net.sf.saxon.value

Class AtomicValue

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.

Author: Michael H. Kay

Method Summary
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(int requiredType, XPathContext context)
Convert the value to a given type.
AtomicValueconvert(AtomicType targetType, XPathContext context, boolean validate)
Convert the value to a given type.
abstract AtomicValueconvertPrimitive(BuiltInAtomicType requiredType, boolean validate, XPathContext context)
Convert a value to another primitive data type, with control over how validation is handled.
voiddisplay(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure
booleaneffectiveBooleanValue(XPathContext context)
Get the effective boolean value of the value
StringevaluateAsString(XPathContext context)
Evaluate as a string
ItemevaluateItem(XPathContext context)
Evaluate the value (this simply returns the value unchanged)
intgetCardinality()
Determine the static cardinality
AtomicValuegetComponent(int component)
Method to extract components of a value.
intgetImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
intgetLength()
Get the length of the sequence
AtomicValuegetPrimitiveValue()
Get the primitive value (the value in the value space).
abstract 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
booleanhasBuiltInType()
Test whether the type of this atomic value is a built-in type.
SequenceIteratoriterate(XPathContext context)
Iterate over the (single) item in the sequence
voidprocess(XPathContext context)
Process the instruction, without returning any tail calls
booleanschemaEquals(Value obj)
Compare two values for equality.
StringtoString()
Get string value.

Method Detail

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(int requiredType, 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: 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

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.

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.

display

public final void display(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure

Parameters: level the indentation level of the output out

effectiveBooleanValue

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

evaluateAsString

public final String evaluateAsString(XPathContext context)
Evaluate as a string

evaluateItem

public Item evaluateItem(XPathContext context)
Evaluate the value (this simply returns the value unchanged)

Parameters: context the evaluation context (not used in this implementation)

Returns: the value, unchanged

Throws: XPathException

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

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.

getLength

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

Returns: always 1 for an atomic 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

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.

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.

getTypedValue

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

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

hasBuiltInType

public boolean hasBuiltInType()
Test whether the type of this atomic value is a built-in type. Default implementation returns true.

iterate

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

Parameters: context the evaluation context (not used in this implementation)

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.

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.

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.