Package net.sf.saxon.expr
Class ItemChecker
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.UnaryExpression
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- net.sf.saxon.expr.ItemChecker
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,InstructionInfo
,org.xml.sax.Locator
public final class ItemChecker extends UnaryExpression
A ItemChecker implements the item type checking of "treat as": that is, it returns the supplied sequence, checking that all its items are of the correct type- See Also:
- Serialized Form
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Field Summary
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Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
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Fields inherited from class net.sf.saxon.expr.Expression
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
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Constructor Summary
Constructors Constructor Description ItemChecker(Expression sequence, ItemType itemType, RoleLocator role)
Constructor
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Expression
copy()
Copy an expression.boolean
equals(java.lang.Object other)
Is this expression the same as another expression?Item
evaluateItem(XPathContext context)
Evaluate as an Item.void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.java.lang.String
getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.int
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().IntegerValue[]
getIntegerBounds()
For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis.ItemType
getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expressionItemMappingFunction
getMappingFunction(XPathContext context)
Get the mapping function used to implement this item check.ItemType
getRequiredType()
Get the required typeRoleLocator
getRoleLocator()
Get the RoleLocator (used to construct error messages)int
hashCode()
get HashCode for comparing two expressions.SequenceIterator
iterate(XPathContext context)
Iterate over the sequence of valuesvoid
process(XPathContext context)
Process the instruction, without returning any tail callsExpression
simplify(ExpressionVisitor visitor)
Simplify an expressionExpression
typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Type-check the expression-
Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeCardinality, computeSpecialProperties, displayOperator, getBaseExpression, iterateSubExpressions, optimize, promote, replaceSubExpression, toString
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Constructor Detail
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ItemChecker
public ItemChecker(Expression sequence, ItemType itemType, RoleLocator role)
Constructor- Parameters:
sequence
- the expression whose value we are checkingitemType
- the required type of the items in the sequencerole
- information used in constructing an error message
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Method Detail
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getRequiredType
public ItemType getRequiredType()
Get the required type- Returns:
- the required type of the items in the sequence
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getRoleLocator
public RoleLocator getRoleLocator()
Get the RoleLocator (used to construct error messages)- Returns:
- the RoleLocator
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simplify
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Simplify an expression- Overrides:
simplify
in classUnaryExpression
- Parameters:
visitor
- an expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
Type-check the expression- Overrides:
typeCheck
in classUnaryExpression
- Parameters:
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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
- Throws:
XPathException
- if an error is discovered during this phase (typically a type error)
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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 provided. This implementation provides both iterate() and process() methods natively.- Overrides:
getImplementationMethod
in classExpression
- Returns:
- the implementation method, for example
Expression.ITERATE_METHOD
orExpression.EVALUATE_METHOD
orExpression.PROCESS_METHOD
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getIntegerBounds
public IntegerValue[] getIntegerBounds()
For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis. The default implementation returns null, meaning "unknown" or "not applicable". Other implementations return an array of two IntegerValue objects, representing the lower and upper bounds respectively. The values UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH are used to indicate values limited by the size of a string or the size of a sequence.- Overrides:
getIntegerBounds
in classExpression
- Returns:
- the lower and upper bounds of integer values in the result, or null to indicate unknown or not applicable.
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
Iterate over the sequence of values- Overrides:
iterate
in classExpression
- Parameters:
context
- supplies the context for evaluation- 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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getMappingFunction
public ItemMappingFunction getMappingFunction(XPathContext context)
Get the mapping function used to implement this item check. This mapping function is applied to each item in the input sequence.- Parameters:
context
- The dynamic context used to evaluate the mapping function- Returns:
- the mapping function. This will be an identity mapping: the output sequence is the same as the input sequence, unless the dynamic type checking reveals an error.
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evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate as an Item.- Overrides:
evaluateItem
in classExpression
- 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
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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process
public void process(XPathContext context) throws XPathException
Process the instruction, without returning any tail calls- Overrides:
process
in classExpression
- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
- if a dynamic error occurs
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copy
public Expression copy()
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression- Overrides:
getItemType
in classUnaryExpression
- Parameters:
th
- the type hierarchy cache- Returns:
- the item type of the items in the result sequence, insofar as this is known statically.
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equals
public boolean equals(java.lang.Object other)
Is this expression the same as another expression?- Overrides:
equals
in classUnaryExpression
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hashCode
public int hashCode()
get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.- Overrides:
hashCode
in classUnaryExpression
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explain
public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Overrides:
explain
in classUnaryExpression
- Parameters:
out
- the expression presenter used to display the structure
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getExpressionName
public java.lang.String getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionName
in classExpression
- Returns:
- a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.
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