Class TraceExpression
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.instruct.Instruction
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- net.sf.saxon.expr.instruct.TraceExpression
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,TailCallReturner
,InstructionInfo
,org.xml.sax.Locator
public class TraceExpression extends Instruction implements InstructionInfo
A wrapper expression used to trace expressions in XPath and XQuery.- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description (package private) Expression
child
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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 TraceExpression(Expression child)
Create a trace expression that traces execution of a given child expression
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
checkForUpdatingSubexpressions()
Check to ensure that this expression does not contain any inappropriate updating subexpressions.int
computeDependencies()
Get the static properties of this expression (other than its type).Expression
copy()
Copy an expression.boolean
createsNewNodes()
Determine whether this instruction creates new nodes.Item
evaluateItem(XPathContext context)
Evaluate an expression as a single item.void
evaluatePendingUpdates(XPathContext context, PendingUpdateList pul)
Evaluate an updating expression, adding the results to a Pending Update List.void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.int
getCardinality()
Determine the static cardinality of the expression.Expression
getChildExpression()
int
getColumnNumber(long locationId)
Get the column number within the document, entity, or module containing a particular locationint
getConstructType()
Get the construct type.int
getDependencies()
Determine which aspects of the context the expression depends on.int
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().InstructionInfo
getInstructionInfo()
Get the InstructionInfo details about the construct.int
getInstructionNameCode()
Get the namecode of the instruction for use in diagnosticsItemType
getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instructionint
getLineNumber(long locationId)
Get the line number of the expression being traced.NamespaceResolver
getNamespaceResolver()
Get the namespace resolver to supply the namespace context of the instruction that is being tracedStructuredQName
getObjectName()
Get a name identifying the object of the expression, for example a function name, template name, variable name, key name, element name, etc.java.util.Iterator<java.lang.String>
getProperties()
Get an iterator over all the properties available.java.lang.Object
getProperty(java.lang.String name)
Get a named property of the instruction/expressionjava.lang.String
getSystemId(long locationId)
Get the system identifier (that is the base URI) of the static context of the expression being traced.boolean
isUpdatingExpression()
Determine whether this is an updating expression as defined in the XQuery update specificationboolean
isVacuousExpression()
Determine whether this is a vacuous expression as defined in the XQuery update specificationSequenceIterator<Item>
iterate(XPathContext context)
Return an Iterator to iterate over the values of a sequence.java.util.Iterator<Expression>
iterateSubExpressions()
Get the immediate sub-expressions of this expression.Expression
optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions.TailCall
processLeavingTail(XPathContext context)
Execute this instruction, with the possibility of returning tail calls if there are any.Expression
promote(PromotionOffer offer, Expression parent)
Offer promotion for this subexpression.boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionvoid
setConstructType(int type)
Set the type of construct.void
setNamespaceResolver(NamespaceResolver resolver)
Set the namespace context for the instruction being traced.void
setObjectName(StructuredQName qName)
Set a name identifying the object of the expression, for example a function name, template name, variable name, key name, element name, etc.void
setProperty(java.lang.String name, java.lang.Object value)
Set a named property of the instruction/expressionExpression
simplify(ExpressionVisitor visitor)
Simplify an expression.Expression
typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Perform type checking of an expression and its subexpressions.-
Methods inherited from class net.sf.saxon.expr.instruct.Instruction
assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, getExpressionName, getInstructionName, getIteratorFromProcessMethod, getSourceLocator, isXSLT, process, promoteInst
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkPermittedContents, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, explain, getColumnNumber, getContainer, getEvaluationMethod, getExecutable, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods inherited from interface net.sf.saxon.trace.InstructionInfo
getLineNumber, getSystemId
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Field Detail
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child
Expression child
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Constructor Detail
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TraceExpression
public TraceExpression(Expression child)
Create a trace expression that traces execution of a given child expression- Parameters:
child
- the expression to be traced. This will be available to the TraceListener as the value of the "expression" property of the InstructionInfo.
