net.sf.saxon.value

Class AtomicValue

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

Field Summary
protected AtomicTypetypeLabel
Method Summary
AtomicValueasAtomic()
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.
voidcheckPermittedContents(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.
AtomicValueconvert(AtomicType schemaType, XPathContext context)
Convert the value to a given type.
ConversionResultconvert(AtomicType targetType, boolean validate, XPathContext context)
Convert the value to a given type.
protected abstract ConversionResultconvertPrimitive(BuiltInAtomicType requiredType, boolean validate, XPathContext context)
Convert a value to either (a) another primitive type, or (b) another built-in type derived from the current primitive type, with control over how validation is handled.
abstract AtomicValuecopyAsSubType(AtomicType typeLabel)
Create a copy of this atomic value, with a different type label
booleaneffectiveBooleanValue()
Get the effective boolean value of the value
abstract booleanequals(Object o)
The equals() methods on atomic values is defined to follow the semantics of eq when applied to two atomic values.
intgetCardinality()
Determine the static cardinality
AtomicValuegetComponent(int component)
Method to extract components of a value.
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the items in the expression, if possible
intgetLength()
Get the length of the sequence
protected abstract CharSequencegetPrimitiveStringValue()
Convert the value to a string, using the serialization rules for the primitive type.
abstract BuiltInAtomicTypegetPrimitiveType()
Determine the primitive type of the value.
abstract ComparablegetSchemaComparable()
Get a Comparable value that implements the XML Schema ordering comparison semantics for this value.
StringgetStringValue()
Convert the value to a string, using the serialization rules.
CharSequencegetStringValueCS()
Get the value of the item as a CharSequence.
SequenceIteratorgetTypedValue()
Get the typed value of this item
AtomicTypegetTypeLabel()
Determine the data type of the value.
abstract ObjectgetXPathComparable(boolean ordered, StringCollator collator, XPathContext context)
Get an object value that implements the XPath equality and ordering comparison semantics for this value.
booleanisIdentical(Value v)
Determine whether two atomic values are identical, as determined by XML Schema rules.
booleanisNaN()
Test whether the value is the double/float value NaN
ItemitemAt(int n)
Get the n'th item in the sequence (starting from 0).
SequenceIteratoriterate()
Iterate over the (single) item in the sequence
voidprocess(XPathContext context)
Process the instruction, without returning any tail calls
voidsetTypeLabel(AtomicType type)
Set the type label on this atomic value.
GroundedValuesubsequence(int start, int length)
Get a subsequence of the value
StringtoString()
Get string value.

Field Detail

typeLabel

protected AtomicType typeLabel

Method Detail

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.

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

checkPermittedContents

public 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.

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: net.sf.saxon.trans.XPathException if the expression doesn't match the required content type

convert

public final AtomicValue convert(AtomicType schemaType, 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 only where the target type is a built-in type.

Parameters: schemaType the required atomic type. This must not be a namespace-sensitive type such as QName or NOTATION 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. This must not be a namespace-sensitive type such as QName or NOTATION. 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.

convertPrimitive

protected abstract ConversionResult convertPrimitive(BuiltInAtomicType requiredType, boolean validate, XPathContext context)
Convert a value to either (a) another primitive type, or (b) another built-in type derived from the current primitive type, with control over how validation is handled.

Parameters: requiredType the required atomic type. This must either be a primitive type, or a built-in type derived from the same primitive type as this atomic value. validate true if validation is required. If set to false, the caller guarantees that the value is valid for the target data type, and that further validation is therefore not required. Note that a validation failure may be reported even if validation was not requested. context The conversion context to be used. This is required at present only when converting to xs:Name or similar types: it determines the NameChecker to be used.

Returns: the result of the conversion, if successful. If unsuccessful, the value returned will be a ValidationFailure. The caller must check for this condition. No exception is thrown, instead the exception information will be encapsulated within the ValidationFailure.

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

effectiveBooleanValue

public boolean effectiveBooleanValue()
Get the effective boolean value of the value

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

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().

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

getCardinality

public final int getCardinality()
Determine the static cardinality

Returns: code identifying the cardinality

See Also: Cardinality

getComponent

public AtomicValue getComponent(int component)
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 HOURS

Returns: the value of the requested component of this value

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the items in the expression, if possible

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)

getLength

public final int getLength()
Get the length of the sequence

Returns: always 1 for an atomic value

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

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

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 AtomicValue when there is no defined order relationship between two given values. This value is also returned when two values of different types are compared.

Returns: a Comparable that follows XML Schema comparison rules

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.

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.

getTypedValue

public final SequenceIterator getTypedValue()
Get the typed value of this item

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

getTypeLabel

public AtomicType getTypeLabel()
Determine the data type of the value. This delivers the same answer as AtomicValue, 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)

getXPathComparable

public 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. 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

isIdentical

public boolean isIdentical(Value 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.

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

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)

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.

iterate

public final SequenceIterator iterate()
Iterate over the (single) item in the sequence

Returns: a SequenceIterator that iterates over the single item in this value

process

public void process(XPathContext context)
Process the instruction, without returning any tail calls

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

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

Parameters: type the type label to be set

subsequence

public GroundedValue subsequence(int start, int length)
Get a subsequence of the value

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.