内容

• 公共函数
• 详细描述
• XQuery Sequences

QAbstractXmlReceiver Class

QAbstractXmlReceiver class provides a callback interface for transforming the output of a QXmlQuery . 更多...

头：	#include <QAbstractXmlReceiver>
qmake:	QT += xmlpatterns
Since:	Qt 4.4
继承者：	QXmlSerializer

• 所有成员列表，包括继承成员

注意： 此类的所有函数 可重入 .

公共函数

	QAbstractXmlReceiver ()
virtual	~QAbstractXmlReceiver ()
virtual void	atomicValue (const QVariant & value ) = 0
virtual void	attribute (const QXmlName & name , const QStringRef & value ) = 0
virtual void	characters (const QStringRef & value ) = 0
virtual void	comment (const QString & value ) = 0
virtual void	endDocument () = 0
virtual void	endElement () = 0
virtual void	endOfSequence () = 0
virtual void	namespaceBinding (const QXmlName & name ) = 0
virtual void	processingInstruction (const QXmlName & target , const QString & value ) = 0
virtual void	startDocument () = 0
virtual void	startElement (const QXmlName & name ) = 0
virtual void	startOfSequence () = 0

详细描述

QAbstractXmlReceiver class provides a callback interface for transforming the output of a QXmlQuery .

QAbstractXmlReceiver is an abstract base class that provides a callback interface for receiving an XQuery sequence , usually the output of an QXmlQuery , and transforming that sequence into a structure of your choosing, usually XML. Consider the example:

QXmlQuery query;
query.setQuery("doc('index.html')/html/body/p[1]");
QXmlSerializer serializer(query, myOutputDevice);
query.evaluateTo(&serializer);
					

First it constructs a query that gets the first paragraph from document index.html . Then it constructs an XML serializer 采用 query and myOutputDevice (Note the serializer 是 XML receiver , ie a subclass of QAbstractXmlReceiver ). Finally, it evaluates the query , producing an ordered sequence of calls to the serializer's callback functions. The sequence of callbacks transforms the query output to XML and writes it to myOutputDevice .

Although the example uses QXmlQuery to produce the sequence of callbacks to functions in QAbstractXmlReceiver , you can call the callback functions directly as long as your sequence of calls represents a valid XQuery sequence .

XQuery Sequences

An XQuery sequence is an ordered collection of zero, one, or many items . Each item is either an atomic value 或 node . An atomic value is a simple data value.

There are six kinds of nodes .

• Element Node represents an XML element.
• Attribute Node represents an XML attribute.
• A Document Node represents an entire XML document.
• A Text Node represents character data (element content).
• A Processing Instruction Node represents an XML processing instruction, which is used in an XML document to tell the application reading the document to perform some action. A typical example is to use a processing instruction to tell the application to use a particular XSLT stylesheet to display the document.
• And a Comment node represents an XML comment.

sequence of nodes and atomic values obeys the following rules. Note that Namespace Node refers to a special Attribute Node with name xmlns .

• 每个 node appears in the sequence before its children and their descendants appear.
• A node 's descendants appear in the sequence before any of its siblings appear.
• A Document Node represents an entire document. Zero or more Document Nodes can appear in a sequence , but they can only be top level items (i.e., a Document Node can't be a child of another node .
• Namespace Nodes immediately follow the Element Node with which they are associated.
• Attribute Nodes immediately follow the Namespace Nodes of the element with which they are associated, or...
• If there are no Namespace Nodes following an element, then the Attribute Nodes immediately follow the element.
• atomic value can only appear as a top level item , i.e., it can't appear as a child of a node .
• Processing Instruction Nodes do not have children, and their parent is either a Document Node 或 Element Node .
• Comment Nodes do not have children, and their parent is either a Document Node 或 Element Node .

sequence of nodes and atomic values is sent to an QAbstractXmlReceiver ( QXmlSerializer in the example above) as a sequence of calls to the receiver's callback functions. The mapping of callback functions to sequence items is as follows.

