net.sf.saxon.expr.instruct

Class ComputedElement

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

net.sf.saxon.expr.instruct.ComputedElement

All Implemented Interfaces:

InstructionWithComplexContent, TailCallReturner, ValidatingInstruction, IdentityComparable

public class ComputedElement
extends ElementCreator

An instruction representing an xsl:element element in an XSLT stylesheet, or a computed element constructor in XQuery. (In both cases, if the element name is expressed as a compile-time expression, then a FixedElement instruction is used instead.)

See Also:

FixedElement

Field Summary

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

inheritNamespacesFromParent, inheritNamespacesToChildren

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

contentOp, preservingTypes

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

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

Constructor Summary

Constructors

Constructor and Description
ComputedElement(Expression elementName, Expression namespace, SchemaType schemaType, int validation, boolean inheritNamespaces, boolean allowQName) Create an instruction that creates a new element node

Method Summary

Methods

Modifier and Type	Method and Description
void	checkPermittedContents(SchemaType parentType, boolean whole) Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.
Expression	copy() Copy an expression.
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
NodeName	getElementName(XPathContext context, NodeInfo copiedNode) Callback from the superclass ElementCreator to get the nameCode for the element name
ExpressionCompiler	getExpressionCompiler() Return the compiler of the ComputedElement expression
int	getInstructionNameCode() Get the name of this instruction for diagnostic and tracing purposes
ItemType	getItemType() Get the item type of the value returned by this instruction
Expression	getNameExp() Get the expression used to compute the element name
Expression	getNamespaceExp() Get the expression used to compute the namespace URI
NamespaceResolver	getNamespaceResolver() Get the namespace resolver that provides the namespace bindings defined in the static context
String	getNewBaseURI(XPathContext context, NodeInfo copiedNode) Get the base URI for the element being constructed
boolean	isAllowNameAsQName() Ask whether the name can be supplied as a QName.
Iterable<Operand>	operands() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
void	outputNamespaceNodes(XPathContext context, Receiver out, NodeName nameCode, NodeInfo copiedNode) Callback to output namespace nodes for the new element.
protected void	promoteChildren(PromotionOffer offer) Offer promotion for subexpressions.
protected void	setNameExp(Expression elementName)
protected void	setNamespaceExp(Expression namespace)
Expression	simplify() Simplify an expression.
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform type checking of an expression and its subexpressions.

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

checkContentSequence, computeSpecialProperties, evaluateItem, exportValidationAndType, getActiveNamespaces, getCardinality, getImplementationMethod, getInheritanceFlags, getStreamingAdjunct, isInheritNamespacesFromParent, isInheritNamespacesToChildren, iterateEvents, iterateEvents, processLeavingTail, processLeavingTail, setInheritanceFlags, setInheritNamespacesFromParent, setInheritNamespacesToChildren, suppressValidation

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

addToPathMap, computeCardinality, createsNewNodes, getContentExpression, getContentOperand, getSchemaType, getValidationAction, getValidationOptions, isLazyConstruction, isPreservingTypes, optimize, setBaseURI, setContentExpression, setLazyConstruction, setNoNeedToStrip, setValidationAction

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

assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getConstructType, getExpressionName, getInstructionName, getNetCost, getSourceLocator, isXSLT, iterate, main, process, toStreamingPattern

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

adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, clearStreamabilityData, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, getConfiguration, getCost, getDependencies, getEvaluationMethod, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLocation, getObjectName, getPackageData, getParentExpression, getPosture, getPostureAndSweepIfKnown, getProperties, getProperty, getRetainedStaticContext, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStreamability, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, makeStreamingAdjunct, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, optimizeForType, promote, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setFiltered, setFlattened, setLocation, setParentExpression, setPostureAndSweep, setRetainedStaticContext, setRetainedStaticContextLocally, setStaticProperty, simplifyChildren, staticTypeCheck, toPattern, toShortString, toString, typeCheckChildren, typeError, unordered