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Method Detail
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setConstructType
public void setConstructType(int type)
Set the type of construct. This will generally be a constant in classLocation
- Parameters:
type
- an integer code for the type of construct being traced
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getConstructType
public int getConstructType()
Get the construct type. This will generally be a constant in classLocation
- Specified by:
getConstructType
in interfaceInstructionInfo
- Overrides:
getConstructType
in classInstruction
- Returns:
- the type of expression, as enumerated in class
Location
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setNamespaceResolver
public void setNamespaceResolver(NamespaceResolver resolver)
Set the namespace context for the instruction being traced. This is needed if the tracelistener wants to evaluate XPath expressions in the context of the current instruction- Parameters:
resolver
- The namespace resolver, or null if none is needed
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getNamespaceResolver
public NamespaceResolver getNamespaceResolver()
Get the namespace resolver to supply the namespace context of the instruction that is being traced- Returns:
- the namespace resolver, or null if none is in use
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setObjectName
public void setObjectName(StructuredQName qName)
Set a name identifying the object of the expression, for example a function name, template name, variable name, key name, element name, etc. This is used only where the name is known statically.- Parameters:
qName
- the name of the object, or null if not applicable
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getObjectName
public StructuredQName getObjectName()
Get a name identifying the object of the expression, for example a function name, template name, variable name, key name, element name, etc. This is used only where the name is known statically.- Specified by:
getObjectName
in interfaceInstructionInfo
- Overrides:
getObjectName
in classExpression
- Returns:
- the name of the object, or null if not applicable
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setProperty
public void setProperty(java.lang.String name, java.lang.Object value)
Set a named property of the instruction/expression- Parameters:
name
- the name of the propertyvalue
- the value of the property
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getProperty
public java.lang.Object getProperty(java.lang.String name)
Get a named property of the instruction/expression- Specified by:
getProperty
in interfaceInstructionInfo
- Overrides:
getProperty
in classExpression
- Parameters:
name
- the name of the property- Returns:
- the value of the property
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getProperties
public java.util.Iterator<java.lang.String> getProperties()
Get an iterator over all the properties available. The values returned by the iterator will be of type String, and each string can be supplied as input to the getProperty() method to retrieve the value of the property.- Specified by:
getProperties
in interfaceInstructionInfo
- Overrides:
getProperties
in classExpression
- Returns:
- an iterator over the properties.
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getInstructionInfo
public InstructionInfo getInstructionInfo()
Get the InstructionInfo details about the construct. This is to satisfy the InstructionInfoProvider interface.- Returns:
- the instruction details
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getSystemId
public java.lang.String getSystemId(long locationId)
Get the system identifier (that is the base URI) of the static context of the expression being traced. This returns the same result as getSystemId(), it is provided to satisfy theLocationProvider
interface.- Specified by:
getSystemId
in interfaceLocationProvider
- Overrides:
getSystemId
in classExpression
- Parameters:
locationId
- not used- Returns:
- the URI of the module containing the expression
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getLineNumber
public int getLineNumber(long locationId)
Get the line number of the expression being traced. This returns the same result as getLineNumber(), it is provided to satisfy theLocationProvider
interface.- Specified by:
getLineNumber
in interfaceLocationProvider
- Overrides:
getLineNumber
in classExpression
- Parameters:
locationId
- not used- Returns:
- the line number of the expression within its module
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getColumnNumber
public int getColumnNumber(long locationId)
Description copied from interface:LocationProvider
Get the column number within the document, entity, or module containing a particular location- Specified by:
getColumnNumber
in interfaceLocationProvider
- Overrides:
getColumnNumber
in classExpression
- Parameters:
locationId
- identifier of the location in question (as passed down the Receiver pipeline)- Returns:
- the column number within the document, entity, or module, or -1 if this is not available
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copy
public Expression copy()
Description copied from class:Expression
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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isUpdatingExpression
public boolean isUpdatingExpression()
Determine whether this is an updating expression as defined in the XQuery update specification- Overrides:
isUpdatingExpression
in classExpression
- Returns:
- true if this is an updating expression
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isVacuousExpression
public boolean isVacuousExpression()
Determine whether this is a vacuous expression as defined in the XQuery update specification- Overrides:
isVacuousExpression
in classExpression
- Returns:
- true if this expression is vacuous
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checkForUpdatingSubexpressions
public void checkForUpdatingSubexpressions() throws XPathException
Check to ensure that this expression does not contain any inappropriate updating subexpressions. This check is overridden for those expressions that permit updating subexpressions.- Overrides:
checkForUpdatingSubexpressions
in classExpression
- Throws:
XPathException
- if the expression has a non-permitted updating subexpression
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simplify
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.- Specified by:
simplify
in classInstruction
- 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
Description copied from class:Expression
Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.
