net.sf.saxon.expr.instruct

Class ElementCreator

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

net.sf.saxon.expr.instruct.ParentNodeConstructor

net.sf.saxon.expr.instruct.ElementCreator

All Implemented Interfaces:

SourceLocator, TailCallReturner, ValidatingInstruction, IdentityComparable, InstructionInfo

Direct Known Subclasses:

ComputedElement, Copy, FixedElement

public abstract class ElementCreator
extends ParentNodeConstructor

An instruction that creates an element node. There are two subtypes, FixedElement for use where the name is known statically, and Element where it is computed dynamically. To allow use in both XSLT and XQuery, the class acts both as an Instruction and as an Expression.

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	inheritNamespacesFromParent The inheritNamespacesFromParent flag indicates that this element should inherit the namespaces of its parent element in the result tree.
protected boolean	inheritNamespacesToChildren The inheritNamespacesToChildren flag indicates that the namespace nodes on the element created by this instruction are to be inherited (copied) on the children of this element.
protected Expression	onEmpty The onEmpty expression is used in XSLT 3.0 to supply an alternative result to be returned when the content of the element (including attributes) is empty.

Fields inherited from class net.sf.saxon.expr.instruct.ParentNodeConstructor

content, preservingTypes

Fields inherited from class net.sf.saxon.expr.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
ElementCreator() Construct an ElementCreator.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	checkContentSequence(StaticContext env) Check statically whether the content of the element creates attributes or namespaces after creating any child nodes
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Item	evaluateItem(XPathContext context) Evaluate the constructor, returning the constructed element node.
NamespaceBinding[]	getActiveNamespaces() Callback to get a list of the intrinsic namespaces that need to be generated for the element.
int	getCardinality() Determine the static cardinality of the expression.
abstract NodeName	getElementName(XPathContext context, NodeInfo copiedNode) Determine (at run-time) the name code of the element being constructed
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType() Get the item type of the value returned by this instruction
abstract String	getNewBaseURI(XPathContext context, NodeInfo copiedNode) Get the base URI for the element being constructed
Expression	getOnEmpty() Get the on-empty expression, which defines the value to be returned if the element would otherwise be empty
StreamingAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
boolean	isInheritNamespacesFromParent() Determine whether this element inherits namespaces from its parent.
boolean	isInheritNamespacesToChildren() Determine whether the inherit namespaces flag is set
EventIterator	iterateEvents(XPathContext context) Deliver the result of the expression as a sequence of events.
protected EventIterator	iterateEvents(XPathContext context, NodeInfo copiedNode)
Iterable<Operand>	operands() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.
abstract void	outputNamespaceNodes(XPathContext context, Receiver receiver, NodeName nameCode, NodeInfo copiedNode) Callback to output namespace nodes for the new element.
TailCall	processLeavingTail(XPathContext context) Evaluate the instruction to produce a new element node.
TailCall	processLeavingTail(XPathContext context, NodeInfo copiedNode) Evaluate the instruction to produce a new element node.
boolean	replaceOperand(Expression original, Expression replacement) Replace one subexpression by a replacement subexpression
void	setOnEmpty(Expression onEmpty) Set the on-empty expression, which defines the value to be returned if the element would otherwise be empty
Expression	simplify(ExpressionVisitor visitor) Simplify an expression.
void	suppressValidation(int parentValidationMode) Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation.
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.expr.instruct.ParentNodeConstructor

addToPathMap, computeCardinality, createsNewNodes, getBaseURI, getContentExpression, getSchemaType, getValidationAction, getValidationOptions, isLazyConstruction, isPreservingTypes, promoteInst, setBaseURI, setContentExpression, setLazyConstruction, setNoNeedToStrip, setValidationAction

Methods inherited from class net.sf.saxon.expr.instruct.Instruction

assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getConstructType, getExpressionName, getInstructionName, getInstructionNameCode, getIteratorFromProcessMethod, getSourceLocator, isXSLT, iterate, process, promote, toStreamingPattern

Methods inherited from class net.sf.saxon.expr.Expression

adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeStaticProperties, copy, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, explain, getColumnNumber, getConfiguration, getContainer, getDependencies, getEvaluationMethod, getExpressionCompiler, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLocationId, getObjectName, getPosture, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamability, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, makeStreamingAdjunct, markTailFunctionCalls, operandList, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, setPostureAndSweep, staticTypeCheck, toPattern, toShortString, toString, typeError, unordered

