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java.lang.Object net.sf.saxon.expr.Expression net.sf.saxon.expr.SingleNodeExpression
public abstract class SingleNodeExpression
A node set expression that will always return zero or one nodes
Field Summary |
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Fields inherited from class net.sf.saxon.expr.Expression |
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EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD |
Constructor Summary | |
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SingleNodeExpression()
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Method Summary | |
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int |
computeCardinality()
Specify that the expression returns a singleton |
int |
computeSpecialProperties()
Compute the special properties of this expression. |
boolean |
effectiveBooleanValue(XPathContext context)
Get the effective boolean value of the expression. |
Item |
evaluateItem(XPathContext context)
Evaluate an expression as a single item. |
int |
getIntrinsicDependencies()
Determine which aspects of the context the expression depends on. |
ItemType |
getItemType(TypeHierarchy th)
Determine the data type of the items returned by this expression |
abstract NodeInfo |
getNode(XPathContext context)
Get the single node to which this expression refers. |
boolean |
isContextPossiblyUndefined()
Ask whether there is a possibility that the context item will be undefined |
SequenceIterator |
iterate(XPathContext context)
Evaluate the expression in a given context to return an iterator |
protected abstract String |
noContextMessage()
Customize the error message on type checking |
Expression |
optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
Expression |
typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Type-check the expression. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public SingleNodeExpression()
Method Detail |
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public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
typeCheck
in class Expression
visitor
- an expression visitorcontextItemType
- the static type of "." at the point where this expression is invoked.
The parameter is set to null if it is known statically that the context item will be undefined.
If the type of the context item is not known statically, the argument is set to
Type.ITEM_TYPE
XPathException
- if an error is discovered during this phase
(typically a type error)protected abstract String noContextMessage()
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
optimize
in class Expression
visitor
- an expression visitorcontextItemType
- the static type of "." at the point where this expression is invoked.
The parameter is set to null if it is known statically that the context item will be undefined.
If the type of the context item is not known statically, the argument is set to
Type.ITEM_TYPE
XPathException
- if an error is discovered during this phase
(typically a type error)public int computeCardinality()
computeCardinality
in class Expression
StaticProperty.ALLOWS_ZERO_OR_ONE
,
StaticProperty.EXACTLY_ONE
, StaticProperty.ALLOWS_ONE_OR_MORE
,
StaticProperty.ALLOWS_ZERO_OR_MORE
public ItemType getItemType(TypeHierarchy th)
getItemType
in class Expression
th
- the type hierarchy cache
public int getIntrinsicDependencies()
getIntrinsicDependencies
in class Expression
public int computeSpecialProperties()
Expression
StaticProperty
. The "special" properties are properties
other than cardinality and dependencies, and most of them relate to properties of node sequences, for
example whether the nodes are in document order.
computeSpecialProperties
in class Expression
public abstract NodeInfo getNode(XPathContext context) throws XPathException
XPathException
public boolean isContextPossiblyUndefined()
public SequenceIterator iterate(XPathContext context) throws XPathException
iterate
in class Expression
context
- the evaluation context
XPathException
- if any dynamic error occurs evaluating the
expressionpublic Item evaluateItem(XPathContext context) throws XPathException
Expression
evaluateItem
in class Expression
context
- The context in which the expression is to be evaluated
XPathException
- if any dynamic error occurs evaluating the
expressionpublic boolean effectiveBooleanValue(XPathContext context) throws XPathException
Expression
effectiveBooleanValue
in class Expression
context
- The context in which the expression is to be evaluated
XPathException
- if any dynamic error occurs evaluating the
expression
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