net.sf.saxon.value
Class AtomicValue

java.lang.Object
  net.sf.saxon.value.Value
      net.sf.saxon.value.AtomicValue

All Implemented Interfaces:

Serializable, PullEvent, SequenceIterable, GroundedValue, Item, ValueRepresentation, ConversionResult

Direct Known Subclasses:

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

public abstract class AtomicValue
extends Value
implements Item, GroundedValue, ConversionResult

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

See Also:

Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.value.Value

EMPTY_CLASS_ARRAY, INDETERMINATE_ORDERING

Fields inherited from interface net.sf.saxon.om.ValueRepresentation

EMPTY_VALUE_ARRAY

Fields inherited from interface net.sf.saxon.om.ValueRepresentation

EMPTY_VALUE_ARRAY

Constructor Summary

AtomicValue()

Method Summary

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.
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.
ConversionResult	convert(AtomicType targetType, boolean validate, XPathContext context) Convert the value to a given type.
AtomicValue	convert(AtomicType schemaType, XPathContext context) Convert the value to a given 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.
int	getCardinality() Determine the static cardinality
AtomicValue	getComponent(int component) Method to extract components of a value.
ItemType	getItemType(TypeHierarchy th) Determine the data type of the items in the expression, if possible
int	getLength() Get the length of the sequence
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.
abstract String	getStringValue() Convert the value to a string, using the serialization rules.
CharSequence	getStringValueCS() Get the value of the item as a CharSequence.
SequenceIterator	getTypedValue() Get the typed value of this item
AtomicType	getTypeLabel() Determine the data type of the value.
abstract Object	getXPathComparable(boolean ordered, StringCollator collator, XPathContext context) Get an object value that implements the XPath equality and ordering comparison semantics for this value.
boolean	isNaN() Test whether the value is the double/float value NaN
Item	itemAt(int n) Get the n'th item in the sequence (starting from 0).
SequenceIterator	iterate() Iterate over the (single) item in the 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.
GroundedValue	subsequence(int start, int length) Get a subsequence of the value
String	toString() Get string value.

Methods inherited from class net.sf.saxon.value.Value

asItem, asItem, asIterator, asValue, convertJavaObjectToXPath, convertToJava, convertToJava, fromItem, getCanonicalLexicalRepresentation, getIterator, iterate, makeQNameValue, reduce, stringToNumber

Methods inherited from class java.lang.Object

getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

AtomicValue

public AtomicValue()

Method Detail

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 Value.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.

Overrides:

getSchemaComparable in class Value

Returns:

a Comparable that follows XML Schema comparison rules

getXPathComparable

public abstract Object getXPathComparable(boolean ordered,
                                          StringCollator collator,
                                          XPathContext context)
                                   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 context argument is supplied for use in cases where the comparison semantics are context-sensitive, for example where they depend on the implicit timezone or the default collation.

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

context - the XPath dynamic evaluation context, used in cases where the comparison is context sensitive

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 comparison depends on dynamic context information that is not available, for example implicit timezone

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 Value

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

getStringValueCS

public 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 Item

Specified by:

getStringValueCS in interface ValueRepresentation

Overrides:

getStringValueCS in class Value

Returns:

the string value of the item

See Also:

Item.getStringValue()

process

public void process(XPathContext context)
             throws XPathException

Process the instruction, without returning any tail calls

Overrides:

process in class Value

Parameters:

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

Throws:

XPathException

itemAt

public final Item 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 GroundedValue

Overrides:

itemAt in class Value

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 ItemType getItemType(TypeHierarchy th)

Determine the data type of the items in the expression, if possible

Overrides:

getItemType in class Value

Parameters:

th - The TypeHierarchy. Can be null if the target is an AtomicValue, except in the case where it is an external ObjectValue.

Returns:

for the default implementation: AnyItemType (not known)

getTypeLabel

public AtomicType getTypeLabel()

Determine the data type of the value. This delivers the same answer as getItemType(net.sf.saxon.type.TypeHierarchy), except in the case of external objects (instances of ObjectValue, where the method may deliver a less specific type.

Returns:

for the default implementation: AnyItemType (not known)

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

getCardinality

public final int getCardinality()

Determine the static cardinality

Overrides:

getCardinality in class Value

Returns:

code identifying the cardinality

See Also:

Cardinality

convert

public final AtomicValue convert(AtomicType schemaType,
                                 XPathContext context)
                          throws XPathException

Convert the value to a given type. The result of the conversion will be an atomic value of the required type. This method works only where the target type is a built-in type.

Parameters:

schemaType - the required atomic type

context - the XPath dynamic context

Returns:

the result of the conversion, if conversion was possible. This will always be an instance of the class corresponding to the type of value requested

Throws:

XPathException - if conversion is not allowed for this required type, or if the particular value cannot be converted

convert

public final ConversionResult convert(AtomicType targetType,
                                      boolean validate,
                                      XPathContext context)

Convert the value to a given type. The result of the conversion will be an atomic value of the required type. This method works where the target type is a built-in atomic type and also where it is a user-defined atomic type.

Parameters:

targetType - the type to which the value is to be converted

validate - true if validation is required, false if the caller already knows that the value is valid

context - provides access to conversion context

Returns:

the value after conversion if successful; or a ValidationFailure if conversion failed. The caller must check for this condition. Validation may fail even if validation was not requested.

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 double/float value NaN

Returns:

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

getLength

public final int getLength()

Get the length of the sequence

Overrides:

getLength in class Value

Returns:

always 1 for an atomic value

iterate

public final SequenceIterator iterate()

Iterate over the (single) item in the sequence

Specified by:

iterate in class Value

Returns:

a SequenceIterator that iterates over the single item in this value

getStringValue

public abstract 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 Item

Specified by:

getStringValue in interface ValueRepresentation

Overrides:

getStringValue in class Value

Returns:

the string value of the item

See Also:

Item.getStringValueCS()

getTypedValue

public final SequenceIterator getTypedValue()

Get the typed value of this item

Specified by:

getTypedValue in interface Item

Returns:

the typed value of the expression (which is this value)

effectiveBooleanValue

public boolean effectiveBooleanValue()
                              throws XPathException

Get the effective boolean value of the value

Overrides:

effectiveBooleanValue in class Value

Returns:

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

Throws:

XPathException - if any dynamic error occurs evaluating the expression

getComponent

public AtomicValue getComponent(int 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 Component, for example Component.HOURS

Returns:

the value of the requested component of this value

Throws:

XPathException

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.

Overrides:

checkPermittedContents in class Value

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

subsequence

public GroundedValue subsequence(int start,
                                 int length)

Get a subsequence of the value

Specified by:

subsequence in interface GroundedValue

Parameters:

start - the index of the first item to be included in the result, counting from zero. A negative value is taken as zero. If the value is beyond the end of the sequence, an empty sequence is returned

length - the number of items to be included in the result. Specify Integer.MAX_VALUE to get the subsequence up to the end of the base sequence. If the value is negative, an empty sequence is returned. If the value goes off the end of the sequence, the result returns items up to the end of the sequence

Returns:

the required subsequence. If min is

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 Value