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface javax.xml.transform.SourceLocator

getColumnNumber, getLineNumber, getPublicId, getSystemId

Field Detail

inheritNamespacesToChildren

protected boolean inheritNamespacesToChildren

The inheritNamespacesToChildren flag indicates that the namespace nodes on the element created by this instruction are to be inherited (copied) on the children of this element. That is, if this flag is false, the child elements must carry a namespace undeclaration for all the namespaces on the parent, unless they are redeclared in some way.

inheritNamespacesFromParent

protected boolean inheritNamespacesFromParent

The inheritNamespacesFromParent flag indicates that this element should inherit the namespaces of its parent element in the result tree. That is, if this flag is false, this element must carry a namespace undeclaration for all the namespaces on its parent, unless they are redeclared in some way.

onEmpty

protected Expression onEmpty

The onEmpty expression is used in XSLT 3.0 to supply an alternative result to be returned when the content of the element (including attributes) is empty. The most common case is to return an empty sequence instead of constructing the element.

Constructor Detail

ElementCreator

public ElementCreator()

Construct an ElementCreator. Exists for the benefit of subclasses.

Method Detail

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException

Description copied from class: Expression

Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation simplifies its operands.

Overrides:

simplify in class Expression

Parameters:

visitor - an expression visitor

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                   ContextItemStaticInfo contextInfo)
                     throws XPathException

Description copied from class: Expression

Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

If the implementation returns a value other than "this", then it is required to ensure that the location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

Overrides:

typeCheck in class ParentNodeConstructor

Parameters:

visitor - an expression visitor

contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

optimize

public Expression optimize(ExpressionVisitor visitor,
                  ContextItemStaticInfo contextItemType)
                    throws XPathException

Description copied from class: Expression

Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Overrides:

optimize in class ParentNodeConstructor

Parameters:

visitor - an expression visitor

contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE

Returns:

the original expression, rewritten if appropriate to optimize execution

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

getItemType

public ItemType getItemType()

Get the item type of the value returned by this instruction

Overrides:

getItemType in class Instruction

Returns:

the item type

getCardinality

public int getCardinality()

Description copied from class: Expression

Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.

Overrides:

getCardinality in class ParentNodeConstructor

Returns:

one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

operands

public Iterable<Operand> operands()

Description copied from class: ParentNodeConstructor

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

Overrides:

operands in class ParentNodeConstructor

Returns:

an iterator containing the sub-expressions of this expression

replaceOperand

public boolean replaceOperand(Expression original,
                     Expression replacement)

Replace one subexpression by a replacement subexpression

Overrides:

replaceOperand in class ParentNodeConstructor

Parameters:

original - the original subexpression

replacement - the replacement subexpression

Returns:

true if the original subexpression is found

isInheritNamespacesToChildren

public boolean isInheritNamespacesToChildren()

Determine whether the inherit namespaces flag is set

Returns:

true if namespaces constructed on this parent element are to be inherited by its children

isInheritNamespacesFromParent

public boolean isInheritNamespacesFromParent()

Determine whether this element inherits namespaces from its parent. True except in XQuery where one direct element constructor forms the immediate content of another (see W3C bug 22334)

Returns:

true if this child element inherits namespaces from its parent element

setOnEmpty

public void setOnEmpty(Expression onEmpty)

Set the on-empty expression, which defines the value to be returned if the element would otherwise be empty

Parameters:

onEmpty - the expression to be evaluated if the element would otherwise be empty

getOnEmpty

public Expression getOnEmpty()

Get the on-empty expression, which defines the value to be returned if the element would otherwise be empty

Returns:

the on-empty expression if there is one, or null otherwise

computeSpecialProperties

public int computeSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

Overrides:

computeSpecialProperties in class Instruction

Returns:

a set of flags indicating static properties of this expression

suppressValidation

public void suppressValidation(int parentValidationMode)

Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation. The default implementation does nothing.