Methods inherited from class java.lang.Object

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

Constructor Detail

ComputedElement

public ComputedElement(Expression elementName,
               Expression namespace,
               SchemaType schemaType,
               int validation,
               boolean inheritNamespaces,
               boolean allowQName)

Create an instruction that creates a new element node

Parameters:

elementName - Expression that evaluates to produce the name of the element node as a lexical QName

namespace - Expression that evaluates to produce the namespace URI of the element node. Set to null if the namespace is to be deduced from the prefix of the elementName.

schemaType - The required schema type for the content

validation - Required validation mode (e.g. STRICT, LAX, SKIP)

inheritNamespaces - true if child elements automatically inherit the namespaces of their parent

allowQName - True if the elementName expression is allowed to return a QNameValue; false if

Method Detail

getNameExp

public Expression getNameExp()

Get the expression used to compute the element name

Returns:

the expression used to compute the element name

getNamespaceExp

public Expression getNamespaceExp()

Get the expression used to compute the namespace URI

Returns:

the expression used to compute the namespace URI

setNameExp

protected void setNameExp(Expression elementName)

setNamespaceExp

protected void setNamespaceExp(Expression namespace)

operands

public Iterable<Operand> operands()

Description copied from class: Expression

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation works off the results of iterateSubExpressions()

If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

Specified by:

operands in class Instruction

Returns:

an iterator containing the sub-expressions of this expression

getNamespaceResolver

public NamespaceResolver getNamespaceResolver()

Get the namespace resolver that provides the namespace bindings defined in the static context

Returns:

the namespace resolver

simplify

public Expression simplify()
                    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

Returns:

the simplified expression (or the original if unchanged, or if modified in-situ)

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.

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)

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

getItemType

public ItemType getItemType()

Get the item type of the value returned by this instruction

Overrides:

getItemType in class ElementCreator

Returns:

the item type

promoteChildren

protected void promoteChildren(PromotionOffer offer)
                        throws XPathException

Offer promotion for subexpressions. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

Overrides:

promoteChildren in class ParentNodeConstructor

Parameters:

offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression

Throws:

XPathException - if any error is detected

checkPermittedContents

public void checkPermittedContents(SchemaType parentType,
                          boolean whole)
                            throws XPathException

Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.

Overrides:

checkPermittedContents in class Expression

Parameters:

parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type

whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content

Throws:

XPathException - if the value delivered by this expression cannot be part of the content model of the given type

getElementName

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

Callback from the superclass ElementCreator to get the nameCode for the element name

Specified by:

getElementName in class ElementCreator

Parameters:

context - The evaluation context (not used)

copiedNode - Not applicable to this overload

Returns:

the name code for the element name

Throws:

XPathException - if a failure occurs

isAllowNameAsQName

public boolean isAllowNameAsQName()

Ask whether the name can be supplied as a QName. In practice this is true for XQuery, false for XSLT

Returns:

true if the name can be supplied as a QName

getNewBaseURI

public String getNewBaseURI(XPathContext context,
                   NodeInfo copiedNode)

Description copied from class: ElementCreator

Get the base URI for the element being constructed

Specified by:

getNewBaseURI in class ElementCreator

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 void outputNamespaceNodes(XPathContext context,
                        Receiver out,
                        NodeName nameCode,
                        NodeInfo copiedNode)
                          throws XPathException

Callback to output namespace nodes for the new element.

Specified by:

outputNamespaceNodes in class ElementCreator

Parameters:

context - The execution context

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

nameCode - The name of the element node being output

copiedNode - Where this is a copied node, the node being copied

Throws:

XPathException

getInstructionNameCode

public int getInstructionNameCode()

Get the name of this instruction for diagnostic and tracing purposes

Overrides:

getInstructionNameCode in class Instruction

Returns:

a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the ComputedElement expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler

export

public void export(ExpressionPresenter out)

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

export in class Expression

Parameters:

out - the expression presenter used to display the structure