net.sf.saxon.value

Class AtomicValue

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.value.AtomicValue

All Implemented Interfaces:

Iterable<AtomicValue>, PullEvent, AtomicSequence, GroundedValue, IdentityComparable, Item, Sequence, ConversionResult

Direct Known Subclasses:

Base64BinaryValue, BooleanValue, CalendarValue, DurationValue, HexBinaryValue, NestedIntegerValue, NumericValue, QualifiedNameValue, StringValue

public abstract class AtomicValue
extends AbstractItem
implements AtomicSequence, ConversionResult, IdentityComparable

The AtomicValue class corresponds to the concept of an atomic value in the XPath 2.0 data model. Atomic values belong to one of the 19 primitive types defined in XML Schema; or they are of type xs:untypedAtomic; or they are "external objects", representing a Saxon extension to the XPath 2.0 type system.

The AtomicValue class contains some methods that are suitable for applications to use, and many others that are designed for internal use by Saxon itself. These have not been fully classified. At present, therefore, none of the methods on this class should be considered to be part of the public Saxon API.

Author:

Michael H. Kay

Field Summary

Fields

Modifier and Type	Field and Description
static AtomicMatchKey	NaN_MATCH_KEY A match key for use in situations where NaN = NaN
protected AtomicType	typeLabel

Constructor Summary

Constructors

Constructor and Description
AtomicValue()

Method Summary

Methods

Modifier and Type	Method and Description
AtomicValue	asAtomic() Calling this method on a ConversionResult returns the AtomicValue that results from the conversion if the conversion was successful, and throws a ValidationException explaining the conversion error otherwise.
AtomicMatchKey	asMapKey() Get a value whose equals() method follows the "same key" rules for comparing the keys of a map.
AtomicSequence	atomize() Atomize the item.
void	checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) Check statically that the results of the expression are capable of constructing the content of a given schema type.
abstract AtomicValue	copyAsSubType(AtomicType typeLabel) Create a copy of this atomic value, with a different type label
boolean	effectiveBooleanValue() Get the effective boolean value of the value
abstract boolean	equals(Object o) The equals() methods on atomic values is defined to follow the semantics of eq when applied to two atomic values.
CharSequence	getCanonicalLexicalRepresentation() Get the canonical lexical representation as defined in XML Schema.
int	getCardinality() Determine the static cardinality
AtomicValue	getComponent(AccessorFn.Component component) Method to extract components of a value.
AtomicType	getItemType() Determine the data type of the value
protected abstract CharSequence	getPrimitiveStringValue() Convert the value to a string, using the serialization rules for the primitive type.
abstract BuiltInAtomicType	getPrimitiveType() Determine the primitive type of the value.
abstract Comparable	getSchemaComparable() Get a Comparable value that implements the XML Schema ordering comparison semantics for this value.
String	getStringValue() Convert the value to a string, using the serialization rules.
CharSequence	getStringValueCS() Get the value of the item as a CharSequence.
UType	getUType() Determine the UType of the value.
abstract AtomicMatchKey	getXPathComparable(boolean ordered, StringCollator collator, int implicitTimezone) Get an object value that implements the XPath equality and ordering comparison semantics for this value.
AtomicValue	head() To implement Sequence, this method returns the item itself
int	identityHashCode() Get a hashCode that offers the guarantee that if A.isIdentical(B), then A.identityHashCode() == B.identityHashCode()
boolean	isIdentical(AtomicValue v) Determine whether two atomic values are identical, as determined by XML Schema rules.
boolean	isIdentical(IdentityComparable other) Determine whether two IdentityComparable objects are identical.
boolean	isNaN() Test whether the value is the special value NaN
AtomicValue	itemAt(int n) Get the n'th item in the sequence (starting from 0).
AtomicIterator	iterate() To implement Sequence, this method returns a singleton iterator that delivers this item in the form of a sequence
Iterator<AtomicValue>	iterator() Returns a Java iterator over the atomic sequence.
void	process(XPathContext context) Process the instruction, without returning any tail calls
void	setTypeLabel(AtomicType type) Set the type label on this atomic value.
String	toString() Get string value.

Methods inherited from class net.sf.saxon.om.AbstractItem

getLength, reduce, subsequence

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.om.AtomicSequence

getLength

Methods inherited from interface net.sf.saxon.om.GroundedValue

reduce, subsequence

Field Detail

typeLabel

protected AtomicType typeLabel

NaN_MATCH_KEY

public static final AtomicMatchKey NaN_MATCH_KEY

A match key for use in situations where NaN = NaN

Constructor Detail

AtomicValue

public AtomicValue()

Method Detail

atomize

public AtomicSequence atomize()
                       throws XPathException

Atomize the item.