Overrides:

suppressValidation in class Expression

Parameters:

parentValidationMode - the kind of validation being performed on the parent expression

checkContentSequence

protected void checkContentSequence(StaticContext env)
                             throws XPathException

Check statically whether the content of the element creates attributes or namespaces after creating any child nodes

Specified by:

checkContentSequence in class ParentNodeConstructor

Parameters:

env - the static context

Throws:

XPathException

getElementName

public abstract NodeName getElementName(XPathContext context,
                      NodeInfo copiedNode)
                                 throws XPathException

Determine (at run-time) the name code of the element being constructed

Parameters:

context - the XPath dynamic evaluation context

copiedNode - for the benefit of xsl:copy, the node being copied; otherwise null

Returns:

the integer name code representing the element name

Throws:

XPathException - if a failure occurs

getNewBaseURI

public abstract String getNewBaseURI(XPathContext context,
                   NodeInfo copiedNode)

Get the base URI for the element being constructed

Parameters:

context - the XPath dynamic evaluation context

copiedNode - the node being copied (for xsl:copy), otherwise null

Returns:

the base URI of the constructed element

outputNamespaceNodes

public abstract void outputNamespaceNodes(XPathContext context,
                        Receiver receiver,
                        NodeName nameCode,
                        NodeInfo copiedNode)
                                   throws XPathException

Callback to output namespace nodes for the new element. This method is responsible for ensuring that a namespace node is always generated for the namespace of the element name itself.

Parameters:

context - The execution context

receiver - the Receiver where the namespace nodes are to be written

nameCode - the name code of the element being created

copiedNode - the node being copied (for xsl:copy) or null otherwise

Throws:

XPathException - if a dynamic error occurs

getActiveNamespaces

public NamespaceBinding[] getActiveNamespaces()
                                       throws XPathException

Callback to get a list of the intrinsic namespaces that need to be generated for the element.

Returns:

the set of namespace bindings.

Throws:

XPathException - if an error occurs

getImplementationMethod

public int getImplementationMethod()

An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is prefered. For instructions this is the process() method.

Overrides:

getImplementationMethod in class Instruction

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

iterateEvents

public EventIterator iterateEvents(XPathContext context)
                            throws XPathException

Description copied from class: Expression

Deliver the result of the expression as a sequence of events.

The events (of class PullEvent) are either complete items, or one of startElement, endElement, startDocument, or endDocument, known as semi-nodes. The stream of events may also include a nested EventIterator. If a start-end pair exists in the sequence, then the events between this pair represent the content of the document or element. The content sequence will have been processed to the extent that any attribute and namespace nodes in the content sequence will have been merged into the startElement event. Namespace fixup will have been performed: that is, unique prefixes will have been allocated to element and attribute nodes, and all namespaces will be declared by means of a namespace node in the startElement event or in an outer startElement forming part of the sequence. However, duplicate namespaces may appear in the sequence.

The content of an element or document may include adjacent or zero-length text nodes, atomic values, and nodes represented as nodes rather than broken down into events.

Overrides:

iterateEvents in class Expression

Parameters:

context - The dynamic evaluation context

Returns:

the result of the expression as an iterator over a sequence of PullEvent objects

Throws:

XPathException - if a dynamic error occurs during expression evaluation

iterateEvents

protected EventIterator iterateEvents(XPathContext context,
                          NodeInfo copiedNode)
                               throws XPathException

Throws:

XPathException

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws XPathException

Evaluate the instruction to produce a new element node. This method is typically used when there is a parent element or document in a result tree, to which the new element is added.

Specified by:

processLeavingTail in interface TailCallReturner

Specified by:

processLeavingTail in class Instruction

Parameters:

context - XPath dynamic evaluation context

Returns:

null (this instruction never returns a tail call)

Throws:

XPathException

processLeavingTail

public final TailCall processLeavingTail(XPathContext context,
                          NodeInfo copiedNode)
                                  throws XPathException

Evaluate the instruction to produce a new element node. This method is typically used when there is a parent element or document in a result tree, to which the new element is added.

Parameters:

context - XPath dynamic evaluation context

copiedNode - null except in the case of xsl:copy, when it is the node being copied; otherwise null

Returns:

null (this instruction never returns a tail call)

Throws:

XPathException - if a dynamic error occurs

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the constructor, returning the constructed element node. If lazy construction mode is in effect, then an UnconstructedParent object is returned instead.

Overrides:

evaluateItem in class Instruction

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

Throws:

XPathException - if any dynamic error occurs evaluating the expression

getStreamingAdjunct

public StreamingAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class Expression

Returns:

the relevant StreamingAdjunct, or null if none is available