Package net.sf.saxon.expr
Class AxisExpression
java.lang.Object
net.sf.saxon.expr.ComputedExpression
net.sf.saxon.expr.AxisExpression
- All Implemented Interfaces:
Serializable
,SourceLocator
,Container
,Expression
,InstructionInfoProvider
An AxisExpression is always obtained by simplifying a PathExpression.
It represents a PathExpression that starts at the context node, and uses
a simple node-test with no filters. For example "*", "title", "./item",
"@*", or "ancestor::chapter*".
An AxisExpression delivers nodes in axis order (not in document order). To get nodes in document order, in the case of a reverse axis, the expression should be wrapped in a Reverser.
- See Also:
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Field Summary
FieldsFields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionfinal int
Specify that the expression returns a singletonint
Get the static properties of this expression (other than its type).void
display
(int level, PrintStream out, Configuration config) Diagnostic print of expression structureboolean
Is this expression the same as another expression?byte
getAxis()
Get the axisGet the static type of the context item for this AxisExpression.int
Determine which aspects of the context the expression depends on.final ItemType
Determine the data type of the items returned by this expressionGet the NodeTest.int
hashCode()
get HashCode for comparing two expressionsiterate
(XPathContext context) Evaluate the path-expression in a given context to return a NodeSetoptimize
(Optimizer opt, StaticContext env, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.simplify
(StaticContext env) Simplify an expressiontoString()
Represent the expression as a string for diagnosticsRepresent the expression as a string for diagnosticstypeCheck
(StaticContext env, ItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterateSubExpressions, markTailFunctionCalls, process, promote, replaceSubExpression, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError
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Field Details
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computedCardinality
int computedCardinality
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Constructor Details
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AxisExpression
Constructor- Parameters:
axis
- The axis to be used in this AxisExpression: relevant constants are defined in class net.sf.saxon.om.Axis.nodeTest
- The conditions to be satisfied by selected nodes. May be null, indicating that any node on the axis is acceptable- See Also:
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Method Details
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simplify
Simplify an expression- Specified by:
simplify
in interfaceExpression
- Overrides:
simplify
in classComputedExpression
- Parameters:
env
- the static context- Returns:
- the simplified expression
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typeCheck
Type-check the expression- Parameters:
env
- the static context of the expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
- Throws:
XPathException
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getContextItemType
Get the static type of the context item for this AxisExpression. May be null if not known. -
optimize
Perform optimisation of an expression and its subexpressions.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.
- Parameters:
opt
- the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.env
- the static context of the expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten if appropriate to optimize execution
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equals
Is this expression the same as another expression? -
hashCode
public int hashCode()get HashCode for comparing two expressions -
getIntrinsicDependencies
public int getIntrinsicDependencies()Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE- Overrides:
getIntrinsicDependencies
in classComputedExpression
- Returns:
- a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty
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computeSpecialProperties
public int computeSpecialProperties()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.- Overrides:
computeSpecialProperties
in classComputedExpression
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getItemType
Determine the data type of the items returned by this expression- Parameters:
th
-- Returns:
- Type.NODE or a subtype, based on the NodeTest in the axis step, plus information about the content type if this is known from schema analysis
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computeCardinality
public final int computeCardinality()Specify that the expression returns a singleton- Specified by:
computeCardinality
in classComputedExpression
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getAxis
public byte getAxis()Get the axis -
getNodeTest
Get the NodeTest. Returns null if the AxisExpression can return any node. -
iterate
Evaluate the path-expression in a given context to return a NodeSet- Specified by:
iterate
in interfaceExpression
- Overrides:
iterate
in classComputedExpression
- Parameters:
context
- the evaluation context- Returns:
- a SequenceIterator that can be used to iterate over the result of the expression
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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display
Diagnostic print of expression structure- Parameters:
level
- indentation level for this expressionout
- Output destinationconfig
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toString
Represent the expression as a string for diagnostics -
toString
Represent the expression as a string for diagnostics
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