net.sf.saxon.instruct

Class ComputedAttribute

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
Constructor Summary
ComputedAttribute(Expression attributeName, Expression namespace, NamespaceResolver nsContext, int validationAction, SimpleType schemaType, int annotation, boolean allowNameAsQName)
Construct an Attribute instruction
Method Summary
voidcheckPermittedContents(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.
intcomputeSpecialProperties()
Get the static properties of this expression (other than its type).
Expressioncopy()
Copy an expression.
intevaluateNameCode(XPathContext context)
Determine the name to be used for the attribute, as an integer name code
voidexplain(ExpressionPresenter out)
Diagnostic print of expression structure.
intgetCardinality()
Get the static cardinality of this expression
intgetInstructionNameCode()
Get the name of this instruction
ItemTypegetItemType(TypeHierarchy th)
Get the static type of this expression
ExpressiongetNameExpression()
Get the expression used to compute the name of the attribute
ExpressiongetNamespaceExpression()
Get the expression used to compute the namespace part of the name of the attribute
NamespaceResolvergetNamespaceResolver()
Get the namespace resolver used to resolve any prefix in the name of the attribute
Iterator<Expression>iterateSubExpressions()
Get the subexpressions of this expression
voidlocalTypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
protected voidpromoteInst(PromotionOffer offer)
Offer promotion for subexpressions.
booleanreplaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression
voidsetRejectDuplicates()
Indicate that two attributes with the same name are not acceptable.
Expressionsimplify(ExpressionVisitor visitor)

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

checkPermittedContents

public 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. 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.

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.

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

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Returns: the copy of the original expression

evaluateNameCode

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

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.

getCardinality

public int getCardinality()
Get the static cardinality of this expression

Returns: the static cardinality (exactly one)

getInstructionNameCode

public int getInstructionNameCode()
Get the name of this instruction

getItemType

public ItemType getItemType(TypeHierarchy th)
Get the static type of this expression

Parameters: th the type hierarchy cache

Returns: the static type of the item returned by this expression

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

iterateSubExpressions

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

Returns: an iterator over the subexpressions

localTypeCheck

public void localTypeCheck(ExpressionVisitor visitor, ItemType contextItemType)

optimize

public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)

promoteInst

protected void promoteInst(PromotionOffer offer)
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.

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

replaceSubExpression

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

Parameters: original the original subexpression replacement the replacement subexpression

Returns: true if the original subexpression is found

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)

simplify

public Expression simplify(ExpressionVisitor visitor)