net.sf.saxon.expr
Class ItemChecker

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.UnaryExpression
          net.sf.saxon.expr.ItemChecker

All Implemented Interfaces:

Serializable, SourceLocator, Container, EvaluableItem, SequenceIterable, InstructionInfoProvider

public final class ItemChecker
extends UnaryExpression

A ItemChecker implements the item type checking of "treat as": that is, it returns the supplied sequence, checking that all its items are of the correct type

See Also:

Serialized Form

Field Summary

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

ItemChecker(Expression sequence, ItemType itemType, RoleLocator role)
Constructor

Method Summary

boolean	equals(Object other) Is this expression the same as another expression?
Item	evaluateItem(XPathContext context) Evaluate as an Item.
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType(TypeHierarchy th) Determine the data type of the items returned by the expression
ItemType	getRequiredType() Get the required type
RoleLocator	getRoleLocator() Get the RoleLocator (used to construct error messages)
SequenceIterator	iterate(XPathContext context) Iterate over the sequence of values
void	process(XPathContext context) Process the instruction, without returning any tail calls
Expression	simplify(StaticContext env) Simplify an expression
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression

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

computeCardinality, computeSpecialProperties, display, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression

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

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

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ItemChecker

public ItemChecker(Expression sequence,
                   ItemType itemType,
                   RoleLocator role)

Constructor

Method Detail

getRequiredType

public ItemType getRequiredType()

Get the required type

getRoleLocator

public RoleLocator getRoleLocator()

Get the RoleLocator (used to construct error messages)

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Simplify an expression

Overrides:

simplify in class UnaryExpression

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Type-check the expression

Overrides:

typeCheck in class UnaryExpression

Parameters:

env - the static context of the expression

contextItemType - 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 to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

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

XPathException

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. This implementation provides both iterate() and process() methods natively.

Overrides:

getImplementationMethod in class Expression

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Iterate over the sequence of values

Specified by:

iterate in interface SequenceIterable

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

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate as an Item.

Specified by:

evaluateItem in interface EvaluableItem

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

process

public void process(XPathContext context)
             throws XPathException

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

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the items returned by the expression

Overrides:

getItemType in class UnaryExpression

Parameters:

th -

Returns:

the item type of the items in the result sequence, insofar as this is known statically.

equals

public boolean equals(Object other)

Is this expression the same as another expression?

Overrides:

equals in class UnaryExpression