net.sf.saxon.instruct
Class ComputedAttribute

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.instruct.Instruction
          extended by net.sf.saxon.instruct.SimpleNodeConstructor
              extended by net.sf.saxon.instruct.AttributeCreator
                  extended by net.sf.saxon.instruct.ComputedAttribute
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, DivisibleInstruction, TailCallReturner, InstructionInfo, Locator

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

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.instruct.SimpleNodeConstructor
select
 
Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
 
Constructor Summary
ComputedAttribute(Expression attributeName, Expression namespace, NamespaceResolver nsContext, int validationAction, SimpleType schemaType, int annotation, boolean allowNameAsQName)
          Construct an Attribute instruction
 
Method Summary
 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.
 int computeSpecialProperties()
          Get the static properties of this expression (other than its type).
 Expression copy()
          Copy an expression.
 int evaluateNameCode(XPathContext context)
          Determine the name to be used for the attribute, as an integer name code
 void explain(ExpressionPresenter out)
          Diagnostic print of expression structure.
 int getCardinality()
          Get the static cardinality of this expression
 int getInstructionNameCode()
          Get the name of this instruction
 ItemType getItemType(TypeHierarchy th)
          Get the static type of this expression
 Expression getNameExpression()
          Get the expression used to compute the name of the attribute
 Expression getNamespaceExpression()
          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
 Iterator<Expression> iterateSubExpressions()
          Get the subexpressions of this expression
 void localTypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
          Method to perform type-checking specific to the kind of instruction
 Expression 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 subexpression
 void setRejectDuplicates()
          Indicate that two attributes with the same name are not acceptable.
 Expression simplify(ExpressionVisitor visitor)
          Simplify an expression.
 
Methods inherited from class net.sf.saxon.instruct.AttributeCreator
getAnnotation, getOptions, getSchemaType, getValidationAction, processValue, setAnnotation, setNoSpecialChars, setOptions, setSchemaType, setValidationAction
 
Methods inherited from class net.sf.saxon.instruct.SimpleNodeConstructor
checkContent, computeCardinality, createsNewNodes, evaluateItem, expandChildren, getSelect, iterate, processLeavingTail, processLeft, processRight, setSelect, typeCheck
 
Methods inherited from class net.sf.saxon.instruct.Instruction
assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getConstructType, getImplementationMethod, getSourceLocator, isXSLT, process, promote
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, getColumnNumber, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError
 
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
 

Constructor Detail

ComputedAttribute

public ComputedAttribute(Expression attributeName,
                         Expression namespace,
                         NamespaceResolver nsContext,
                         int validationAction,
                         SimpleType schemaType,
                         int annotation,
                         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.
annotation - Integer code identifying the type named in the type attribute
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

getNameExpression

public Expression getNameExpression()
Get the expression used to compute the name of the attribute

Returns:
the expression used to compute the name of the attribute

getNamespaceExpression

public Expression getNamespaceExpression()
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

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(TypeHierarchy th)
Get the static type of this expression

Overrides:
getItemType in class Instruction
Parameters:
th - the type hierarchy cache
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)

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 SimpleNodeConstructor
Returns:
a set of flags indicating static properties of this expression

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.

Overrides:
simplify in class SimpleNodeConstructor
Parameters:
visitor - an expression visitor
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

localTypeCheck

public void localTypeCheck(ExpressionVisitor visitor,
                           ItemType 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

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 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

iterateSubExpressions

public Iterator<Expression> iterateSubExpressions()
Get the subexpressions of this expression

Overrides:
iterateSubExpressions in class SimpleNodeConstructor
Returns:
an iterator over the subexpressions

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
Replace one subexpression by a replacement subexpression

Overrides:
replaceSubExpression in class SimpleNodeConstructor
Parameters:
original - the original subexpression
replacement - the replacement subexpression
Returns:
true if the original subexpression is found

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 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,
                                   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 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
env - the static context
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

evaluateNameCode

public int evaluateNameCode(XPathContext context)
                     throws XPathException
Determine the name to be used for the attribute, as an integer name code

Overrides:
evaluateNameCode in class SimpleNodeConstructor
Parameters:
context - Dynamic evaluation context
Returns:
the integer name code for the attribute name
Throws:
XPathException

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 class Expression
Parameters:
out - the expression presenter used to display the structure


Copyright (c) Saxonica Limited. All rights reserved.