Package net.sf.saxon.expr
Class TryCatch
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.TryCatch
- All Implemented Interfaces:
ExportAgent
,Locatable
,IdentityComparable
,Traceable
This class implements a try/catch expression. It consists of a try expression, and a sequence of Nametest/Catch
expression pairs. If the try expression succeeds, its result is returned; otherwise the error code of the
exception is matched against each of the Nametests in turn, and the first matching catch expression is
evaluated.
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Nested Class Summary
Nested Classes -
Field Summary
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 -
Method Summary
Modifier and TypeMethodDescriptionvoid
addCatchExpression
(QNameTest test, Expression catchExpr) boolean
Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself.protected int
Determine the cardinality of the function.protected int
Hashcode supporting equals()copy
(RebindingMap rebindings) Copy an expression.boolean
Is this expression the same as another expression?Evaluate as a singleton itemvoid
Diagnostic print of expression structure.Get the list of catch clausesMake an elaborator for this expressionGet a name identifying the kind of expression, in terms meaningful to a user.int
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().Determine the item type of the value returned by the functionGet the (partial) name of a class that supports streaming of this kind of expressionGet the "try" expressionGet the "try" operandboolean
Ask whether this expression is an instruction.boolean
Iterate over the results of the functionoperands()
Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.optimize
(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform optimisation of an expression and its subexpressions.void
process
(Outputter output, XPathContext context) Process the instructionvoid
setRollbackOutput
(boolean rollback) Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, dispatchTailCall, dynamicError, effectiveBooleanValue, evaluateAsString, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, suppressValidation, toPattern, toShortString, toString, typeCheck, typeCheckChildren, typeError, unordered, verifyParentPointers, withLocation
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
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Constructor Details
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TryCatch
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Method Details
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addCatchExpression
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setRollbackOutput
public void setRollbackOutput(boolean rollback) -
isRollbackOutput
public boolean isRollbackOutput() -
getTryOperand
Get the "try" operand- Returns:
- the primary operand to be evaluated
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getTryExpr
Get the "try" expression- Returns:
- the primary expression to be evaluated
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getCatchClauses
Get the list of catch clauses- Returns:
- the list of catch clauses
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isInstruction
public boolean isInstruction()Ask whether this expression is an instruction. In XSLT streamability analysis this is used to distinguish constructs corresponding to XSLT instructions from other constructs, typically XPath expressions.- Overrides:
isInstruction
in classExpression
- Returns:
- true (if this construct exists at all in an XSLT environment, then it represents an instruction)
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allowExtractingCommonSubexpressions
public boolean allowExtractingCommonSubexpressions()Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself. The result is irrelevant in the case of operands evaluated with a different focus, which will never be extracted in this way, even if they have no focus dependency.- Overrides:
allowExtractingCommonSubexpressions
in classExpression
- Returns:
- false for this kind of expression
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computeCardinality
protected int computeCardinality()Determine the cardinality of the function.- Specified by:
computeCardinality
in classExpression
- 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_ZERO
if the result is known to be an empty sequence, orStaticProperty.ALLOWS_MANY
if if is known to return a sequence of length two or more.
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getItemType
Determine the item type of the value returned by the function- Specified by:
getItemType
in classExpression
- Returns:
- a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)
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operands
Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.- Overrides:
operands
in classExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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optimize
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException Description copied from class:Expression
Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.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.
- Overrides:
optimize
in classExpression
- 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:
getImplementationMethod
in classExpression
- Returns:
- the implementation method, for example
Expression.ITERATE_METHOD
orExpression.EVALUATE_METHOD
orExpression.PROCESS_METHOD
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equals
Is this expression the same as another expression?- Overrides:
equals
in classExpression
- Parameters:
other
- the expression to be compared with this one- Returns:
- true if the two expressions are statically equivalent
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computeHashCode
protected int computeHashCode()Hashcode supporting equals()- Overrides:
computeHashCode
in classExpression
- Returns:
- a computed hash code
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copy
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Parameters:
rebindings
- variables that need to be re-bound- Returns:
- the copy of the original expression
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evaluateItem
Evaluate as a singleton item- Overrides:
evaluateItem
in classExpression
- Parameters:
c
- the dynamic XPath evaluation context- 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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iterate
Iterate over the results of the function- Overrides:
iterate
in classExpression
- Parameters:
c
- 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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process
Description copied from class:Expression
Process the instruction- Overrides:
process
in classExpression
- Parameters:
output
- the destination for the resultcontext
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
- if a dynamic error occurs
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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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export
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
export
in interfaceExportAgent
- Specified by:
export
in classExpression
- 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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getElaborator
Make an elaborator for this expression- Overrides:
getElaborator
in classExpression
- Returns:
- an appropriate
Elaborator
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getStreamerName
Get the (partial) name of a class that supports streaming of this kind of expression- Overrides:
getStreamerName
in classExpression
- Returns:
- the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class
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