandler}{}
Handle DTD events.
This interface specifies only those DTD events required for basic
parsing (unparsed entities and attributes).
\end{classdesc}
\begin{classdesc}{EntityResolver}{}
Basic interface for resolving entities. If you create an object
implementing this interface, then register the object with your
Parser, the parser will call the method in your object to resolve all
external entities.
\end{classdesc}
In addition to these classes, \module{xml.sax.handler} provides
symbolic constants for the feature and property names.
\begin{datadesc}{feature_namespaces}
Value: \code{"http://xml.org/sax/features/namespaces"}\\
true: Perform Namespace processing (default).\\
false: Optionally do not perform Namespace processing
(implies namespace-prefixes).\\
access: (parsing) read-only; (not parsing) read/write\\
\end{datadesc}
\begin{datadesc}{feature_namespace_prefixes}
Value: \code{"http://xml.org/sax/features/namespace-prefixes"}\\
true: Report the original prefixed names and attributes used for Namespace
declarations.\\
false: Do not report attributes used for Namespace declarations, and
optionally do not report original prefixed names (default).\\
access: (parsing) read-only; (not parsing) read/write
\end{datadesc}
\begin{datadesc}{feature_string_interning}
Value: \code{"http://xml.org/sax/features/string-interning"}
true: All element names, prefixes, attribute names, Namespace URIs, and
local names are interned using the built-in intern function.\\
false: Names are not necessarily interned, although they may be (default).\\
access: (parsing) read-only; (not parsing) read/write
\end{datadesc}
\begin{datadesc}{feature_validation}
Value: \code{"http://xml.org/sax/features/validation"}\\
true: Report all validation errors (implies external-general-entities and
external-parameter-entities).\\
false: Do not report validation errors.\\
access: (parsing) read-only; (not parsing) read/write
\end{datadesc}
\begin{datadesc}{feature_external_ges}
Value: \code{"http://xml.org/sax/features/external-general-entities"}\\
true: Include all external general (text) entities.\\
false: Do not include external general entities.\\
access: (parsing) read-only; (not parsing) read/write
\end{datadesc}
\begin{datadesc}{feature_external_pes}
Value: \code{"http://xml.org/sax/features/external-parameter-entities"}\\
true: Include all external parameter entities, including the external
DTD subset.\\
false: Do not include any external parameter entities, even the external
DTD subset.\\
access: (parsing) read-only; (not parsing) read/write
\end{datadesc}
\begin{datadesc}{all_features}
List of all features.
\end{datadesc}
\begin{datadesc}{property_lexical_handler}
Value: \code{"http://xml.org/sax/properties/lexical-handler"}\\
data type: xml.sax.sax2lib.LexicalHandler (not supported in Python 2)\\
description: An optional extension handler for lexical events like comments.\\
access: read/write
\end{datadesc}
\begin{datadesc}{property_declaration_handler}
Value: \code{"http://xml.org/sax/properties/declaration-handler"}\\
data type: xml.sax.sax2lib.DeclHandler (not supported in Python 2)\\
description: An optional extension handler for DTD-related events other
than notations and unparsed entities.\\
access: read/write
\end{datadesc}
\begin{datadesc}{property_dom_node}
Value: \code{"http://xml.org/sax/properties/dom-node"}\\
data type: org.w3c.dom.Node (not supported in Python 2) \\
description: When parsing, the current DOM node being visited if this is
a DOM iterator; when not parsing, the root DOM node for
iteration.\\
access: (parsing) read-only; (not parsing) read/write
\end{datadesc}
\begin{datadesc}{property_xml_string}
Value: \code{"http://xml.org/sax/properties/xml-string"}\\
data type: String\\
description: The literal string of characters that was the source for
the current event.\\
access: read-only
\end{datadesc}
\begin{datadesc}{all_properties}
List of all known property names.
\end{datadesc}
\subsection{ContentHandler Objects \label{content-handler-objects}}
Users are expected to subclass \class{ContentHandler} to support their
application. The following methods are called by the parser on the
appropriate events in the input document:
\begin{methoddesc}[ContentHandler]{setDocumentLocator}{locator}
Called by the parser to give the application a locator for locating
the origin of document events.
SAX parsers are strongly encouraged (though not absolutely required)
to supply a locator: if it does so, it must supply the locator to
the application by invoking this method before invoking any of the
other methods in the DocumentHandler interface.
The locator allows the application to determine the end position of
any document-related event, even if the parser is not reporting an
error. Typically, the application will use this information for
reporting its own errors (such as character content that does not
match an application's business rules). The information returned by
the locator is probably not sufficient for use with a search engine.
Note that the locator will return correct information only during
the invocation of the events in this interface. The application
should not attempt to use it at any other time.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{startDocument}{}
Receive notification of the beginning of a document.
The SAX parser will invoke this method only once, before any other
methods in this interface or in DTDHandler (except for
\method{setDocumentLocator()}).
