net.sf.saxon.value
Class AtomicValue

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

All Implemented Interfaces:

Expression, Item, java.io.Serializable, ValueRepresentation

Direct Known Subclasses:

Base64BinaryValue, BooleanValue, CalendarValue, DerivedAtomicValue, DurationValue, HexBinaryValue, NumericValue, ObjectValue, QNameValue, StringValue

public abstract class AtomicValue

extends Value

implements Item

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 xdt: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.

See Also:

Serialized Form

Field Summary

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

EMPTY_CLASS_ARRAY

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

EMPTY_VALUE_ARRAY

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

AtomicValue()

Method Summary

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.
AtomicValue	convert(AtomicType targetType, XPathContext context, boolean validate) Convert the value to a given type.
AtomicValue	convert(int requiredType, XPathContext context) Convert the value to a given type.
abstract AtomicValue	convertPrimitive(BuiltInAtomicType requiredType, boolean validate, XPathContext context) Convert a value to another primitive data type, with control over how validation is handled.
void	display(int level, NamePool pool, java.io.PrintStream out) Diagnostic print of expression structure
boolean	effectiveBooleanValue(XPathContext context) Get the effective boolean value of the value
java.lang.String	evaluateAsString(XPathContext context) Evaluate as a string
Item	evaluateItem(XPathContext context) Evaluate the value (this simply returns the value unchanged)
int	getCardinality() Determine the static cardinality
AtomicValue	getComponent(int component) Method to extract components of a value.
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
int	getLength() Get the length of the sequence
AtomicValue	getPrimitiveValue() Get the primitive value (the value in the value space).
abstract java.lang.String	getStringValue() Convert the value to a string, using the serialization rules.
java.lang.CharSequence	getStringValueCS() Get the value of the item as a CharSequence.
SequenceIterator	getTypedValue() Get the typed value of this item
boolean	hasBuiltInType() Test whether the type of this atomic value is a built-in type.
SequenceIterator	iterate(XPathContext context) Iterate over the (single) item in the sequence
void	process(XPathContext context) Process the instruction, without returning any tail calls
boolean	schemaEquals(Value obj) Compare two values for equality.
java.lang.String	toString() Get string value.

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

asItem, asIterator, asValue, collapseWhitespace, convert, convertJavaObjectToXPath, convertToJava, equals, getDependencies, getItemType, getIterator, getParentExpression, getSpecialProperties, hashCode, itemAt, iterateSubExpressions, makeQNameValue, normalizeWhitespace, optimize, promote, reduce, simplify, stringToNumber, trimWhitespace, typeCheck

Methods inherited from class java.lang.Object

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

Constructor Detail

AtomicValue

public AtomicValue()

Method Detail

hasBuiltInType

public boolean hasBuiltInType()

Test whether the type of this atomic value is a built-in type. Default implementation returns true.

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 prefered.

Specified by:

getImplementationMethod in interface Expression

process

public void process(XPathContext context)
             throws XPathException

Process the instruction, without returning any tail calls

Specified by:

process in interface Expression

Overrides:

process in class Value

Parameters:

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

Throws:

XPathException

getCardinality

public final int getCardinality()

Determine the static cardinality

Specified by:

getCardinality in interface Expression

Overrides:

getCardinality in class Value

Returns:

code identifying the cardinality

See Also:

Cardinality

convert

public final AtomicValue convert(int requiredType,
                                 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:

requiredType - type code of the required atomic type

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

convertPrimitive

public abstract AtomicValue convertPrimitive(BuiltInAtomicType requiredType,
                                             boolean validate,
                                             XPathContext context)

Convert a value to another primitive data type, with control over how validation is handled.

Parameters:

requiredType - type code of the required atomic type

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 a date or time: it provides the implicit timezone.

Returns:

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

convert

public AtomicValue convert(AtomicType targetType,
                           XPathContext context,
                           boolean validate)

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

context - provides access to conversion context

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

Returns:

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

getLength

public final int getLength()

Get the length of the sequence

Overrides:

getLength in class Value

Returns:

always 1 for an atomic value

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the value (this simply returns the value unchanged)

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class Value

Parameters:

context - the evaluation context (not used in this implementation)

Returns:

the value, unchanged

Throws:

XPathException

iterate

public final SequenceIterator iterate(XPathContext context)

Iterate over the (single) item in the sequence

Specified by:

iterate in interface Expression

Parameters:

context - the evaluation context (not used in this implementation)

Returns:

a SequenceIterator that iterates over the single item in this value

evaluateAsString

public final java.lang.String evaluateAsString(XPathContext context)

Evaluate as a string

Specified by:

evaluateAsString in interface Expression

Overrides:

evaluateAsString in class Value

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the value of the expression, evaluated in the current context. The expression must return a string or (); if the value of the expression is (), this method returns "".

getStringValue

public abstract java.lang.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

Overrides:

getStringValue in class Value

getStringValueCS

public java.lang.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

Returns:

the string value of the item

See Also:

Item.getStringValue()

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)

getPrimitiveValue

public AtomicValue getPrimitiveValue()

Get the primitive value (the value in the value space). This returns an AtomicValue of a class that would be used to represent the primitive value. In effect this means that for built-in types, it returns the value itself, but for user-defined type, it returns the primitive value minus the type annotation. Note that getItemType() when applied to the result of this function does not not necessarily return a primitive type: for example, this function may return a value of type xdt:dayTimeDuration, which is not a primitive type as defined by Type.isPrimitiveType(int)

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException

Get the effective boolean value of the value

Specified by:

effectiveBooleanValue in interface Expression

Overrides:

effectiveBooleanValue in class Value

Parameters:

context - the evaluation context (not used in this implementation)

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

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.

Specified by:

checkPermittedContents in interface Expression

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

toString

public java.lang.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

schemaEquals

public boolean schemaEquals(Value obj)

Compare two values for equality. This supports identity constraints in XML Schema, which allow list-valued elements and attributes to participate in key and uniqueness constraints. This method returns false if any error occurs during the comparison, or if any of the items in either sequence is a node rather than an atomic value. The default implementation of schemaEquals() is the same as equals(), but subclasses can override this.

Overrides:

schemaEquals in class Value

display

public final void display(int level,
                          NamePool pool,
                          java.io.PrintStream out)

Diagnostic print of expression structure

Specified by:

display in interface Expression

Overrides:

display in class Value

Parameters:

level - the indentation level of the output

out -