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java.lang.Objectcom.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.QSignalEmitter
com.trolltech.qt.QtJambiObject
com.trolltech.qt.xmlpatterns.QAbstractXmlNodeModel
public abstract class QAbstractXmlNodeModel
The QAbstractXmlNodeModel class is an abstract base class for modeling non-XML data to look like XML for QXmlQuery
. The QAbstractXmlNodeModel specifies the interface that a node model must implement for that node model be accessible to the query engine for processing XQuery queries. A node model represents data as a structure that can be queried as if the data were XML.
The node model represented by a subclass of QAbstractXmlNodeModel is meant to be accessed by the QtXmlPatterns query engine. If the API seems a little strange in a few places, it is because the member functions are called by the query engine as it evaluates an XQuery. They aren't meant to be used programatically.Usage
QAbstractXmlNodeModel bridges the gap between the arbitrary structure of the non-XML data to be queried and the well-defined structure of XML data understood by QXmlQuery
.
Consider a chemistry application that reads the file chemistryData, which contains non-XML data that represents a chemical structure composed of molecules and atoms. The application will query this chemistry data with an XQuery it reads from file queryFile. We write a custom subclass of QAbstractXmlNodeModel (ChemistryNodeModel) that reads chemistryData and builds a data structure, perhaps composed of objects of our own classes molecule and atom. Clearly, this data structure is not XML. Our custom subclass will know how to traverse this non-XML structure and present it through the XPath Data Model interface.Error parsing snippet. The application first creates an instance of QXmlQuery
and calls setQuery()
to read queryFile containing the XQuery we want to run. Then it creates an instance of our custom node model class, ChemistryNodeModel, which is a subclass of QAbstractXmlNodeModel. Its constructor is called with the name pool
obtained from our QXmlQuery
, and with the chemistryFile containing the structure of molecules and atoms to be queried. The name pool
is required because our custom node model has the member function name()
, which returns the name
of any node in the model. The query
and the custom node model must use the same name pool for constructing these names
. The constructor would then read chemistryFile and build the custom node model structure.
To connect the query to the custom node model, we must bind a variable name used in the query to a node in the model. The variable can then be used in the query as a starting node. First, an index
for the desired starting node is retrieved by calling QAbstractXmlNodeModel::createIndex()
. Then the index is bound to a variable name, in this case queryRoot, by passing the name and the index to QXmlQuery::bindVariable()
. The query can then use a variable reference $queryRoot to refer to the starting node. Note that if the query
uses multiple variable references, a call to QXmlQuery::bindVariable()
is required to bind each different variable name to a node in the model.
The query is executed when the application calls one of the QXmlQuery
evaluation functions. The application uses QXmlQuery::evaluateTo(QAbstractXmlReceiver
*), because it then uses a serializer
to out the query result as XML to stdout. We could have used QXmlQuery::evaluateTo(QXmlResultItems
*) to get a list of result items, or QXmlQuery::evaluateTo(QStringList *) if the query evaluated to a sequence of xs:string values.
During query execution, the engine iterates over the node model using nextFromSimpleAxis()
to get the index
of the next node to be visited. The engine can get the name of a node by calling name()
with the node's index
. stringValue()
, baseUri()
, documentUri()
and kind()
are also called as needed with a node index
.
The example demonstrates the standard pattern for using a subclass of QAbstractXmlNodeModel in combination with QXmlQuery
to perform an XQuery.
QXmlQuery
and give it the XQuery to be run;QSimpleXmlNodeModel
;QXmlNodeModelIndex
for the node in the model where the QXmlQuery
should start the query;QXmlQuery::bindVariable()
to bind the QXmlNodeModelIndex
to $variable name;QXmlQuery
evaluation functions to run the query.QXmlQuery
to operate on non-XML data as if it were XML, implementing subclasses of QAbstractXmlNodeModel can involve a significant amount of work. The QSimpleXmlNodeModel
class is provided to simplify the implementation for many common use cases.See the example File System Example for a demonstration.
