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

public class TryCatch
extends Expression

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.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TryCatch.CatchClause

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

Constructor Summary

Constructors

Constructor and Description
TryCatch(Expression tryExpr)

Method Summary

Modifier and Type	Method and Description
void	addCatchExpression(QNameTest test, Expression catchExpr)
boolean	allowExtractingCommonSubexpressions() Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself.
int	computeCardinality() Determine the cardinality of the function.
int	computeHashCode() Hashcode supporting equals()
Expression	copy(RebindingMap rebindings) Copy an expression.
boolean	equals(java.lang.Object other) Is this expression the same as another expression?
Item	evaluateItem(XPathContext c) Evaluate as a singleton item
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
java.util.List<TryCatch.CatchClause>	getCatchClauses() Get the list of catch clauses
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().
ItemType	getItemType() Determine the item type of the value returned by the function
java.lang.String	getStreamerName() Get the (partial) name of a class that supports streaming of this kind of expression
Expression	getTryExpr() Get the "try" expression
Operand	getTryOperand() Get the "try" operand
boolean	isInstruction() Ask whether this expression is an instruction.
boolean	isRollbackOutput()
SequenceIterator<?>	iterate(XPathContext c) Iterate over the results of the function
java.lang.Iterable<Operand>	operands() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform optimisation of an expression and its subexpressions.
void	process(XPathContext context) Process the instruction, without returning any tail calls
void	setRollbackOutput(boolean rollback)

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toString, typeCheck, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

TryCatch

public TryCatch(Expression tryExpr)

Method Detail

addCatchExpression

public void addCatchExpression(QNameTest test,
                               Expression catchExpr)

setRollbackOutput

public void setRollbackOutput(boolean rollback)

isRollbackOutput

public boolean isRollbackOutput()

getTryOperand

public Operand getTryOperand()

Get the "try" operand

Returns:

the primary operand to be evaluated

getTryExpr

public Expression getTryExpr()

Get the "try" expression

Returns:

the primary expression to be evaluated

getCatchClauses

public java.util.List<TryCatch.CatchClause> getCatchClauses()

Get the list of catch clauses

Returns:

the list of catch clauses

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 class Expression

Returns:

true (if this construct exists at all in an XSLT environment, then it represents an instruction)

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 class Expression

Returns:

false for this kind of expression

computeCardinality

public int computeCardinality()

Determine the cardinality of the function.

Specified by:

computeCardinality in class Expression

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 return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

getItemType

public ItemType getItemType()

Determine the item type of the value returned by the function

Specified by:

getItemType in class Expression

Returns:

a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

operands

public java.lang.Iterable<Operand> 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 class Expression

Returns:

an iterator containing the sub-expressions of this expression

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 class Expression

Parameters:

visitor - an expression visitor

contextInfo - 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

Returns:

the original expression, rewritten if appropriate to optimize execution

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

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 class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

equals

public boolean equals(java.lang.Object other)

Is this expression the same as another expression?

Overrides:

equals in class Expression

Parameters:

other - the expression to be compared with this one

Returns:

true if the two expressions are statically equivalent

computeHashCode

public int computeHashCode()

Hashcode supporting equals()

Overrides:

computeHashCode in class Expression

Returns:

a computed hash code

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings - variables that need to be re-bound

Returns:

the copy of the original expression

evaluateItem

public Item evaluateItem(XPathContext c)
                  throws XPathException

Evaluate as a singleton item

Overrides:

evaluateItem in class Expression

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

iterate

public SequenceIterator<?> iterate(XPathContext c)
                            throws XPathException

Iterate over the results of the function

Overrides:

iterate in class Expression

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

process

public void process(XPathContext context)
             throws XPathException

Description copied from class: Expression

Process the instruction, without returning any tail calls

Overrides:

process in class Expression

Parameters:

context - The dynamic context, giving access to the current node, the current variables, etc.

Throws:

XPathException - if a dynamic error occurs

getExpressionName

public java.lang.String getExpressionName()

Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:

getExpressionName in class Expression

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.

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:

export in interface ExportAgent

Specified by:

export in class Expression

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.

getStreamerName

public java.lang.String getStreamerName()

Get the (partial) name of a class that supports streaming of this kind of expression

Overrides:

getStreamerName in class Expression

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