Class JAXPVariable

java.lang.Object
net.sf.saxon.xpath.JAXPVariable
All Implemented Interfaces:
Binding, VariableDeclaration

public final class JAXPVariable extends 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 Details

    • JAXPVariable

      public JAXPVariable(QNameValue name, XPathVariableResolver resolver)
      Private constructor: for use only be the protected factory method make()
  • Method Details

    • 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
    • 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
    • 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
    • getVariableName

      public String getVariableName()
      Get the name of the variable. Used for diagnostic purposes only.
      Specified by:
      getVariableName in interface VariableDeclaration
      Returns:
      the name of the variable, as a string (containing the raw QName)
    • getNameCode

      public int getNameCode()
      Establish the fingerprint of the name of this variable. Dummy implementation, not used.
      Specified by:
      getNameCode in interface VariableDeclaration
      Returns:
      -1, always
    • 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
    • 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
    • makeQName

      QName makeQName(QNameValue in)