net.sf.saxon.expr.instruct

Class ComputedAttribute

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

net.sf.saxon.expr.instruct.SimpleNodeConstructor

net.sf.saxon.expr.instruct.AttributeCreator

net.sf.saxon.expr.instruct.ComputedAttribute

All Implemented Interfaces:

TailCallReturner, ValidatingInstruction, IdentityComparable

public final class ComputedAttribute
extends AttributeCreator

An instruction derived from an xsl:attribute element in stylesheet, or from an attribute constructor in XQuery, in cases where the attribute name is not known statically

Field Summary

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

selectOp

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
ComputedAttribute(Expression attributeName, Expression namespace, NamespaceResolver nsContext, int validationAction, SimpleType schemaType, boolean allowNameAsQName) Construct an Attribute instruction

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.
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Expression	copy() Copy an expression.
Item	evaluateItem(XPathContext context) Evaluate as an expression.
NodeName	evaluateNodeName(XPathContext context) Determine the name to be used for the attribute, as an integer name code
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
int	getCardinality() Get the static cardinality of this expression
ExpressionCompiler	getExpressionCompiler() Return the compiler of the ComputedAttribute expression
int	getInstructionNameCode() Get the name of this instruction
ItemType	getItemType() Get the static type of this expression
Expression	getNameExp() Get the expression used to compute the name of the attribute
Expression	getNamespaceExp() Get the expression used to compute the namespace part of the name of the attribute
NamespaceResolver	getNamespaceResolver() Get the namespace resolver used to resolve any prefix in the name of the attribute
boolean	isAllowNameAsQName() Ask whether it is allowed for the name to be evaluted as an xs:QName instance (true in XQuery)
void	localTypeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Method to perform type-checking specific to the kind of instruction
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.
protected void	promoteChildren(PromotionOffer offer) Offer promotion for subexpressions.
void	setNameExp(Expression attributeName)
void	setNamespace(Expression namespace)
void	setRejectDuplicates() Indicate that two attributes with the same name are not acceptable.

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

getOptions, getSchemaType, getValidationAction, processValue, setNoSpecialChars, setOptions, setSchemaType, setValidationAction, validateOrphanAttribute

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

checkContent, computeCardinality, createsNewNodes, getSelect, getStreamingAdjunct, iterate, processLeavingTail, setSelect, typeCheck

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

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

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

addToPathMap, 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, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, optimizeForType, promote, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setFiltered, setFlattened, setLocation, setParentExpression, setPostureAndSweep, setRetainedStaticContext, setRetainedStaticContextLocally, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, 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

ComputedAttribute

public ComputedAttribute(Expression attributeName,
                 Expression namespace,
                 NamespaceResolver nsContext,
                 int validationAction,
                 SimpleType schemaType,
                 boolean allowNameAsQName)

Construct an Attribute instruction

Parameters:

attributeName - An expression to calculate the attribute name

namespace - An expression to calculate the attribute namespace

nsContext - a NamespaceContext object containing the static namespace context of the stylesheet instruction

validationAction - e.g. validation=strict, lax, strip, preserve

schemaType - Type against which the attribute must be validated. This must not be a namespace-sensitive type; it is the caller's responsibility to check this.

allowNameAsQName - true if the attributeName expression is allowed to evaluate to a value of type xs:QName (true in XQuery, false in XSLT)

Method Detail

setRejectDuplicates

public void setRejectDuplicates()

Indicate that two attributes with the same name are not acceptable. (This option is set in XQuery, but not in XSLT)

Overrides:

setRejectDuplicates in class AttributeCreator

getInstructionNameCode

public int getInstructionNameCode()

Get the name of this instruction

Overrides:

getInstructionNameCode in class Instruction

Returns:

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

getNameExp

public Expression getNameExp()

Get the expression used to compute the name of the attribute

Returns:

the expression used to compute the name of the attribute

getNamespaceExp

public Expression getNamespaceExp()

Get the expression used to compute the namespace part of the name of the attribute

Returns:

the expression used to compute the namespace part of the name of the attribute

setNameExp

public void setNameExp(Expression attributeName)

setNamespace

public void setNamespace(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.

Overrides:

operands in class SimpleNodeConstructor

Returns:

an iterator containing the sub-expressions of this expression

getNamespaceResolver

public NamespaceResolver getNamespaceResolver()

Get the namespace resolver used to resolve any prefix in the name of the attribute

Returns:

the namespace resolver if one has been saved; or null otherwise

getItemType

public ItemType getItemType()

Get the static type of this expression

Overrides:

getItemType in class AttributeCreator

Returns:

the static type of the item returned by this expression

getCardinality

public int getCardinality()

Get the static cardinality of this expression

Overrides:

getCardinality in class Expression

Returns:

the static cardinality (exactly one)

isAllowNameAsQName

public boolean isAllowNameAsQName()

Ask whether it is allowed for the name to be evaluted as an xs:QName instance (true in XQuery)

Returns:

the boolean if name is allowed as a QName

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 AttributeCreator

Returns:

a set of flags indicating static properties of this expression

localTypeCheck

public void localTypeCheck(ExpressionVisitor visitor,
                  ContextItemStaticInfo contextItemType)
                    throws XPathException

Description copied from class: SimpleNodeConstructor

Method to perform type-checking specific to the kind of instruction

Specified by:

localTypeCheck in class SimpleNodeConstructor

Parameters:

visitor - an expression visitor

contextItemType - the static type of the context item

Throws:

XPathException - if a type error is detected

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 SimpleNodeConstructor

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)

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

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 SimpleNodeConstructor

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

evaluateNodeName

public NodeName evaluateNodeName(XPathContext context)
                          throws XPathException

Determine the name to be used for the attribute, as an integer name code

Overrides:

evaluateNodeName in class SimpleNodeConstructor

Parameters:

context - Dynamic evaluation context

Returns:

the integer name code for the attribute name

Throws:

XPathException

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Description copied from class: SimpleNodeConstructor

Evaluate as an expression.

Overrides:

evaluateItem in class SimpleNodeConstructor

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

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the ComputedAttribute 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