Class JAXPVariable

  • All Implemented Interfaces:
    Binding, VariableDeclaration

    public final class JAXPVariable
    extends java.lang.Object
    implements VariableDeclaration, Binding
    An object representing an XPath variable for use in the JAXP XPath API. The object is created at compile time when the parser tries to bind a variable reference; the value is fetched at run-time from the XPathVariableResolver. With this interface, there is no way of reporting a static error if the variable has not been declared.

    In Saxon terms, this class is both a VariableDeclaration and a Binding. Unlike a normal VariableDeclaration, it isn't created in advance, but is created on demand when the parser encounters a variable reference. This actually means that if the XPath expression contains two references to the same variable, two VariableDeclarations will be created; however, they will be indistinguishable to the VariableResolver. Acting as a VariableDeclaration, the object goes through the motions of fixing up a binding to a variable reference (in practice, of course, there is exactly one reference to the variable). Acting as a run-time binding, it then evaluates the variable by calling the XPathVariableResolver supplied by the API caller. If no XPathVariableResolver was supplied, an error is reported when a variable is encountered; but if the variable resolver doesn't recognize the variable name, it returns null, which is treated as an empty sequence.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected JAXPVariable​(StructuredQName name, javax.xml.xpath.XPathVariableResolver resolver)
      Private constructor: for use only be the protected factory method make()
    • Constructor Detail

      • JAXPVariable

        protected JAXPVariable​(StructuredQName name,
                               javax.xml.xpath.XPathVariableResolver resolver)
        Private constructor: for use only be the protected factory method make()
        Parameters:
        name - the name of the variable
        resolver - the resolver used in conjunction with this variable
    • Method Detail

      • getRequiredType

        public SequenceType getRequiredType()
        Description copied from interface: Binding
        Get the declared type of the variable
        Specified by:
        getRequiredType in interface Binding
        Returns:
        the declared type
      • isGlobal

        public boolean isGlobal()
        Indicate whether the binding is local or global. A global binding is one that has a fixed value for the life of a query or transformation; any other binding is local.
        Specified by:
        isGlobal in interface Binding
        Returns:
        true if the binding is global
      • isAssignable

        public final boolean isAssignable()
        Test whether it is permitted to assign to the variable using the saxon:assign extension element. This will only be for an XSLT global variable where the extra attribute saxon:assignable="yes" is present.
        Specified by:
        isAssignable in interface Binding
        Returns:
        true if the binding is assignable
      • getLocalSlotNumber

        public int getLocalSlotNumber()
        If this is a local variable held on the local stack frame, return the corresponding slot number. In other cases, return -1.
        Specified by:
        getLocalSlotNumber in interface Binding
        Returns:
        the slot number on the local stack frame
      • addReference

        public void addReference​(boolean isLoopingReference)
        Description copied from interface: Binding
        Register a variable reference that refers to the variable bound in this expression
        Specified by:
        addReference in interface Binding
        Parameters:
        isLoopingReference - - true if the reference occurs within a loop, such as the predicate of a filter expression
      • registerReference

        public void registerReference​(BindingReference ref)
        Method called by the XPath expression parser to register a reference to this variable. This method should not be called by users of the API.
        Specified by:
        registerReference in interface VariableDeclaration
        Parameters:
        ref - the variable reference
      • evaluateVariable

        public ValueRepresentation evaluateVariable​(XPathContext context)
                                             throws XPathException
        Get the value of the variable. This method is used by the XPath execution engine to retrieve the value.
        Specified by:
        evaluateVariable in interface Binding
        Parameters:
        context - The dynamic evaluation context
        Returns:
        The value of the variable
        Throws:
        XPathException - if an error occurs while evaluating the variable
      • getIntegerBoundsForVariable

        public IntegerValue[] getIntegerBoundsForVariable()
        If the variable is bound to an integer, get the minimum and maximum possible values. Return null if unknown or not applicable
        Specified by:
        getIntegerBoundsForVariable in interface Binding
        Returns:
        a pair of integers containing the minimum and maximum values for the integer value; or null if the value is not an integer or the range is unknown
      • makeQName

        javax.xml.namespace.QName makeQName​(QNameValue in)
        Construct a JAXP QName from a Saxon QNameValue
        Parameters:
        in - the Saxon QNameValue
        Returns:
        the JAXP QName