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## 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
`protected` | `JAXPVariable(StructuredQName 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.
`SequenceType` | `getRequiredType()` Get the declared type of the variable
`StructuredQName` | `getVariableQName()` Get the name of the variable as a structured QName
`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
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### JAXPVariable

    protected JAXPVariable(StructuredQName name,
                           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

### getVariableQName

    public StructuredQName getVariableQName()

  Get the name of the variable as a structured QName

  Specified by:
    `getVariableQName` in interface `Binding`
  Specified by:
    `getVariableQName` in interface `VariableDeclaration`
  Returns:
    the variable name

### 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`

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Copyright (c) 2004-2010 Saxonica Limited. All rights reserved.