• startDocument () 和 endDocument () are called for each Document Node 在 sequence . endDocument () is not called until all the Document Node's children have appeared in the sequence .
• startElement () 和 endElement () are called for each Element Node . endElement () is not called until all the Element Node's children have appeared in the sequence .
• attribute () is called for each Attribute Node .
• comment () is called for each Comment Node .
• characters () is called for each Text Node .
• processingInstruction () is called for each Processing Instruction Node .
• namespaceBinding () is called for each Namespace Node .
• atomicValue () is called for each atomic value .

For a complete explanation of XQuery sequences, visit XQuery Data Model .

另请参阅 W3C XQuery 1.0 and XPath 2.0 Data Model (XDM) , QXmlSerializer ，和 QXmlResultItems .

成员函数文档编制

QAbstractXmlReceiver:: QAbstractXmlReceiver ()

Constructs an abstract xml receiver.

[virtual] QAbstractXmlReceiver:: ~QAbstractXmlReceiver ()

Destroys the xml receiver.

[pure virtual] void QAbstractXmlReceiver:: atomicValue (const QVariant & value )

This callback is called when an atomic value appears in the sequence 。 value is a simple data value . It is guaranteed to be valid .

[pure virtual] void QAbstractXmlReceiver:: attribute (const QXmlName & name , const QStringRef & value )

This callback is called when an attribute node appears in the sequence . name 是 attribute name 和 value string contains the attribute value.

[pure virtual] void QAbstractXmlReceiver:: characters (const QStringRef & value )

This callback is called when a text node appears in the sequence 。 value contains the text. Adjacent text nodes may not occur in the sequence , i.e., this callback must not be called twice in a row.

[pure virtual] void QAbstractXmlReceiver:: comment (const QString & value )

This callback is called when a comment node appears in the sequence 。 value is the comment text, which must not contain the string "--".

[pure virtual] void QAbstractXmlReceiver:: endDocument ()

This callback is called when the end of a document node appears in the sequence .

[pure virtual] void QAbstractXmlReceiver:: endElement ()

This callback is called when the end of an element node appears in the sequence .

[pure virtual] void QAbstractXmlReceiver:: endOfSequence ()

This callback is called once only, right after the sequence ends.

[pure virtual] void QAbstractXmlReceiver:: namespaceBinding (const QXmlName & name )

This callback is called when a namespace binding is in scope of an element. A namespace is defined by a URI. In the QXmlName name , the value of QXmlName::namespaceUri () is that URI. The value of QXmlName::prefix () is the prefix that the URI is bound to. The local name is insignificant and can be an arbitrary value.

[pure virtual] void QAbstractXmlReceiver:: processingInstruction (const QXmlName & target , const QString & value )

This callback is called when a processing instruction appears in the sequence . A processing instruction is used in an XML document to tell the application reading the document to perform some action. A typical example is to use a processing instruction to tell the application to use a particular XSLT stylesheet to process the document.

<?xml-stylesheet type="test/xsl" href="formatter.xsl"?>
					

target 是 name of the processing instruction. Its prefix and namespace URI must both be empty. Its local name is the target. In the above example, the name is xml-stylesheet .

value specifies the action to be taken. Note that the value must not contain the string "?>". In the above example, the value is type="test/xsl" href="formatter.xsl .

Generally, use of processing instructions should be avoided, because they are not namespace aware and in many contexts are stripped out anyway. Processing instructions can often be replaced with elements from a custom namespace.

[pure virtual] void QAbstractXmlReceiver:: startDocument ()

This callback is called when a document node appears in the sequence .

[pure virtual] void QAbstractXmlReceiver:: startElement (const QXmlName & name )

This callback is called when a new element node appears in the sequence . name is the valid name of the node element.

[pure virtual] void QAbstractXmlReceiver:: startOfSequence ()

This callback is called once only, right before the sequence begins.