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## Package net.sf.saxon.event

This package provides classes that feed SAX-like events from one tree to another.

See:
Description

Interface Summary
LocationProvider | LocationProvider: this is a marker interface used to identify an object that provides the location of elements in a source document or instructions in a stylesheet or query.
Receiver | Receiver: This interface represents a recipient of XML tree-walking (push) events.
SaxonLocator | SaxonLocator: this interface exists to unify the SAX Locator and JAXP SourceLocator interfaces, which are identical.

Class Summary
Builder | The abstract Builder class is responsible for taking a stream of SAX events and constructing a Document tree.
CDATAFilter | CDATAFilter: This ProxyEmitter converts character data to CDATA sections, if the character data belongs to one of a set of element types to be handled this way.
CharacterMapExpander | CharacterMapExpander: This ProxyEmitter expands characters occurring in a character map, as specified by the XSLT 2.0 xsl:character-map declaration
CommentStripper | The CommentStripper class is a filter that removes all comments and processing instructions.
ComplexContentOutputter | This class is used for generating complex content, that is, the content of an element or document node.
ContentHandlerProxy | A ContentHandlerProxy is an Emitter that filters data before passing it to an underlying SAX2 ContentHandler.
DocumentSender | Sends an entire document to a Receiver.
Emitter | Emitter: This abstract class defines methods that must be implemented by components that format SAXON output.
HTMLEmitter | This class generates HTML output
HTMLIndenter | HTMLIndenter: This ProxyEmitter indents HTML elements, by adding whitespace character data where appropriate.
HTMLTagHashSet | A simple class for testing membership of a fixed set of casse-insensitive ASCII strings.
LocationCopier | A Receiver that can be inserted into an event pipeline to copy location information.
MessageEmitter | MessageEmitter is the default Emitter for xsl:message output.
NamePoolConverter | This class is a filter that passes all Receiver events through unchanged, except that it changes namecodes to allow for the source and the destination using different NamePools.
NamespaceReducer | NamespaceReducer is a ProxyReceiver responsible for removing duplicate namespace declarations.
PIGrabber | The PIGrabber class is a Receiver that looks for xml-stylesheet processing instructions and tests whether they match specified criteria; for those that do, it creates an InputSource object referring to the relevant stylesheet
PipelineConfiguration | A PipelineConfiguration sets options that apply to all the operations in a pipeline.
ProxyReceiver | A ProxyReceiver is an Receiver that filters data before passing it to another underlying Receiver.
ReceiverOptions | ReceiverOptions defines a set of constants, which can be used in calls to methods on the Receiver interface.
ReceivingContentHandler | ReceivingContentHandler is a glue class that provides a standard SAX ContentHandler interface to a Saxon Receiver.
ResultWrapper | Helper class to construct a serialization pipeline for a given result destination and a given set of output properties.
SaxonOutputKeys | Provides string constants that can be used to set output properties for a Transformer, or to retrieve output properties from a Transformer or Templates object.
Sender | Sender is a helper class that sends events to a Receiver from any kind of Source object
SequenceOutputter | This outputter is used when writing a sequence of atomic values and nodes, that is, when xsl:variable is used with content and an "as" attribute.
SequenceReceiver | SequenceReceiver: this extension of the Receiver interface is used when processing a sequence constructor.
StandardOutputResolver | This class defines the default OutputURIResolver.
StartTagBuffer | StartTagBuffer is a ProxyReceiver that buffers attributes and namespace events within a start tag.
Stripper | The Stripper class maintains details of which elements need to be stripped.
TeeOutputter | TeeOutputter: a SequenceReceiver that duplicates received events to two different destinations
TEXTEmitter | This class generates TEXT output
TransformerReceiver | TransformerReceiver is similar in concept to the JAXP TransformerHandler, except that it implements Saxon's Receiver interface rather than the standard SAX2 interface.
TreeReceiver | A TreeReceiver acts as a bridge between a SequenceReceiver, which can receive events for constructing any kind of sequence, and an ordinary Receiver, which only handles events relating to the building of trees.
UncommittedEmitter | This class generates XML or HTML output depending on whether the first tag output is " "
XHTMLEmitter | XHTMLEmitter is an Emitter that generates XHTML output.
XMLEmitter | XMLEmitter is an Emitter that generates XML output to a specified destination.
XMLIndenter | XMLIndenter: This ProxyEmitter indents elements, by adding character data where appropriate.

Exception Summary
NoOpenStartTagException | Exception indicating that an attribute or namespace node has been written when there is no open element to write it to

## Package net.sf.saxon.event Description

This package provides classes that feed SAX-like events from one tree to another. Many of these classes are associated with serializing the output of a stylesheet, but there are also classes for building a tree from a stream of events, for stripping whitespace, and so on.

The `Receiver` interface defines a class that accepts a stream of events, with one method defined for each kind of event. The events are modelled on the design of SAX, but adapted to the XPath data model and to the use of Saxon's NamePool. Attributes and namespaces are notified individually after the start of the relevant element.

The immediate output of node constructors in a query or stylesheet goes to a `SequenceReceiver`. This is a subclass of `Receiver` that can handle an arbitrary sequence, containing atomic values as well as nodes. When constructing the content of an element, a `ComplexContentOutputter` is used; when constructing the content of a node such as a text node or attribute, a `SequenceOutputter` is used instead.

The final destination of the push pipeline is sometimes a serializer, and sometimes a tree builder. The final serialization classes are subclasses of `Emitter`, but some of the serialization work (such as indentation or application of character maps) is done by other classes on the pipeline. These are generally constructed by extending the `ProxyReceiver` class.

The Emitter is an abstract implementation of the Receiver interface. As well as supporting the Receiver interface, it provides methods for controlling the destination of serialized output (a Writer or OutputStream) and for setting serialization properties (in a Properties object). In practice nearly all the implementations of Receiver are currently subclasses of Emitter, but this may change in the future.

The package includes emitters for the standard output methods xml, html, and text, and proxy emitters to allow a sequence of filters to be applied to the output.

,

The class `ContentHandlerProxy` allows events to be converted into standard SAX events and sent to a SAX2 `ContentHandler`. Similarly, the class `ProxyReceiver` acts as a `ContentHandler`, accepting SAX2 events and feeding them into a `Receiver` pipeline.

The class `Builder` is a `Receiver` that constructs a tree representation of the document in memory. There are two subclasses for Saxon's two native tree models. Other classes such as a `Stripper` and a `NamespaceReducer` are used to modify the document by adding filters to the pipeline.

Saxon's schema validator is also implemented using this push pipeline model. The classes that perform schema validation, however, are part of a different package: `com.saxonica.validate`.

Michael H. Kay
Saxonica Limited
9 February 2005

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