Package net.sf.saxon.expr
Class CastableExpression
- 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.CastingExpression
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- net.sf.saxon.expr.CastableExpression
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- All Implemented Interfaces:
ExportAgent,Locatable,IdentityComparable,Traceable
public final class CastableExpression extends CastingExpression
Castable Expression: implements "Expr castable as atomic-type?". The implementation simply wraps a cast expression with a try/catch.
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Field Summary
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Fields inherited from class net.sf.saxon.expr.CastingExpression
converter
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Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD
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Constructor Summary
Constructors Constructor Description CastableExpression(Expression source, AtomicType target, boolean allowEmpty)Create a "castable" expression of the form "source castable as target"
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description intcomputeCardinality()Determine the static cardinality.intcomputeHashCode()get HashCode for comparing two expressions.Expressioncopy(RebindingMap rebindings)Copy an expression.booleaneffectiveBooleanValue(XPathContext context)Get the effective boolean value of the expression.booleanequals(java.lang.Object other)Is this expression the same as another expression?BooleanValueevaluateItem(XPathContext context)Evaluate the expressionvoidexport(ExpressionPresenter out)Diagnostic print of expression structure.java.lang.StringgetExpressionName()Get a name identifying the kind of expression, in terms meaningful to a user.intgetImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().ItemTypegetItemType()Determine the data type of the result of the Castable expressionUTypegetStaticUType(UType contextItemType)Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.Expressionoptimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Optimize the expressionprotected ExpressionpreEvaluate()java.lang.StringtoString()The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.ExpressiontypeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Type-check the expression-
Methods inherited from class net.sf.saxon.expr.CastingExpression
allowsEmpty, computeSpecialProperties, export, getConverter, getIntrinsicDependencies, getNamespaceResolver, getOperandRole, getTargetPrimitiveType, getTargetType, isOperandIsStringLiteral, setAllowEmpty, setOperandIsStringLiteral, setTargetType, simplify
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Methods inherited from class net.sf.saxon.expr.UnaryExpression
displayOperator, emitExtraAttributes, getBaseExpression, getOperand, operands, setBaseExpression, toShortString
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
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Constructor Detail
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CastableExpression
public CastableExpression(Expression source, AtomicType target, boolean allowEmpty)
Create a "castable" expression of the form "source castable as target"- Parameters:
source- The source expressiontarget- The type being tested againstallowEmpty- true if an empty sequence is acceptable, that is if the expression was written as "source castable as target?"
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Method Detail
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
Type-check the expression- Overrides:
typeCheckin classUnaryExpression- Parameters:
visitor- an expression visitorcontextInfo- Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.- 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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preEvaluate
protected Expression preEvaluate() throws XPathException
- Throws:
XPathException
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optimize
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
Optimize the expression- Overrides:
optimizein classUnaryExpression- Parameters:
visitor- an expression visitorcontextInfo- 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
- 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 directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.- Specified by:
getImplementationMethodin classExpression- Returns:
- the implementation method, for example
Expression.ITERATE_METHODorExpression.EVALUATE_METHODorExpression.PROCESS_METHOD
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equals
public boolean equals(java.lang.Object other)
Is this expression the same as another expression?- Overrides:
equalsin classUnaryExpression- Parameters:
other- the other operand; the result is false if this is not an Expression- Returns:
- true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.
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computeHashCode
public int computeHashCode()
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:
computeHashCodein classUnaryExpression- Returns:
- a computed hash code
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getItemType
public ItemType getItemType()
Determine the data type of the result of the Castable expression- Overrides:
getItemTypein classUnaryExpression- Returns:
- the item type of the items in the result sequence, insofar as this is known statically.
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getStaticUType
public UType getStaticUType(UType contextItemType)
Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.- Overrides:
getStaticUTypein classExpression- Parameters:
contextItemType-- Returns:
- the static item type of the expression according to the XSLT 3.0 defined rules
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computeCardinality
public int computeCardinality()
Description copied from class:UnaryExpressionDetermine the static cardinality. Default implementation returns the cardinality of the operand- Overrides:
computeCardinalityin classUnaryExpression- Returns:
- the computed cardinality, as one of the values
StaticProperty.ALLOWS_ZERO_OR_ONE,StaticProperty.EXACTLY_ONE,StaticProperty.ALLOWS_ONE_OR_MORE,StaticProperty.ALLOWS_ZERO_OR_MORE. May also returnStaticProperty.ALLOWS_ZEROif the result is known to be an empty sequence, orStaticProperty.ALLOWS_MANYif if is known to return a sequence of length two or more.
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copy
public Expression copy(RebindingMap rebindings)
Description copied from class:ExpressionCopy an expression. This makes a deep copy.- Specified by:
copyin classExpression- Parameters:
rebindings- a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.- Returns:
- the copy of the original expression
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evaluateItem
public BooleanValue evaluateItem(XPathContext context) throws XPathException
Evaluate the expression- Overrides:
evaluateItemin 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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effectiveBooleanValue
public boolean effectiveBooleanValue(XPathContext context) throws XPathException
Description copied from class:ExpressionGet the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.- Overrides:
effectiveBooleanValuein classExpression- Parameters:
context- The context in which the expression is to be evaluated- Returns:
- the effective boolean value
- Throws:
XPathException- if any dynamic error occurs evaluating the expression
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getExpressionName
public java.lang.String getExpressionName()
Description copied from class:ExpressionGet a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionNamein 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 export() output displaying the expression.
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toString
public java.lang.String toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax- Overrides:
toStringin classUnaryExpression- Returns:
- a representation of the expression as a string
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export
public void export(ExpressionPresenter out) throws XPathException
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
exportin interfaceExportAgent- Overrides:
exportin classUnaryExpression- Parameters:
out- the expression presenter used to display the structure- Throws:
XPathException- if the export fails, for example if an expression is found that won't work in the target environment.
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