net.sf.saxon.sxpath

Class XPathVariable

java.lang.Object

net.sf.saxon.sxpath.XPathVariable

All Implemented Interfaces:

Binding, LocalBinding

public final class XPathVariable
extends java.lang.Object
implements LocalBinding

An object representing an XPath variable for use in the standalone XPath API. The object can only be created by calling the declareVariable method of class IndependentContext. Note that once declared, this object is thread-safe: it does not hold the actual variable value, which means it can be used with any number of evaluations of a given XPath expression, in series or in parallel.

A variable can be given a value by calling XPathDynamicContext.setVariable(XPathVariable, net.sf.saxon.om.Sequence). Note that the value of the variable is not held in the XPathVariable object, but in the XPathDynamicContext, which means that the XPathVariable itself can be used in multiple threads.

Method Summary

Modifier and Type	Method and Description
void	addReference(VariableReference ref, boolean isLoopingReference) Method called by the XPath expression parser to register a reference to this variable.
Sequence<?>	evaluateVariable(XPathContext context) Get the value of the variable.
Sequence<?>	getDefaultValue() Get the default value of the variable
IntegerValue[]	getIntegerBoundsForVariable() If the variable is bound to an integer, get the minimum and maximum possible values.
int	getLocalSlotNumber() If this is a local variable held on the local stack frame, return the corresponding slot number.
SequenceType	getRequiredType() Get the required type of this variable.
StructuredQName	getVariableQName() Get the name of the variable as a QNameValue.
boolean	isAssignable() Test whether it is permitted to assign to the variable using the saxon:assign extension element.
boolean	isGlobal() Ask whether the binding is local or global.
boolean	isIndexedVariable() Ask whether the binding is to be indexed
protected static XPathVariable	make(StructuredQName name) Factory method, for use by the declareVariable method of class IndependentContext
void	setDefaultValue(Sequence<?> defaultValue) Set a default value for the variable, to be used if no specific value is supplied when the expression is evaluated
void	setIndexedVariable() Say that the bound value has the potential to be indexed
void	setRequiredType(SequenceType requiredType) Set the required type of this variable.
void	setSlotNumber(int slotNumber) Set the slot number allocated to this variable.

Methods inherited from class java.lang.Object

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

Method Detail

make

protected static XPathVariable make(StructuredQName name)

Factory method, for use by the declareVariable method of class IndependentContext

Parameters:

name - the name of the variable to create

Returns:

the constructed XPathVariable

isGlobal

public boolean isGlobal()

Ask 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. An XPath variable is treated as a local variable (largely because it is held on the stack frame)

Specified by:

isGlobal in interface Binding

Returns:

false (always)

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:

false (always)

setRequiredType

public void setRequiredType(SequenceType requiredType)

Set the required type of this variable. If no required type is specified, the type item()* is assumed.

Parameters:

requiredType - the required type

getRequiredType

public SequenceType getRequiredType()

Get the required type of this variable. If no required type has been specified, the type item()* is returned.

Specified by:

getRequiredType in interface Binding

Returns:

the required type of 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

setSlotNumber

public void setSlotNumber(int slotNumber)

Set the slot number allocated to this variable. This method is for internal use.

Parameters:

slotNumber - the slot number to be allocated

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 LocalBinding

Returns:

the slot number on the local stack frame

getVariableQName

public StructuredQName getVariableQName()

Get the name of the variable as a QNameValue.

Specified by:

getVariableQName in interface Binding

Returns:

the name of the variable, as a QNameValue

addReference

public void addReference(VariableReference ref,
                         boolean isLoopingReference)

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:

addReference in interface Binding

Parameters:

ref - the variable reference

isLoopingReference - - true if the reference occurs within a loop, such as the predicate of a filter expression

setDefaultValue

public void setDefaultValue(Sequence<?> defaultValue)

Set a default value for the variable, to be used if no specific value is supplied when the expression is evaluated

Parameters:

defaultValue - the default value for the variable

getDefaultValue

public Sequence<?> getDefaultValue()

Get the default value of the variable

Returns:

the default value if one has been registered, or null otherwise

evaluateVariable

public Sequence<?> evaluateVariable(XPathContext context)

Get the value of the variable. This method is used by the XPath execution engine to retrieve the value. Note that the value is not held within the variable itself, but within the dynamic context.

Specified by:

evaluateVariable in interface Binding

Parameters:

context - The dynamic evaluation context

Returns:

The value of the variable

setIndexedVariable

public void setIndexedVariable()

Say that the bound value has the potential to be indexed

Specified by:

setIndexedVariable in interface LocalBinding

isIndexedVariable

public boolean isIndexedVariable()

Ask whether the binding is to be indexed

Specified by:

isIndexedVariable in interface LocalBinding

Returns:

true if the variable value can be indexed