Specified by:

atomize in interface Item

Returns:

the result of atomization

Throws:

XPathException - if atomization is not allowed for this kind of item

head

public final AtomicValue head()

To implement Sequence, this method returns the item itself

Specified by:

head in interface AtomicSequence

Specified by:

head in interface GroundedValue

Specified by:

head in interface Item

Specified by:

head in interface Sequence

Overrides:

head in class AbstractItem

Returns:

this item

iterate

public final AtomicIterator iterate()

To implement Sequence, this method returns a singleton iterator that delivers this item in the form of a sequence

Specified by:

iterate in interface AtomicSequence

Specified by:

iterate in interface GroundedValue

Specified by:

iterate in interface Sequence

Overrides:

iterate in class AbstractItem

Returns:

a singleton iterator that returns this item

setTypeLabel

public void setTypeLabel(AtomicType type)

Set the type label on this atomic value. Note that this modifies the value, so it must only called if the caller is confident that the value is not shared. In other cases, use copyAsSubType(net.sf.saxon.type.AtomicType)

Parameters:

type - the type label to be set

getSchemaComparable

public abstract Comparable getSchemaComparable()

Get a Comparable value that implements the XML Schema ordering comparison semantics for this value. An implementation must be provided for all atomic types.

In the case of data types that are partially ordered, the returned Comparable extends the standard semantics of the compareTo() method by returning the value SequenceTool.INDETERMINATE_ORDERING when there is no defined order relationship between two given values. This value is also returned when two values of different types are compared.

Specified by:

getSchemaComparable in interface AtomicSequence

Returns:

a Comparable that follows XML Schema comparison rules

getXPathComparable

public abstract AtomicMatchKey getXPathComparable(boolean ordered,
                                StringCollator collator,
                                int implicitTimezone)
                                           throws NoDynamicContextException

Get an object value that implements the XPath equality and ordering comparison semantics for this value. If the ordered parameter is set to true, the result will be a Comparable and will support a compareTo() method with the semantics of the XPath lt/gt operator, provided that the other operand is also obtained using the getXPathComparable() method. In all cases the result will support equals() and hashCode() methods that support the semantics of the XPath eq operator, again provided that the other operand is also obtained using the getXPathComparable() method. A collation is supplied for comparing strings, and an implicit timezone for comparing date/time values that have no saved timezone.

Parameters:

ordered - true if an ordered comparison is required. In this case the result is null if the type is unordered; in other cases the returned value will be a Comparable.

collator - the collation to be used when comparing strings

implicitTimezone - the implicit timezone in the dynamic context, used when comparing dates/times with and without timezone

Returns:

an Object whose equals() and hashCode() methods implement the XPath comparison semantics with respect to this atomic value. If ordered is specified, the result will either be null if no ordering is defined, or will be a Comparable

Throws:

NoDynamicContextException - if the supplied implicit timezone is "NO_TIMEZONE" (meaning unknown), and the implicit timezone is actually required because the value in question is a date/time value with no timezone. This can cause a failure to evaluate expressions statically (because the implicit timezone is not known statically), and it will then be caught, meaning that the expression has to be evaluated dynamically.

asMapKey

public AtomicMatchKey asMapKey()

Get a value whose equals() method follows the "same key" rules for comparing the keys of a map.

Returns:

a value with the property that the equals() and hashCode() methods follow the rules for comparing keys in maps.

equals

public abstract boolean equals(Object o)

The equals() methods on atomic values is defined to follow the semantics of eq when applied to two atomic values. When the other operand is not an atomic value, the result is undefined (may be false, may be an exception). When the other operand is an atomic value that cannot be compared with this one, the method must throw a ClassCastException.

The hashCode() method is consistent with equals().

Overrides:

equals in class Object

Parameters:

o - the other value

Returns:

true if the other operand is an atomic value and the two values are equal as defined by the XPath eq operator

isIdentical

public boolean isIdentical(AtomicValue v)

Determine whether two atomic values are identical, as determined by XML Schema rules. This is a stronger test than equality (even schema-equality); for example two dateTime values are not identical unless they are in the same timezone.

Note that even this check ignores the type annotation of the value. The integer 3 and the short 3 are considered identical, even though they are not fully interchangeable. "Identical" means the same point in the value space, regardless of type annotation.

NaN is identical to itself.

Parameters:

v - the other value to be compared with this one

Returns:

true if the two values are identical, false otherwise.

isIdentical

public boolean isIdentical(IdentityComparable other)

Determine whether two IdentityComparable objects are identical. This is a stronger test than equality (even schema-equality); for example two dateTime values are not identical unless they are in the same timezone.

Specified by:

isIdentical in interface IdentityComparable

Parameters:

other - the value to be compared

Returns:

true if the two values are identical, false otherwise

identityHashCode

public int identityHashCode()

Get a hashCode that offers the guarantee that if A.isIdentical(B), then A.identityHashCode() == B.identityHashCode()

Specified by:

identityHashCode in interface IdentityComparable

Returns:

a hashCode suitable for use when testing for identity.

getStringValueCS

public final CharSequence getStringValueCS()

Get the value of the item as a CharSequence. This is in some cases more efficient than the version of the method that returns a String.

Specified by:

getStringValueCS in interface AtomicSequence

Specified by:

getStringValueCS in interface GroundedValue

Specified by:

getStringValueCS in interface Item

Returns:

the string value of the sequence.

See Also:

Item.getStringValue()

getCanonicalLexicalRepresentation

public CharSequence getCanonicalLexicalRepresentation()

Get the canonical lexical representation as defined in XML Schema. This is not always the same as the result of casting to a string according to the XPath rules.

