Class ComputedElement
- 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.ParentNodeConstructor
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- net.sf.saxon.instruct.ElementCreator
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- net.sf.saxon.instruct.ComputedElement
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,EvaluableItem
,SequenceIterable
,TailCallReturner
,InstructionInfo
,org.xml.sax.Locator
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
, Serialized Form
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Field Summary
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Fields inherited from class net.sf.saxon.instruct.ElementCreator
inheritNamespaces, preservingTypes
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Fields inherited from class net.sf.saxon.instruct.ParentNodeConstructor
content
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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 ComputedElement(Expression elementName, Expression namespace, NamespaceResolver nsContext, SchemaType schemaType, int validation, boolean inheritNamespaces, boolean allowQName)
Create an instruction that creates a new element node
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
checkPermittedContents(SchemaType parentType, StaticContext env, 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
explain(ExpressionPresenter out)
Diagnostic print of expression structure.int
getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposesItemType
getItemType(TypeHierarchy th)
Get the item type of the value returned by this instructionint
getNameCode(XPathContext context)
Callback from the superclass ElementCreator to get the nameCode for the element nameExpression
getNameExpression()
Get the expression used to compute the element nameExpression
getNamespaceExpression()
Get the expression used to compute the namespace URINamespaceResolver
getNamespaceResolver()
Get the namespace resolver that provides the namespace bindings defined in the static contextjava.lang.String
getNewBaseURI(XPathContext context)
Get the base URI for the element being constructedjava.util.Iterator
iterateSubExpressions()
Get the immediate sub-expressions of this expression.Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.protected void
outputNamespaceNodes(XPathContext context, Receiver out)
Callback to output namespace nodes for the new element.protected void
promoteInst(PromotionOffer offer)
Offer promotion for subexpressions.boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionExpression
simplify(ExpressionVisitor visitor)
Simplify an expression.Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Perform type checking of an expression and its subexpressions.-
Methods inherited from class net.sf.saxon.instruct.ElementCreator
checkContentSequence, computeSpecialProperties, evaluateItem, getActiveNamespaces, getImplementationMethod, isInheritNamespaces, isPreservingTypes, iterateEvents, processLeavingTail, setValidationMode, suppressValidation
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Methods inherited from class net.sf.saxon.instruct.ParentNodeConstructor
addToPathMap, computeCardinality, createsNewNodes, getBaseURI, getCardinality, getContentExpression, getSchemaType, getValidationMode, isLazyConstruction, isNamespaceSensitive, setBaseURI, setContentExpression, setLazyConstruction, setSchemaType
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Methods inherited from class net.sf.saxon.instruct.Instruction
assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getConstructType, getSourceLocator, isXSLT, iterate, process, promote
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Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, findParentOf, getColumnNumber, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, toString, typeError
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Constructor Detail
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ComputedElement
public ComputedElement(Expression elementName, Expression namespace, NamespaceResolver nsContext, 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 QNamenamespace
- 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.nsContext
- Saved copy of the static namespace context for the instruction. Can be set to null if namespace is supplied. This namespace context must resolve the null prefix correctly, based on the different rules for XSLT and XQuery. //* @param defaultNamespace Default namespace to be used if no namespace is supplied and the //* computed element is a string with no prefix.validation
- Required validation mode (e.g. STRICT, LAX, SKIP)inheritNamespaces
- true if child elements automatically inherit the namespaces of their parentschemaType
- The required schema type for the contentallowQName
- True if the elementName expression is allowed to return a QNameValue; false if it must return a string (that is, true in XQuery, false in XSLT).
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Method Detail
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getNameExpression
public Expression getNameExpression()
Get the expression used to compute the element name- Returns:
- the expression used to compute the element name
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getNamespaceExpression
public Expression getNamespaceExpression()
Get the expression used to compute the namespace URI- Returns:
- the expression used to compute the namespace URI
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getNamespaceResolver
public NamespaceResolver getNamespaceResolver()
Get the namespace resolver that provides the namespace bindings defined in the static context- Returns:
- the namespace resolver
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simplify
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Description copied from class:ParentNodeConstructor
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.- Overrides:
simplify
in classParentNodeConstructor
- Parameters:
visitor
- an expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) 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 parent pointer and 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 classParentNodeConstructor
- 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 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)
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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 classParentNodeConstructor
- 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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copy
public Expression copy()
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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getItemType
public ItemType getItemType(TypeHierarchy th)
Get the item type of the value returned by this instruction- Overrides:
getItemType
in classElementCreator
- Parameters:
th
- the type hierarchy cache- Returns:
- the item type
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iterateSubExpressions
public java.util.Iterator iterateSubExpressions()
Description copied from class:ParentNodeConstructor
Get the immediate sub-expressions of this expression.- Overrides:
iterateSubExpressions
in classParentNodeConstructor
- 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 classParentNodeConstructor
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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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 classParentNodeConstructor
- 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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checkPermittedContents
public void checkPermittedContents(SchemaType parentType, StaticContext env, 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 classExpression
- 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 typeenv
- the static contextwhole
- 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
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getNameCode
public int getNameCode(XPathContext context) throws XPathException
Callback from the superclass ElementCreator to get the nameCode for the element name- Specified by:
getNameCode
in classElementCreator
- Parameters:
context
- The evaluation context (not used)- Returns:
- the name code for the element name
- Throws:
XPathException
- if a failure occurs
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getNewBaseURI
public java.lang.String getNewBaseURI(XPathContext context)
Description copied from class:ElementCreator
Get the base URI for the element being constructed- Specified by:
getNewBaseURI
in classElementCreator
- Parameters:
context
- the XPath dynamic evaluation context- Returns:
- the base URI of the constructed element
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outputNamespaceNodes
protected void outputNamespaceNodes(XPathContext context, Receiver out) throws XPathException
Callback to output namespace nodes for the new element.- Specified by:
outputNamespaceNodes
in classElementCreator
- Parameters:
context
- The execution contextout
- the Receiver where the namespace nodes are to be written- Throws:
XPathException
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getInstructionNameCode
public int getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes- Overrides:
getInstructionNameCode
in classInstruction
- Returns:
- a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace
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explain
public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
explain
in classExpression
- Parameters:
out
- the expression presenter used to display the structure
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