Nested Class Summary | |
---|---|
static class |
QAbstractXmlNodeModel.NodeCopySetting
Controls how nodes are copied with copyNodeTo. |
static class |
QAbstractXmlNodeModel.SimpleAxis
Four axes that each contain one node only. |
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter |
---|
QSignalEmitter.AbstractSignal, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9 |
Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
---|
com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal |
Field Summary |
---|
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
---|
currentSender |
Method Summary | |
---|---|
protected abstract java.util.List |
attributes(QXmlNodeModelIndex element)
Returns the attributes of element. |
abstract QUrl |
baseUri(QXmlNodeModelIndex ni)
Returns the base URI for the node whose index is n. |
QAbstractXmlNodeModel |
clone()
This method is reimplemented for internal reasons |
abstract QXmlNodeModelIndex.DocumentOrder |
compareOrder(QXmlNodeModelIndex ni1,
QXmlNodeModelIndex ni2)
This function returns the relative document order for the nodes indexed by ni1 and ni2. |
protected QXmlNodeModelIndex |
createIndex(long data)
Creates a node index with data as its internal data. |
protected QXmlNodeModelIndex |
createIndex(long data,
long additionalData)
Creates a QXmlNodeModelIndex containing data and additionalData. |
protected QXmlNodeModelIndex |
createIndex(QNativePointer pointer)
Creates a node index with pointer and additionalData as its internal data. |
protected QXmlNodeModelIndex |
createIndex(QNativePointer pointer,
long additionalData)
Creates a node index with pointer and additionalData as its internal data. |
abstract QUrl |
documentUri(QXmlNodeModelIndex ni)
Returns the document URI of n. |
abstract QXmlNodeModelIndex |
elementById(QXmlName NCName)
Returns the index of the element identified as id. |
abstract QXmlNodeModelIndex.NodeKind |
kind(QXmlNodeModelIndex ni)
Returns a value indicating the kind of node identified by ni. |
abstract QXmlName |
name(QXmlNodeModelIndex ni)
Returns the name of ni. |
abstract java.util.List |
namespaceBindings(QXmlNodeModelIndex n)
Returns the in-scope namespaces of n. |
protected abstract QXmlNodeModelIndex |
nextFromSimpleAxis(QAbstractXmlNodeModel.SimpleAxis axis,
QXmlNodeModelIndex origin)
When QtXmlPatterns evaluate path expressions, it emulate them through a combination of calls with QSimpleXmlNodeModel::SimpleAxis values. |
abstract java.util.List |
nodesByIdref(QXmlName NCName)
Returns the elements and/or attributes that have an IDREF value equal to idref. |
abstract QXmlNodeModelIndex |
root(QXmlNodeModelIndex n)
Returns the root node of the tree that contains the node whose index is n. |
abstract java.lang.String |
stringValue(QXmlNodeModelIndex n)
Returns the string value for node n. |
abstract java.lang.Object |
typedValue(QXmlNodeModelIndex n)
Returns the typed value for node node. |
Methods inherited from class com.trolltech.qt.QtJambiObject |
---|
dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr |
Methods inherited from class com.trolltech.qt.QSignalEmitter |
---|
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread |
Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
---|
__qt_signalInitialization |
Methods inherited from class java.lang.Object |
---|
getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Methods inherited from interface com.trolltech.qt.QtJambiInterface |
---|
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
Method Detail |
---|
protected final QXmlNodeModelIndex createIndex(long data)
protected final QXmlNodeModelIndex createIndex(long data, long additionalData)
QXmlNodeModelIndex
containing data and additionalData.
protected final QXmlNodeModelIndex createIndex(QNativePointer pointer)
What pointer and additionalData is, is not constrained.
protected final QXmlNodeModelIndex createIndex(QNativePointer pointer, long additionalData)
What pointer and additionalData is, is not constrained.
protected abstract java.util.List attributes(QXmlNodeModelIndex element)
public abstract QUrl baseUri(QXmlNodeModelIndex ni)
The base URI of a node can be extracted using the fn:base-uri() function. The base URI is typically used for resolving relative URIs that appear in the node or its children. It is conformant to just return the document URI, although that might not properly reflect the underlying data.
This function maps to the dm:base-uri accessor, which returns a base URI according to the following:
QUrl
, or a default constructed QUrl
. If a node has no base URI, as in the case where a comment has no parent, a default constructed QUrl
is returned.
public abstract QXmlNodeModelIndex.DocumentOrder compareOrder(QXmlNodeModelIndex ni1, QXmlNodeModelIndex ni2)
The caller guarantees that ni1 and ni2 are not null and that both identify nodes in this node model.