If the implementation returns a value other than "this", then it is required to ensure that the location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.
- Overrides:
typeCheck
in classExpression
- 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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optimize
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) 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 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 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()
Description copied from class:Instruction
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is prefered. For instructions this is the process() method.- Overrides:
getImplementationMethod
in classInstruction
- Returns:
- the implementation method, for example
Expression.ITERATE_METHOD
orExpression.EVALUATE_METHOD
orExpression.PROCESS_METHOD
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promote
public Expression promote(PromotionOffer offer, Expression parent) throws XPathException
Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. This method is always called at compile time.- Overrides:
promote
in classInstruction
- Parameters:
offer
- details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expressionparent
- the parent of the subexpression- Returns:
- if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
- Throws:
XPathException
- if any error is detected
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processLeavingTail
public TailCall processLeavingTail(XPathContext context) throws XPathException
Execute this instruction, with the possibility of returning tail calls if there are any. This outputs the trace information via the registered TraceListener, and invokes the instruction being traced.- Specified by:
processLeavingTail
in interfaceTailCallReturner
- Specified by:
processLeavingTail
in classInstruction
- Parameters:
context
- the dynamic execution context- Returns:
- either null, or a tail call that the caller must invoke on return
- Throws:
XPathException
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getItemType
public ItemType getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instruction- Overrides:
getItemType
in classInstruction
- Parameters:
th
- the type hierarchy cache- Returns:
- the static item type of the instruction
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getCardinality
public int getCardinality()
Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.- Overrides:
getCardinality
in classExpression
- Returns:
- one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).
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getDependencies
public int getDependencies()
Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such asStaticProperty.DEPENDS_ON_CONTEXT_ITEM
andStaticProperty.DEPENDS_ON_CURRENT_ITEM
. The default implementation combines the intrinsic dependencies of this expression with the dependencies of the subexpressions, computed recursively. This is overridden for expressions such as FilterExpression where a subexpression's dependencies are not necessarily inherited by the parent expression.- Overrides:
getDependencies
in classExpression
- Returns:
- a set of bit-significant flags identifying the dependencies of the expression
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createsNewNodes
public final boolean createsNewNodes()
Determine whether this instruction creates new nodes.- Overrides:
createsNewNodes
in classInstruction
- Returns:
- true if the instruction creates new nodes (or if it can't be proved that it doesn't)
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computeDependencies
public int computeDependencies()
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:
computeDependencies
in classExpression
- Returns:
- a set of flags indicating static properties of this expression
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evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.- Overrides:
evaluateItem
in classInstruction
- 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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iterate
public SequenceIterator<Item> iterate(XPathContext context) throws XPathException
Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.- Overrides:
iterate
in classInstruction
- 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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iterateSubExpressions
public java.util.Iterator<Expression> iterateSubExpressions()
Description copied from class:Expression
Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.- Overrides:
iterateSubExpressions
in classExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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replaceSubExpression
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression- Overrides:
replaceSubExpression
in classExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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getChildExpression
public Expression getChildExpression()
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getInstructionNameCode
public int getInstructionNameCode()
Description copied from class:Instruction
Get the namecode of the instruction for use in diagnostics- Overrides:
getInstructionNameCode
in classInstruction
- Returns:
- a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace
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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.- Specified by:
explain
in classExpression
- Parameters:
out
- the expression presenter used to display the structure
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evaluatePendingUpdates
public void evaluatePendingUpdates(XPathContext context, PendingUpdateList pul) throws XPathException
Evaluate an updating expression, adding the results to a Pending Update List. The default implementation of this method, which is used for non-updating expressions, throws an UnsupportedOperationException- Overrides:
evaluatePendingUpdates
in classExpression
- Parameters:
context
- the XPath dynamic evaluation contextpul
- the pending update list to which the results should be written- Throws:
XPathException
- if evaluation fails
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