Class SimpleNodeConstructor

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, TailCallReturner, InstructionInfo, Locator
Direct Known Subclasses:
AttributeCreator, Comment, NamespaceConstructor, 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:
  • Field Details

  • Constructor Details

    • SimpleNodeConstructor

      public SimpleNodeConstructor()
      Default constructor used by subclasses
  • Method Details

    • setSelect

      public void setSelect(Expression select, Configuration config)
      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 node
      config - the Saxon configuration (used for example to do early validation of the content of an attribute against the schema-defined type)
    • getContentExpression

      public Expression getContentExpression()
      Get the expression that determines the string value of the constructed node
      Returns:
      the select expression
    • createsNewNodes

      public final boolean createsNewNodes()
      Determine whether this instruction creates new nodes. This implementation returns true.
      Overrides:
      createsNewNodes in class Instruction
      Returns:
      true if the instruction creates new nodes (or if it can't be proved that it doesn't)
    • computeCardinality

      public int computeCardinality()
      Get the cardinality of the sequence returned by evaluating this instruction
      Overrides:
      computeCardinality in class Instruction
      Returns:
      the static cardinality
    • 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 class Instruction
      Parameters:
      visitor - an expression visitor
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • 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 Instruction
      Returns:
      a set of flags indicating static properties of this expression
    • localTypeCheck

      public abstract void localTypeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Method to perform type-checking specific to the kind of instruction
      Parameters:
      visitor - an expression visitor
      contextItemType - the static type of the context item
      Throws:
      XPathException - if a type error is detected
    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType 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 class Expression
      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 rewritten expression
      Throws:
      XPathException - if any static errors are found in this expression or any of its children
    • 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 Expression
      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)
    • iterateSubExpressions

      public Iterator<Expression> 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 class Expression
      Returns:
      an iterator containing the sub-expressions of this expression
    • replaceSubExpression

      public boolean replaceSubExpression(Expression original, Expression replacement)
      Replace one subexpression by a replacement subexpression
      Overrides:
      replaceSubExpression in class Expression
      Parameters:
      original - the original subexpression
      replacement - the replacement subexpression
      Returns:
      true if the original subexpression is found
    • processLeavingTail

      public TailCall processLeavingTail(XPathContext context) throws XPathException
      Process this instruction
      Specified by:
      processLeavingTail in interface TailCallReturner
      Specified by:
      processLeavingTail in class Instruction
      Parameters:
      context - the dynamic context of the transformation
      Returns:
      a TailCall to be executed by the caller, always null for this instruction
      Throws:
      XPathException - if a dynamic error occurs during the evaluation of the instruction
    • processValue

      public abstract void processValue(CharSequence value, XPathContext context) throws XPathException
      Process the value of the node, to create the new node.
      Parameters:
      value - the string value of the new node
      context - the dynamic evaluation context
      Throws:
      XPathException - if a dynamic error occurs
    • evaluateItem

      public NodeInfo evaluateItem(XPathContext context) throws XPathException
      Evaluate as an expression.
      Overrides:
      evaluateItem in class Instruction
      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
    • checkContent

      protected String checkContent(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 content
      context - the dynamic context
      Returns:
      the original content, unless adjustments are needed
      Throws:
      XPathException - if the content is invalid
    • evaluateNodeName

      public NodeName evaluateNodeName(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
    • iterate

      public SequenceIterator<NodeInfo> 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.
      Overrides:
      iterate in class Instruction
      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
    • 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 Instruction
      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