Package net.sf.saxon.instruct
Class SimpleNodeConstructor
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.instruct.Instruction
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- net.sf.saxon.instruct.SimpleNodeConstructor
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,EvaluableItem
,SequenceIterable
,TailCallReturner
,InstructionInfo
,org.xml.sax.Locator
- Direct Known Subclasses:
AttributeCreator
,Comment
,Namespace
,ProcessingInstruction
,ValueOf
public abstract class SimpleNodeConstructor extends Instruction
Common superclass for XSLT instructions whose content template produces a text value: xsl:attribute, xsl:comment, xsl:processing-instruction, xsl:namespace, and xsl:text, and their XQuery equivalents- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description protected Expression
select
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Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Constructor Summary
Constructors Constructor Description SimpleNodeConstructor()
Default constructor used by subclasses
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description protected java.lang.String
checkContent(java.lang.String data, XPathContext context)
Check the content of the node, and adjust it if necessary.int
computeCardinality()
Get the cardinality of the sequence returned by evaluating this instructionint
computeSpecialProperties()
Get the static properties of this expression (other than its type).boolean
createsNewNodes()
Determine whether this instruction creates new nodes.Item
evaluateItem(XPathContext context)
Evaluate as an expression.int
evaluateNameCode(XPathContext context)
Run-time method to compute the name of the node being constructed.java.lang.CharSequence
expandChildren(XPathContext context)
Expand the stylesheet elements subordinate to this one, returning the result as a string.Expression
getSelect()
Get the expression that determines the string value of the constructed nodeSequenceIterator
iterate(XPathContext context)
Return an Iterator to iterate over the values of a sequence.java.util.Iterator
iterateSubExpressions()
Get the immediate sub-expressions of this expression.abstract void
localTypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Method to perform type-checking specific to the kind of instructionExpression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.protected void
promoteInst(PromotionOffer offer)
Offer promotion for subexpressions.boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionvoid
setSelect(Expression select, Configuration config)
Set the select expression: the value of this expression determines the string-value of the nodeExpression
simplify(ExpressionVisitor visitor)
Simplify an expression.Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
The typeCheck() method is called in XQuery, where node constructors are implemented as Expressions.-
Methods inherited from class net.sf.saxon.instruct.Instruction
assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getConstructType, getImplementationMethod, getInstructionNameCode, getItemType, getSourceLocator, isXSLT, process, processLeavingTail, promote
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError
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Field Detail
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select
protected Expression select
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Method Detail
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setSelect
public void setSelect(Expression select, Configuration config) throws XPathException
Set the select expression: the value of this expression determines the string-value of the node- Parameters:
select
- the expression that computes the string value of the nodeconfig
- the Saxon configuration (used for example to do early validation of the content of an attribute against the schema-defined type)- Throws:
XPathException
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getSelect
public Expression getSelect()
Get the expression that determines the string value of the constructed node- Returns:
- the select expression
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createsNewNodes
public final boolean createsNewNodes()
Determine whether this instruction creates new nodes. This implementation returns true.- Overrides:
createsNewNodes
in classInstruction
- Returns:
- true if the instruction creates new nodes (or if it can't be proved that it doesn't)
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computeCardinality
public int computeCardinality()
Get the cardinality of the sequence returned by evaluating this instruction- Overrides:
computeCardinality
in classInstruction
- Returns:
- the static cardinality
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simplify
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Description copied from class:Instruction
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.- Specified by:
simplify
in classInstruction
- Parameters:
visitor
- an expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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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 classInstruction
- Returns:
- a set of flags indicating static properties of this expression
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localTypeCheck
public abstract void localTypeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
Method to perform type-checking specific to the kind of instruction- Parameters:
visitor
- an expression visitorcontextItemType
- the static type of the context item- Throws:
XPathException
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
The typeCheck() method is called in XQuery, where node constructors are implemented as Expressions. In this case the required type for the select expression is a single string.- Overrides:
typeCheck
in classExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the rewritten expression
- Throws:
XPathException
- if any static errors are found in this expression or any of its children
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optimize
public Expression optimize(ExpressionVisitor visitor, ItemType 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 classExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 toType.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)
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iterateSubExpressions
public java.util.Iterator iterateSubExpressions()
Description copied from class:Expression
Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.- Overrides:
iterateSubExpressions
in classExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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replaceSubExpression
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression- Overrides:
replaceSubExpression
in classExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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expandChildren
public java.lang.CharSequence expandChildren(XPathContext context) throws XPathException
Expand the stylesheet elements subordinate to this one, returning the result as a string. The expansion must not generate any element or attribute nodes.- Parameters:
context
- The dynamic context for the transformation- Returns:
- the value that will be used as the string value of the constructed node
- Throws:
XPathException
- if any error occurs
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evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate as an expression. We rely on the fact that when these instructions are generated by XQuery, there will always be a valueExpression to evaluate the content- Specified by:
evaluateItem
in interfaceEvaluableItem
- Overrides:
evaluateItem
in classInstruction
- 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
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checkContent
protected java.lang.String checkContent(java.lang.String data, XPathContext context) throws XPathException
Check the content of the node, and adjust it if necessary. The checks depend on the node kind.- Parameters:
data
- the supplied contentcontext
- the dynamic context- Returns:
- the original content, unless adjustments are needed
- Throws:
XPathException
- if the content is invalid
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evaluateNameCode
public int evaluateNameCode(XPathContext context) throws XPathException
Run-time method to compute the name of the node being constructed. This is overridden for nodes that have a name. The default implementation returns -1, which is suitable for unnamed nodes such as comments- Parameters:
context
- the XPath dynamic evaluation context- Returns:
- the name pool nameCode identifying the name of the constructed node
- Throws:
XPathException
- if any failure occurs
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
Description copied from class:Instruction
Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.- Specified by:
iterate
in interfaceSequenceIterable
- Overrides:
iterate
in classInstruction
- Parameters:
context
- supplies the context for evaluation- Returns:
- a SequenceIterator that can be used to iterate over the result of the expression
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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promoteInst
protected void promoteInst(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:
promoteInst
in classInstruction
- 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
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