Specified by:

getCanonicalLexicalRepresentation in interface AtomicSequence

Returns:

the canonical lexical representation if defined in XML Schema; otherwise, the result of casting to string according to the XPath 2.0 rules

process

public void process(XPathContext context)
             throws XPathException

Process the instruction, without returning any tail calls

Parameters:

context - The dynamic context, giving access to the current node, the current variables, etc.

Throws:

XPathException - if the current receiver fails for any reason, for example with a serialization error due to invalid characters in the content

itemAt

public final AtomicValue itemAt(int n)

Get the n'th item in the sequence (starting from 0). This is defined for all Values, but its real benefits come for a sequence Value stored extensionally (or for a MemoClosure, once all the values have been read)

Specified by:

itemAt in interface AtomicSequence

Specified by:

itemAt in interface GroundedValue

Overrides:

itemAt in class AbstractItem

Parameters:

n - position of the required item, counting from zero.

Returns:

the n'th item in the sequence, where the first item in the sequence is numbered zero. If n is negative or >= the length of the sequence, returns null.

getItemType

public final AtomicType getItemType()

Determine the data type of the value

Returns:

the type annotation of the atomic value

getPrimitiveType

public abstract BuiltInAtomicType getPrimitiveType()

Determine the primitive type of the value. This delivers the same answer as getItemType().getPrimitiveItemType(). The primitive types are the 19 primitive types of XML Schema, plus xs:integer, xs:dayTimeDuration and xs:yearMonthDuration, and xs:untypedAtomic. For external objects, the result is xs:anyAtomicType.

Returns:

the primitive type

getUType

public final UType getUType()

Determine the UType of the value. This delivers the same answer as getItemType().getUType()

Returns:

the primitive UType

getCardinality

public final int getCardinality()

Determine the static cardinality

Returns:

code identifying the cardinality

See Also:

Cardinality

copyAsSubType

public abstract AtomicValue copyAsSubType(AtomicType typeLabel)

Create a copy of this atomic value, with a different type label

Parameters:

typeLabel - the type label of the new copy. The caller is responsible for checking that the value actually conforms to this type.

Returns:

the copied value

isNaN

public boolean isNaN()

Test whether the value is the special value NaN

Returns:

true if the value is float NaN or double NaN or precisionDecimal NaN; otherwise false

getStringValue

public final String getStringValue()

Convert the value to a string, using the serialization rules. For atomic values this is the same as a cast; for sequence values it gives a space-separated list. This method is refined for AtomicValues so that it never throws an Exception.

Specified by:

getStringValue in interface AtomicSequence

Specified by:

getStringValue in interface GroundedValue

Specified by:

getStringValue in interface Item

Returns:

the string value of the sequence.

See Also:

Item.getStringValueCS()

getPrimitiveStringValue

protected abstract CharSequence getPrimitiveStringValue()

Convert the value to a string, using the serialization rules for the primitive type. This is the result of conversion to a string except that postprocessing defined by the saxon:preprocess facet is not (yet) applied.

Returns:

the value converted to a string according to the rules for the primitive type

effectiveBooleanValue

public boolean effectiveBooleanValue()
                              throws XPathException

Get the effective boolean value of the value

Specified by:

effectiveBooleanValue in interface GroundedValue

Returns:

true, unless the value is boolean false, numeric zero, or zero-length string

Throws:

XPathException - if effective boolean value is not defined for this type (the default behaviour)

getComponent

public AtomicValue getComponent(AccessorFn.Component component)
                         throws XPathException

Method to extract components of a value. Implemented by some subclasses, but defined at this level for convenience

Parameters:

component - identifies the required component, as a constant defined in class AccessorFn

Returns:

the value of the requested component of this value

Throws:

XPathException - if a dynamic error occurs

UnsupportedOperationException - if applied to a value of a type that has no components

checkPermittedContents

public void checkPermittedContents(SchemaType parentType,
                          StaticContext env,
                          boolean whole)
                            throws XPathException

Check statically that the results of the expression are capable of constructing the content of a given schema type.

Parameters:

parentType - The schema type

env - the static context

whole - true if this atomic value accounts for the entire content of the containing node

Throws:

XPathException - if the expression doesn't match the required content type

asAtomic

public AtomicValue asAtomic()

Calling this method on a ConversionResult returns the AtomicValue that results from the conversion if the conversion was successful, and throws a ValidationException explaining the conversion error otherwise.

Use this method if you are calling a conversion method that returns a ConversionResult, and if you want to throw an exception if the conversion fails.

Specified by:

asAtomic in interface ConversionResult

Returns:

the atomic value that results from the conversion if the conversion was successful

toString

public String toString()

Get string value. In general toString() for an atomic value displays the value as it would be written in XPath: that is, as a literal if available, or as a call on a constructor function otherwise.

Overrides:

toString in class Object

iterator

public Iterator<AtomicValue> iterator()

Returns a Java iterator over the atomic sequence.

Specified by:

iterator in interface Iterable<AtomicValue>

Returns:

an Iterator.