If ni1 is identical to ni2, QXmlNodeModelIndex::Is
is returned. If ni1 precedes ni2 in document order, QXmlNodeModelIndex::Precedes
is returned. If ni1 follows ni2 in document order, QXmlNodeModelIndex::Follows
is returned.
public abstract QUrl documentUri(QXmlNodeModelIndex ni)
If the node model maps to a URI in a natural way, return that URI. Otherwise, return the company or product URI. The document URI can be any URI as long as its valid and absolute.
The caller guarantees that n is not null and that it belongs to this QAbstractXmlNodeModel.
This function maps to the dm:document-uri accessor, which returns a document URI according to the following:
QUrl::isValid()
, and QUrl::isRelative()
.
public abstract QXmlNodeModelIndex elementById(QXmlName NCName)
The node index returned will be the element node whose value is of type ID and equals id, or it will be the element node that has an attribute whose typed value is of type ID and equals id. If there is no such element, a default constructed QXmlNodeModelIndex
instance is returned. The implementor guarantees that if the returned node index is not null, it identifies an element.
It is not sufficient for an attribute or element to merely be called id. Its value type must also be ID. However, the reserved name xml:id is sufficient.
In id, the namespace URI and the prefix are undefined, and the local name is the ID that should be looked up.
public abstract QXmlNodeModelIndex.NodeKind kind(QXmlNodeModelIndex ni)
public abstract QXmlName name(QXmlNodeModelIndex ni)
If a node does not have a name, e.g., comment nodes, a null QXmlName
is returned. QXmlNames must be created with the instance of QXmlQuery
that is being used for evaluating queries using this QAbstractXmlNodeModel.
This function maps to the dm:node-name() accessor.
If ni is a processing instruction, a QXmlName
is returned with the local name as the target name and the namespace URI and prefix both empty.
QXmlName
.
public abstract java.util.List namespaceBindings(QXmlNodeModelIndex n)
This function corresponds to the dm:namespace-nodes accessor.
The returned vector of namespace declarations includes namespaces of the ancestors of n.
The caller guarantees that n is an Element that belongs to this QAbstractXmlNodeModel.
protected abstract QXmlNodeModelIndex nextFromSimpleAxis(QAbstractXmlNodeModel.SimpleAxis axis, QXmlNodeModelIndex origin)
QSimpleXmlNodeModel::SimpleAxis
values. Therefore, the implementation of this function must return the node, if any, that appears on the axis emanating from the origin. If no such node is available, a default constructed QXmlNodeModelIndex
is returned.
QSimpleXmlNodeModel
eliminates the need to handle redundant corner cases by guaranteeing that it will never ask for:
QXmlNodeModelIndex MyTreeModel::nextFromSimpleAxis(SimpleAxis axis, const QXmlNodeModelIndex &origin) const { // Convert the QXmlNodeModelIndex to a value that is specific to what we represent. const MyValue value = toMyValue(ni); switch(axis) { case Parent: return toNodeIndex(value.parent()); case FirstChild: case PreviousSibling: case NextSibling: // and so on } }
public abstract java.util.List nodesByIdref(QXmlName NCName)
The implementor guarantees that the nodes identified by the returned indexes are elements or attributes.
It is not sufficient for an attribute or element to merely be called idref. It must also be of type IDREF. Elements must be typed as xs:IDREF or xs:IDREFS, or, in the case of attributes, as IDREF or IDREFS in the schema.
In idref, the namespace URI and the prefix are undefined, and the local name is the ID that should be looked up.
public abstract QXmlNodeModelIndex root(QXmlNodeModelIndex n)
If n identifies a node that is a direct child of the root, parent() would return the same QXmlNodeModelIndex
returned by this function.
public abstract java.lang.String stringValue(QXmlNodeModelIndex n)
The caller guarantees that n is not null and that it belong to this QAbstractXmlNodeModel instance.
This function maps to the dm:string-value() accessor, which the specification completely specifies. Here's a summary:
public abstract java.lang.Object typedValue(QXmlNodeModelIndex n)
The typed value is an atomic value, which an element or attribute contains.
The caller guarantees that node is either an element or an attribute. The implementor guarantees that the returned QVariant
has a value which is supported in XQuery. It cannot be an arbitrary QVariant
value. The implementor also guarantees that stringValue()
returns a lexical representation of typedValue()
(this is guaranteed by QSimpleXmlNodeModel::stringValue()).
If the return QVariant
is a default constructed variant, it signals that node has no typed value.
public QAbstractXmlNodeModel clone()
clone
in class java.lang.Object
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