Package net.sf.saxon.sxpath

Class XPathExpression

  • public class XPathExpression
extends java.lang.Object
    This class is a representation of an XPath Expression for use with the XPathEvaluator class. It is modelled on the XPath API defined in JAXP 1.3, but is free-standing, and is more strongly typed.

    In Saxon 9.6, the methods that returned Object and did implicit conversion to a native Java object have been removed; all conversions must now be done explicitly.

    • Constructor Detail

      • XPathExpression

        protected XPathExpression​(StaticContext env,
                          Expression exp,
                          Executable exec)
        The constructor is protected, to ensure that instances can only be created using the createExpression() or createPattern() method of XPathEvaluator
        Parameters:
        env - the static context of the expression
        exp - the internal representation of the compiled expression
        exec - the Executable associated with this expression

    • Method Detail

      • getExecutable

        public Executable getExecutable()
        Get the Executable associated with this expression
        Returns:
        the associated Executable

      • setStackFrameMap

        protected void setStackFrameMap​(SlotManager map,
                                int numberOfExternalVariables)
        Define the number of slots needed for local variables within the expression
        Parameters:
        map - the stack frame map identifying all the variables used by the expression, both those declared internally, and references to variables declared externally
        numberOfExternalVariables - the number of slots in the stack frame allocated to externally-declared variables. These must be assigned a value before execution starts

      • createDynamicContext

        public XPathDynamicContext createDynamicContext()
        Create a dynamic context suitable for evaluating this expression, without supplying a context item
        Returns:
        an XPathDynamicContext object representing a suitable dynamic context. This will be initialized with a stack frame suitable for holding the variables used by the expression.

      • createDynamicContext

        public XPathDynamicContext createDynamicContext​(Item contextItem)
                                         throws XPathException
        Create a dynamic context suitable for evaluating this expression
        Parameters:
        contextItem - the initial context item, which may be null if no context item is required, or if it is to be supplied later
        Returns:
        an XPathDynamicContext object representing a suitable dynamic context. This will be initialized with a stack frame suitable for holding the variables used by the expression.
        Throws:
        XPathException - if the context item does not match the required context item type set up in the static context

      • createDynamicContext

        public XPathDynamicContext createDynamicContext​(Controller controller,
                                                Item contextItem)
                                         throws XPathException
        Create a dynamic context suitable for evaluating this expression within an environment represented by an existing controller. The dynamic context will inherit properties of the Controller such as the current error listener, URI resolver, document pool, and implicit timezone.
        Parameters:
        controller - an existing controller. May be null, in which case the method is equivalent to calling createDynamicContext(net.sf.saxon.om.Item)
        contextItem - the initial context item, which may be null if no context item is required, or if it is to be supplied later
        Returns:
        an XPathDynamicContext object representing a suitable dynamic context. This will be initialized with a stack frame suitable for holding the variables used by the expression.
        Throws:
        XPathException - if the context item does not match the required context item type set up in the static context
        Since:
        9.2

      • iterate

        public SequenceIterator iterate​(XPathDynamicContext context)
                         throws XPathException
        Execute the expression, returning the result as a SequenceIterator, whose members will be instances of the class Item

        Note that if evaluation of the expression fails with a dynamic error, this will generally be reported in the form of an exception thrown by the next() method of the SequenceIterator

        Parameters:
        context - the XPath dynamic context
        Returns:
        an iterator over the result of the expression
        Throws:
        XPathException - if a dynamic error occurs during the expression evaluation (though in many cases, the error will only be detected when the iterator is actually used).

      • evaluate

        public java.util.List<Item> evaluate​(XPathDynamicContext context)
                              throws XPathException
        Execute the expression, returning the result as a List, whose members will be instances of the class Item
        Parameters:
        context - the XPath dynamic context
        Returns:
        a list of items representing the result of the expression
        Throws:
        XPathException - if a dynamic error occurs while evaluation the expression

      • evaluateSingle

        public Item evaluateSingle​(XPathDynamicContext context)
                    throws XPathException
        Execute the expression, returning the result as a single Item If the result of the expression is a sequence containing more than one item, items after the first are discarded. If the result is an empty sequence, the method returns null.
        Parameters:
        context - the XPath dynamic context
        Returns:
        the first item in the result of the expression, or null to indicate that the result is an empty sequence
        Throws:
        XPathException - if a dynamic error occurs during the expression evaluation

      • effectiveBooleanValue

        public boolean effectiveBooleanValue​(XPathDynamicContext context)
                              throws XPathException
        Evaluate the expression, returning its effective boolean value
        Parameters:
        context - the XPath dynamic context
        Returns:
        the effective boolean value of the result, as defined by the fn:boolean() function
        Throws:
        XPathException - if a dynamic error occurs, or if the result is a value for which no effective boolean value is defined

      • getInternalExpression

        public Expression getInternalExpression()
        Low-level method to get the internal Saxon expression object. This exposes a wide range of internal methods that may be needed by specialized applications, and allows greater control over the dynamic context for evaluating the expression.
        Returns:
        the underlying Saxon expression object.