net.sf.saxon.value
Class SingletonNode

java.lang.Object
  net.sf.saxon.value.Value
      net.sf.saxon.value.SingletonNode

All Implemented Interfaces:

Serializable, Expression

public class SingletonNode
extends Value

A value that is a sequence containing zero or one nodes

See Also:

Serialized Form

Field Summary

protected NodeInfo

node

Constructor Summary

SingletonNode(NodeInfo node)
Create a node-set containing zero or one nodes

Method Summary

int	conversionPreference(Class required) Get conversion preference for this value to a Java class.
Object	convertToJava(Class target) Convert to Java object (for passing to external functions)
void	display(int depth, NamePool pool) Diagnostic display
boolean	effectiveBooleanValue(XPathContext context) Get the effective boolean value
String	evaluateAsString(XPathContext context) Evaluate an expression as a String.
Item	evaluateItem(XPathContext context) Evaluate as an item
int	getCardinality() Determine the static cardinality
ItemType	getItemType() Determine the data type of the items in the expression
NodeInfo	getNode() Get the node that forms the node-set.
int	getSpecialProperties() Get the static properties of this expression (other than its type).
SequenceIterator	iterate(XPathContext context) Return an enumeration of this nodeset value.

Methods inherited from class net.sf.saxon.value.Value

analyze, asItem, asValue, collapseWhitespace, getDependencies, getSubExpressions, inverse, normalizeWhitespace, promote, simplify, stringToInteger, stringToNumber, trimWhitespace

Methods inherited from class java.lang.Object

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

Field Detail

node

protected NodeInfo node

Constructor Detail

SingletonNode

public SingletonNode(NodeInfo node)

Create a node-set containing zero or one nodes

Parameters:

node - The node to be contained in the node-set, or null if the node-set is to be empty

Method Detail

getItemType

public ItemType getItemType()

Determine the data type of the items in the expression

Returns:

Type.NODE

getCardinality

public int getCardinality()

Determine the static cardinality

Returns:

one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

getNode

public NodeInfo getNode()

Get the node that forms the node-set. Return null if there is none.

getSpecialProperties

public int getSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

Specified by:

getSpecialProperties in interface Expression

Overrides:

getSpecialProperties in class Value

Returns:

a set of flags indicating static properties of this expression

iterate

public SequenceIterator iterate(XPathContext context)

Return an enumeration of this nodeset value.

Parameters:

context - supplies the context for evaluation

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

evaluateItem

public Item evaluateItem(XPathContext context)

Evaluate as an item

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)

Get the effective boolean value

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the effective boolean value

evaluateAsString

public String evaluateAsString(XPathContext context)
                        throws XPathException

Evaluate an expression as a String. This function must only be called in contexts where it is known that the expression will return a single string (or where an empty sequence is to be treated as a zero-length string). Implementations should not attempt to convert the result to a string, other than converting () to "". This method is used mainly to evaluate expressions produced by compiling an attribute value template.

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the value of the expression, evaluated in the current context. The expression must return a string or (); if the value of the expression is (), this method returns "".

Throws:

XPathException - if any dynamic error occurs evaluating the expression

display

public void display(int depth,
                    NamePool pool)

Diagnostic display

Parameters:

depth - indentation level for this expression

conversionPreference

public int conversionPreference(Class required)

Get conversion preference for this value to a Java class. A low result indicates higher preference.

Specified by:

conversionPreference in class Value

convertToJava

public Object convertToJava(Class target)
                     throws XPathException

Convert to Java object (for passing to external functions)

Specified by:

convertToJava in class Value

Parameters:

target - The class required by the external function

Returns:

an object of the target class

Throws:

XPathException