Class NodeSetPattern

  • All Implemented Interfaces:
    ExportAgent, Locatable, IdentityComparable, Traceable

    public class NodeSetPattern
    extends Pattern
    A NodeSetPattern is a pattern based on an expression that is evaluated to return a set of nodes; a node matches the pattern if it is a member of this node-set.

    In XSLT 2.0 there are two forms of NodeSetPattern allowed, represented by calls on the id() and key() functions. In XSLT 3.0, additional forms are allowed, for example a variable reference, and a call to the doc() function. This class provides the general capability to use any expression at the head of a pattern. This is used also to support streaming, where streaming XPath expressions are mapped to patterns.

    • Constructor Detail

      • NodeSetPattern

        public NodeSetPattern​(Expression exp)
        Create a node-set pattern.
        Parameters:
        exp - an expression that can be evaluated to return a node-set; a node matches the pattern if it is present in this node-set. The expression must not depend on the focus, though it can depend on other aspects of the dynamic context such as local or global variables.
    • Method Detail

      • operands

        public java.lang.Iterable<Operand> operands()
        Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation works off the results of iterateSubExpressions()

        If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

        Overrides:
        operands in class Expression
        Returns:
        an iterator containing the sub-expressions of this expression
      • getSelectionExpression

        public Expression getSelectionExpression()
        Get the underlying expression
        Returns:
        the expression that returns all the selected nodes
      • typeCheck

        public Pattern typeCheck​(ExpressionVisitor visitor,
                                 ContextItemStaticInfo contextItemType)
                          throws XPathException
        Type-check the pattern. Default implementation does nothing. This is only needed for patterns that contain variable references or function calls.
        Overrides:
        typeCheck in class Pattern
        Parameters:
        visitor - the expression visitor
        contextItemType - the type of the context item at the point where the pattern is defined. Set to null if it is known that the context item is undefined.
        Returns:
        the optimised Pattern
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)
      • optimize

        public Pattern optimize​(ExpressionVisitor visitor,
                                ContextItemStaticInfo contextInfo)
                         throws XPathException
        Description copied from class: Pattern
        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 Pattern
        Parameters:
        visitor - an expression visitor
        contextInfo - 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)
      • setItemType

        public void setItemType​(ItemType type)
        Set the item type, that is, the type of nodes/items which the pattern will match
        Parameters:
        type - the item type that the pattern will match
      • getDependencies

        public int getDependencies()
        Get the dependencies of the pattern. The only possible dependency for a pattern is on local variables. This is analyzed in those patterns where local variables may appear.
        Overrides:
        getDependencies in class Pattern
        Returns:
        the dependencies, as a bit-significant mask
      • isMotionless

        public boolean isMotionless()
        Test whether a pattern is motionless, that is, whether it can be evaluated against a node without repositioning the input stream. This is a necessary condition for patterns used as the match pattern of a streamed template rule.
        Overrides:
        isMotionless in class Pattern
        Returns:
        true if the pattern is motionless, that is, if it can be evaluated against a streamed node without changing the position in the streamed input file
      • allocateSlots

        public int allocateSlots​(SlotManager slotManager,
                                 int nextFree)
        Allocate slots to any variables used within the pattern
        Overrides:
        allocateSlots in class Pattern
        Parameters:
        slotManager - the slot manager representing the stack frame for local variables
        nextFree - the next slot that is free to be allocated @return the next slot that is free to be allocated
        Returns:
        the next slot that is free to be allocated
      • matches

        public boolean matches​(Item item,
                               XPathContext context)
                        throws XPathException
        Determine whether this Pattern matches the given Node
        Specified by:
        matches in class Pattern
        Parameters:
        item - The NodeInfo representing the Element or other node to be tested against the Pattern
        context - The dynamic context.
        Returns:
        true if the node matches the Pattern, false otherwise
        Throws:
        XPathException - if an error occurs while matching the pattern
      • getUType

        public UType getUType()
        Get a UType indicating which kinds of items this Pattern can match.
        Specified by:
        getUType in class Pattern
        Returns:
        a UType indicating all the primitive types of item that the pattern can match.
      • getItemType

        public ItemType getItemType()
        Get a NodeTest that all the nodes matching this pattern must satisfy
        Specified by:
        getItemType in class Pattern
        Returns:
        an ItemType, as specific as possible, which all the matching items satisfy
      • equals

        public boolean equals​(java.lang.Object other)
        Determine whether this pattern is the same as another pattern
        Overrides:
        equals in class Expression
        Parameters:
        other - the other object
        Returns:
        true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.
      • computeHashCode

        protected int computeHashCode()
        Hashcode supporting equals()
        Overrides:
        computeHashCode in class Expression
        Returns:
        a computed hash code
      • copy

        public Pattern copy​(RebindingMap rebindings)
        Copy a pattern. This makes a deep copy.
        Specified by:
        copy in class Pattern
        Parameters:
        rebindings - variable bindings to be changed if encountered
        Returns:
        the copy of the original pattern
      • export

        public void export​(ExpressionPresenter presenter)
                    throws XPathException
        Description copied from class: Expression
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Specified by:
        export in interface ExportAgent
        Specified by:
        export in class Pattern
        Parameters:
        presenter - the expression presenter used to display the structure
        Throws:
        XPathException - if the export fails, for example if an expression is found that won't work in the target environment.