net.sf.saxon.functions

Class Trace

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.FunctionCall

net.sf.saxon.functions.SystemFunctionCall

net.sf.saxon.functions.Trace

All Implemented Interfaces:

SourceLocator, Callable, IdentityComparable, InstructionInfo

public class Trace
extends SystemFunctionCall
implements Callable

This class supports the XPath 2.0 function trace(). The value is traced to the registered output stream (defaulting to System.err), unless a TraceListener is in use, in which case the information is sent to the TraceListener

Field Summary

Fields inherited from class net.sf.saxon.functions.SystemFunctionCall

operation

Fields inherited from class net.sf.saxon.expr.FunctionCall

argument

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
Trace()

Method Summary

Methods

Modifier and Type	Method and Description
Sequence	call(XPathContext context, Sequence[] arguments) Evaluate the expression
int	computeCardinality() Get the static cardinality
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Item	evaluateItem(XPathContext context) Evaluate the function
TraceAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
SequenceIterator	iterate(XPathContext context) Iterate over the results of the function
void	notifyListener(String label, Sequence val, XPathContext context)
Expression	preEvaluate(ExpressionVisitor visitor) preEvaluate: this method suppresses compile-time evaluation by doing nothing
static void	traceItem(Item val, String label, Logger out)

Methods inherited from class net.sf.saxon.functions.SystemFunctionCall

addContextDocumentArgument, addDocToPathMap, bindStaticContext, checkArguments, copy, equalOrNull, equals, getContextNode, getConvertingCallable, getDefaultArgumentNode, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getImplementationMethod, getItemType, getOperation, getRequiredType, makeSystemFunction, operands, optimize, setDetails, toShortString, useContextItemAsDefault

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

addExternalFunctionCallToPathMap, checkArgumentCount, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, promote, replaceOperand, setArguments, setFunctionName, simplifyArguments, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getConfiguration, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExpressionCompiler, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLocationId, getObjectName, getPosture, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamability, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, setPostureAndSweep, simplify, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, typeError, unordered

Methods inherited from class java.lang.Object

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

Constructor Detail

Trace

public Trace()

Method Detail

preEvaluate

public Expression preEvaluate(ExpressionVisitor visitor)

preEvaluate: this method suppresses compile-time evaluation by doing nothing

Overrides:

preEvaluate in class FunctionCall

Parameters:

visitor - an expression visitor

Returns:

the result of the early evaluation, or the original expression, or potentially a simplified expression

computeSpecialProperties

public int computeSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-significant. 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:

computeSpecialProperties in class SystemFunctionCall

Returns:

the special properties, as a bit-significant integer

computeCardinality

public int computeCardinality()

Get the static cardinality

Overrides:

computeCardinality in class SystemFunctionCall

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

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the function

Overrides:

evaluateItem in class Expression

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

notifyListener

public void notifyListener(String label,
                  Sequence val,
                  XPathContext context)

traceItem

public static void traceItem(Item val,
             String label,
             Logger out)

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Iterate over the results of the function

Overrides:

iterate in class Expression

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

call

public Sequence call(XPathContext context,
            Sequence[] arguments)
              throws XPathException

Evaluate the expression

Specified by:

call in interface Callable

Parameters:

context - the dynamic evaluation context

arguments - the values of the arguments, supplied as SequenceIterators

Returns:

the result of the evaluation, in the form of a SequenceIterator

Throws:

XPathException - if a dynamic error occurs during the evaluation of the expression

getStreamingAdjunct

public TraceAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class Expression

Returns:

the relevant StreamingAdjunct, or null if none is available