net.sf.saxon.xpath
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 Summary

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

Method Summary

ValueRepresentation	evaluateVariable(XPathContext context) Get the value of the variable.
int	getLocalSlotNumber() If this is a local variable held on the local stack frame, return the corresponding slot number.
int	getNameCode() Establish the fingerprint of the name of this variable.
String	getVariableName() Get the name of the variable.
boolean	isAssignable() Test whether it is permitted to assign to the variable using the saxon:assign extension element.
boolean	isGlobal() Indicate whether the binding is local or global.
void	registerReference(BindingReference ref) Method called by the XPath expression parser to register a reference to this variable.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JAXPVariable

public JAXPVariable(QNameValue name,
                    XPathVariableResolver resolver)

Private constructor: for use only be the protected factory method make()

Method Detail

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