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{endDocument}{}
Receive notification of the end of a document.
The SAX parser will invoke this method only once, and it will be the
last method invoked during the parse. The parser shall not invoke
this method until it has either abandoned parsing (because of an
unrecoverable error) or reached the end of input.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{startPrefixMapping}{prefix, uri}
Begin the scope of a prefix-URI Namespace mapping.
The information from this event is not necessary for normal
Namespace processing: the SAX XML reader will automatically replace
prefixes for element and attribute names when the
\code{http://xml.org/sax/features/namespaces} feature is true (the
default).
%% XXX This is not really the default, is it? MvL
There are cases, however, when applications need to use prefixes in
character data or in attribute values, where they cannot safely be
expanded automatically; the start/endPrefixMapping event supplies
the information to the application to expand prefixes in those
contexts itself, if necessary.
Note that start/endPrefixMapping events are not guaranteed to be
properly nested relative to each-other: all
\method{startPrefixMapping()} events will occur before the
corresponding startElement event, and all \method{endPrefixMapping()}
events will occur after the corresponding \method{endElement()} event,
but their order is not guaranteed.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{endPrefixMapping}{prefix}
End the scope of a prefix-URI mapping.
See \method{startPrefixMapping()} for details. This event will always
occur after the corresponding endElement event, but the order of
endPrefixMapping events is not otherwise guaranteed.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{startElement}{name, attrs}
Signals the start of an element in non-namespace mode.
The \var{name} parameter contains the raw XML 1.0 name of the
element type as a string and the \var{attrs} parameter holds an
instance of the \class{Attributes} class containing the attributes
of the element.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{endElement}{name}
Signals the end of an element in non-namespace mode.
The \var{name} parameter contains the name of the element type, just
as with the startElement event.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{startElementNS}{name, qname, attrs}
Signals the start of an element in namespace mode.
The \var{name} parameter contains the name of the element type as a
(uri, localname) tuple, the \var{qname} parameter the raw XML 1.0
name used in the source document, and the \var{attrs} parameter
holds an instance of the \class{AttributesNS} class containing the
attributes of the element.
Parsers may set the \var{qname} parameter to \code{None}, unless the
\code{http://xml.org/sax/features/namespace-prefixes} feature is
activated.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{endElementNS}{name, qname}
Signals the end of an element in namespace mode.
The \var{name} parameter contains the name of the element type, just
as with the startElementNS event, likewise the \var{qname} parameter.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{characters}{content}
Receive notification of character data.
The Parser will call this method to report each chunk of character
data. SAX parsers may return all contiguous character data in a
single chunk, or they may split it into several chunks; however, all
of the characters in any single event must come from the same
external entity so that the Locator provides useful information.
\var{content} may be a Unicode string or a byte string; the
\code{expat} reader module produces always Unicode strings.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{ignorableWhitespace}{}
Receive notification of ignorable whitespace in element content.
Validating Parsers must use this method to report each chunk
of ignorable whitespace (see the W3C XML 1.0 recommendation,
section 2.10): non-validating parsers may also use this method
if they are capable of parsing and using content models.
SAX parsers may return all contiguous whitespace in a single
chunk, or they may split it into several chunks; however, all
of the characters in any single event must come from the same
external entity, so that the Locator provides useful
information.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{processingInstruction}{target, data}
Receive notification of a processing instruction.
The Parser will invoke this method once for each processing
instruction found: note that processing instructions may occur
before or after the main document element.
A SAX parser should never report an XML declaration (XML 1.0,
section 2.8) or a text declaration (XML 1.0, section 4.3.1) using
this method.
\end{methoddesc}
\begin{methoddesc}[ContentHandler]{skippedEntity}{name}
Receive notification of a skipped entity.
The Parser will invoke this method once for each entity
skipped. Non-validating processors may skip entities if they have
not seen the declarations (because, for example, the entity was
declared in an external DTD subset). All processors may skip
external entities, depending on the values of the
\code{http://xml.org/sax/features/external-general-entities} and the
\code{http://xml.org/sax/features/external-parameter-entities}
properties.
\end{methoddesc}
\subsection{DTDHandler Objects \label{dtd-handler-objects}}
\class{DTDHandler} instances provide the following methods:
\begin{methoddesc}[DTDHandler]{notationDecl}{name, publicId, systemId}
Handle a notation declaration event.
\end{methoddesc}
\begin{methoddesc}[DTDHandler]{unparsedEntityDecl}{name, publicId,
systemId, ndata}
Handle an unparsed entity declaration event.
\end{methoddesc}
\subsection{EntityResolver Objects \label{entity-resolver-objects}}
\begin{methoddesc}[EntityResolver]{resolveEntity}{publicId, systemId}
Resolve the system identifier of an entity and return either the
system identifier to read from as a string, or an InputSource to
read from. The default implementation returns \var{systemId}.
\end{methoddesc}