Package net.sf.saxon.value
Class SingletonNode
- java.lang.Object
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- net.sf.saxon.value.Value
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- net.sf.saxon.value.SingletonNode
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- All Implemented Interfaces:
java.io.Serializable
,Expression
,ValueRepresentation
public class SingletonNode extends Value
A value that is a sequence containing zero or one nodes- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description protected NodeInfo
node
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Fields inherited from class net.sf.saxon.value.Value
EMPTY_CLASS_ARRAY
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Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Fields inherited from interface net.sf.saxon.om.ValueRepresentation
EMPTY_VALUE_ARRAY
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Constructor Summary
Constructors Constructor Description SingletonNode(NodeInfo node)
Create a node-set containing zero or one nodes
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Object
convertToJava(java.lang.Class target, XPathContext context)
Convert to Java object (for passing to external functions)void
display(int depth, java.io.PrintStream out, Configuration config)
Diagnostic displayboolean
effectiveBooleanValue(XPathContext context)
Get the effective boolean valuejava.lang.String
evaluateAsString(XPathContext context)
Evaluate an expression as a String.Item
evaluateItem(XPathContext context)
Evaluate as an itemint
getCardinality()
Determine the static cardinalityint
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().ItemType
getItemType(TypeHierarchy th)
Determine the data type of the items in the expression.int
getLength()
Get the length of the sequenceNodeInfo
getNode()
Get the node that forms the node-set.int
getSpecialProperties()
Get the static properties of this expression (other than its type).java.lang.String
getStringValue()
Convert the value to a string, using the serialization rules.Item
itemAt(int n)
Get the n'th item in the sequence (starting from 0).SequenceIterator
iterate(XPathContext context)
Return an enumeration of this nodeset value.void
process(XPathContext context)
Process the instruction, without returning any tail calls-
Methods inherited from class net.sf.saxon.value.Value
asItem, asIterator, asValue, checkPermittedContents, convert, convertJavaObjectToXPath, equals, getDependencies, getIterator, getParentExpression, getStringValueCS, hashCode, iterateSubExpressions, makeQNameValue, optimize, promote, reduce, simplify, stringToNumber, toString, typeCheck
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Field Detail
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node
protected NodeInfo node
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Constructor Detail
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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
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Method Detail
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getImplementationMethod
public int getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is prefered.
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process
public void process(XPathContext context) throws XPathException
Process the instruction, without returning any tail calls- Specified by:
process
in interfaceExpression
- Overrides:
process
in classValue
- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
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getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the items in the expression. This method determines the most precise type that it can, because it is called when testing that the node conforms to a required type.- Specified by:
getItemType
in interfaceExpression
- Overrides:
getItemType
in classValue
- Parameters:
th
-- Returns:
- the most precise possible type of the node.
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getCardinality
public int getCardinality()
Determine the static cardinality- Specified by:
getCardinality
in interfaceExpression
- Overrides:
getCardinality
in classValue
- Returns:
- one of the values
StaticProperty.ALLOWS_ONE
,StaticProperty.ALLOWS_ZERO_OR_MORE
,StaticProperty.ALLOWS_ZERO_OR_ONE
,StaticProperty.ALLOWS_ONE_OR_MORE
,StaticProperty.EMPTY
. This default implementation returns ZERO_OR_MORE (which effectively gives no information).
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getLength
public int getLength() throws XPathException
Get the length of the sequence- Overrides:
getLength
in classValue
- Throws:
XPathException
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itemAt
public Item itemAt(int n) throws XPathException
Get the n'th item in the sequence (starting from 0). This is defined for all SequenceValues, but its real benefits come for a SequenceValue stored extensionally (or for a MemoClosure, once all the values have been read)- Overrides:
itemAt
in classValue
- Throws:
XPathException
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getNode
public NodeInfo getNode()
Get the node that forms the node-set. Return null if there is none.
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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 interfaceExpression
- Overrides:
getSpecialProperties
in classValue
- Returns:
StaticProperty.NON_CREATIVE
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iterate
public SequenceIterator iterate(XPathContext context)
Return an enumeration of this nodeset value.- Parameters:
context
- The context in which the expression is to be evaluated. Note that this context must contain a stackframe with sufficient slots to allow evaluation of any variables contained in the expression (including variables allocated internally by the optimizer)- Returns:
- a SequenceIterator that can be used to iterate over the result of the expression
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evaluateItem
public Item evaluateItem(XPathContext context)
Evaluate as an item- Specified by:
evaluateItem
in interfaceExpression
- Overrides:
evaluateItem
in classValue
- Parameters:
context
- The context in which the expression is to be evaluated. Note that this context must contain a stackframe with sufficient slots to allow evaluation of any variables contained in the expression (including variables allocated internally by the optimizer)- Returns:
- the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
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effectiveBooleanValue
public boolean effectiveBooleanValue(XPathContext context)
Get the effective boolean value- Specified by:
effectiveBooleanValue
in interfaceExpression
- Overrides:
effectiveBooleanValue
in classValue
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- the effective boolean value
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getStringValue
public java.lang.String getStringValue()
Convert the value to a string, using the serialization rules. For atomic values this is the same as a cast; for sequence values it gives a space-separated list. For QNames and NOTATIONS, or lists containing them, it fails.- Specified by:
getStringValue
in interfaceValueRepresentation
- Overrides:
getStringValue
in classValue
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evaluateAsString
public java.lang.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.- Specified by:
evaluateAsString
in interfaceExpression
- Overrides:
evaluateAsString
in classValue
- 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
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display
public void display(int depth, java.io.PrintStream out, Configuration config)
Diagnostic display- Specified by:
display
in interfaceExpression
- Overrides:
display
in classValue
- Parameters:
depth
- indentation level for this expressionout
- Output destination
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convertToJava
public java.lang.Object convertToJava(java.lang.Class target, XPathContext context) throws XPathException
Convert to Java object (for passing to external functions)- Overrides:
convertToJava
in classValue
- Throws:
XPathException
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