net.sf.saxon.expr

Class AttributeGetter

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.AttributeGetter

All Implemented Interfaces:

ExportAgent, IdentityComparable

public final class AttributeGetter
extends Expression

An AttributeGetter is an expression that returns the value of a specific attribute of the context item, provided that it is an untyped element node. That is, it represents the expression data(./@name) assuming that all data is untyped.

Field Summary

Fields

Modifier and Type	Field and Description
static int	CHECK_CONTEXT_ITEM_IS_NODE
static int	CHECK_CONTEXT_ITEM_PRESENT

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

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

Constructor Summary

Constructors

Constructor and Description
AttributeGetter(FingerprintedQName attributeName)

Method Summary

Modifier and Type	Method and Description
PathMap.PathMapNodeSet	addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.
int	computeCardinality() Compute the static cardinality of this expression
int	computeHashCode()
AttributeGetter	copy(RebindingMap rebindings) Copy an expression.
boolean	equals(java.lang.Object obj)
Item	evaluateItem(XPathContext context) Evaluate an expression as a single item.
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
FingerprintedQName	getAttributeName()
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().
int	getIntrinsicDependencies() Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions.
ItemType	getItemType() Determine the static item type of the expression, as precisely possible.
int	getRequiredChecks() Ask what run-time checks are needed.
void	setRequiredChecks(int checks) Say what run-time checks are needed.
java.lang.String	toShortString() Produce a short string identifying the expression for use in error messages
java.lang.String	toString() The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.

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

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

Methods inherited from class java.lang.Object

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

Field Detail

CHECK_CONTEXT_ITEM_PRESENT

public static final int CHECK_CONTEXT_ITEM_PRESENT

See Also:

Constant Field Values

CHECK_CONTEXT_ITEM_IS_NODE

public static final int CHECK_CONTEXT_ITEM_IS_NODE

See Also:

Constant Field Values

Constructor Detail

AttributeGetter

public AttributeGetter(FingerprintedQName attributeName)

Method Detail

getAttributeName

public FingerprintedQName getAttributeName()

setRequiredChecks

public void setRequiredChecks(int checks)

Say what run-time checks are needed. (This information is only used when generating bytecode)

Parameters:

checks - the run-time checks that need to be performed

getRequiredChecks

public int getRequiredChecks()

Ask what run-time checks are needed. (This information is only used when generating bytecode)

Returns:

the run-time checks that need to be performed

getItemType

public ItemType getItemType()

Description copied from class: Expression

Determine the static item type of the expression, as precisely possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method should always return a result, though it may be the best approximation that is available at the time.

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)

computeCardinality

public int computeCardinality()

Description copied from class: Expression

Compute the static cardinality of this expression

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

getIntrinsicDependencies

public int getIntrinsicDependencies()

Description copied from class: Expression

Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".

Overrides:

getIntrinsicDependencies in class Expression

Returns:

a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

copy

public AttributeGetter copy(RebindingMap rebindings)

Description copied from class: Expression

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings - a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.

Returns:

the copy of the original expression

addToPathMap

public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)

Description copied from class: Expression

Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Overrides:

addToPathMap in class Expression

Parameters:

pathMap - the PathMap to which the expression should be added

pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added

Returns:

the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

getImplementationMethod

public int getImplementationMethod()

Description copied from class: Expression

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

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Description copied from class: Expression

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 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

getExpressionName

public java.lang.String getExpressionName()

Description copied from class: Expression

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 export() output displaying the expression.

toShortString

public java.lang.String toShortString()

Description copied from class: Expression

Produce a short string identifying the expression for use in error messages

Overrides:

toShortString in class Expression

Returns:

a short string, sufficient to identify the expression

toString

public java.lang.String toString()

Description copied from class: Expression

The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.

For subclasses of Expression that represent XPath expressions, the result should always be a string that parses as an XPath 3.0 expression. The expression produced should be equivalent to the original making certain assumptions about the static context. In general the expansion will make no assumptions about namespace bindings, except that (a) the prefix "xs" is used to refer to the XML Schema namespace, and (b) the default function namespace is assumed to be the "fn" namespace.

In the case of XSLT instructions and XQuery expressions, the toString() method gives an abstracted view of the syntax that is not designed in general to be parseable.

Overrides:

toString in class Expression

Returns:

a representation of the expression as a string

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

computeHashCode

public int computeHashCode()

Overrides:

computeHashCode in class Expression

export

public void export(ExpressionPresenter out)
            throws XPathException

Description copied from class: Expression

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.