Class ComputedAttribute

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, TailCallReturner, ValidatingInstruction, 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:
  • Constructor Details

    • 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 Details

    • 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)
    • isAllowNameAsQName

      public boolean isAllowNameAsQName()
      Allows
      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
    • 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, ExpressionVisitor.ContextItemType 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, ExpressionVisitor.ContextItemType 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
    • evaluateItem

      public NodeInfo 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
    • 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
    • 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