Class PathExpression

    • Constructor Detail

      • PathExpression

        public PathExpression​(Expression start,
                              Expression step)
        Constructor
        Parameters:
        start - A node-set expression denoting the absolute or relative set of nodes from which the navigation path should start.
        step - The step to be followed from each node in the start expression to yield a new node-set
    • Method Detail

      • getStartExpression

        public Expression getStartExpression()
        Get the start expression (the left-hand operand)
      • getStepExpression

        public Expression getStepExpression()
        Get the step expression (the right-hand operand)
      • getItemType

        public final ItemType getItemType​(TypeHierarchy th)
        Determine the data type of the items returned by this exprssion
        Specified by:
        getItemType in interface Expression
        Parameters:
        th -
        Returns:
        the type of the step
      • typeCheck

        public Expression typeCheck​(StaticContext env,
                                    ItemType contextItemType)
                             throws XPathException
        Optimize the expression and perform type analysis
        Specified by:
        typeCheck in interface Expression
        Parameters:
        env - the static context of the expression
        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 to perform necessary run-time type checks, and to perform other type-related optimizations
        Throws:
        StaticError - if an error is discovered during this phase (typically a type error)
        XPathException
      • optimize

        public Expression optimize​(Optimizer opt,
                                   StaticContext env,
                                   ItemType contextItemType)
                            throws XPathException
        Optimize the expression and perform type analysis
        Specified by:
        optimize in interface Expression
        Parameters:
        opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.
        env - the static context of the expression
        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:
        StaticError - if an error is discovered during this phase (typically a type error)
        XPathException
      • promote

        public Expression promote​(PromotionOffer offer)
                           throws XPathException
        Promote this expression if possible
        Specified by:
        promote in interface Expression
        Overrides:
        promote in class ComputedExpression
        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
        Returns:
        if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
        Throws:
        XPathException - if any error is detected
      • replaceSubExpression

        public boolean replaceSubExpression​(Expression original,
                                            Expression replacement)
        Replace one subexpression by a replacement subexpression
        Specified by:
        replaceSubExpression in interface Container
        Overrides:
        replaceSubExpression in class ComputedExpression
        Parameters:
        original - the original subexpression
        replacement - the replacement subexpression
        Returns:
        true if the original subexpression is found
      • computeDependencies

        public int computeDependencies()
        Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE
        Overrides:
        computeDependencies in class ComputedExpression
        Returns:
        the depencies, as a bit-mask
      • 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 ComputedExpression
      • equals

        public boolean equals​(java.lang.Object other)
        Is this expression the same as another expression?
        Overrides:
        equals in class java.lang.Object
      • hashCode

        public int hashCode()
        get HashCode for comparing two expressions
        Overrides:
        hashCode in class java.lang.Object
      • getFirstStep

        public Expression getFirstStep()
        Get the first step in this expression. A path expression A/B/C is represented as (A/B)/C, but the first step is A
      • getRemainingSteps

        public Expression getRemainingSteps()
        Get all steps after the first. This is complicated by the fact that A/B/C is represented as ((A/B)/C; we are required to return B/C
      • getLastStep

        public Expression getLastStep()
        Get the last step of the path expression
      • getLeadingSteps

        public Expression getLeadingSteps()
        Get a path expression consisting of all steps except the last
      • isAbsolute

        public boolean isAbsolute​(TypeHierarchy th)
        Test whether a path expression is an absolute path - that is, a path whose first step selects a document node
      • map

        public SequenceIterator map​(XPathContext context)
                             throws XPathException
        Mapping function, from a node returned by the start iteration, to a sequence returned by the child.
        Specified by:
        map in interface ContextMappingFunction
        Parameters:
        context - The processing context. The item to be mapped is the context item identified from this context: the values of position() and last() also relate to the set of items being mapped
        Returns:
        a SequenceIterator over the sequence of items that the supplied input item maps to
        Throws:
        XPathException
      • display

        public void display​(int level,
                            java.io.PrintStream out,
                            Configuration config)
        Diagnostic print of expression structure
        Specified by:
        display in interface Expression
        Parameters:
        level - indentation level for this expression
        out - Output destination