Class Trace

java.lang.Object

net.sf.saxon.expr.ComputedExpression

net.sf.saxon.expr.FunctionCall

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.Trace

All Implemented Interfaces:

Serializable, SourceLocator, Container, Expression, InstructionInfoProvider

public class Trace
extends SystemFunction

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

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
class	Trace.TracingIterator	Tracing Iterator class

Field Summary

Fields

Modifier and Type	Field	Description
(package private) NamespaceResolver	resolver

Fields inherited from class SystemFunction

operation

Fields inherited from class FunctionCall

argument

Fields inherited from class ComputedExpression

locationId, staticProperties

Fields inherited from interface Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Constructors

Constructor	Description
Trace()

Method Summary

Modifier and Type	Method	Description
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
SequenceIterator	iterate(XPathContext context)	Iterate over the results of the function
Expression	preEvaluate(StaticContext env)	preEvaluate: this method suppresses compile-time evaluation by doing nothing
Expression	simplify(StaticContext env)	Simplify the function call.

Methods inherited from class SystemFunction

addContextDocumentArgument, checkArguments, display, getDetails, getErrorCodeForTypeErrors, getItemType, getRequiredType, main, makeSystemFunction, setDetails, useContextItemAsDefault

Methods inherited from class FunctionCall

checkArgumentCount, getArguments, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, optimize, promote, replaceSubExpression, setArguments, setFunctionNameCode, simplifyArguments, typeCheck

Methods inherited from class ComputedExpression

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

resolver

NamespaceResolver resolver

Constructor Details

Trace

public Trace()

Method Details

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Simplify the function call. This implementation saves the static namespace context, in case it is needed by the TraceListener.

Specified by:

simplify in interface Expression

Overrides:

simplify in class FunctionCall

Parameters:

env - the static context

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

preEvaluate

public Expression preEvaluate(StaticContext env)

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

Overrides:

preEvaluate in class FunctionCall

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 SystemFunction

computeCardinality

public int computeCardinality()

Get the static cardinality

Overrides:

computeCardinality in class SystemFunction

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the function

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

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

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Iterate over the results of the function

Specified by:

iterate in interface Expression

Overrides:

iterate in class ComputedExpression

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