Class AtomicValue

java.lang.Object
net.sf.saxon.value.Value<AtomicValue>
net.sf.saxon.value.AtomicValue
All Implemented Interfaces:
PullEvent, GroundedValue<AtomicValue>, Item<AtomicValue>, ValueRepresentation<AtomicValue>, ConversionResult
Direct Known Subclasses:
Base64BinaryValue, BooleanValue, CalendarValue, DurationValue, HexBinaryValue, NumericValue, ObjectValue, QualifiedNameValue, StringValue

public abstract class AtomicValue extends Value<AtomicValue> implements Item<AtomicValue>, GroundedValue<AtomicValue>, 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 Details

  • Constructor Details

    • AtomicValue

      public AtomicValue()
  • Method Details

    • 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<AtomicValue>
      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<AtomicValue>
      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(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.

      Overrides:
      isIdentical in class Value<AtomicValue>
      Parameters:
      v - the other value to be compared with this one
      Returns:
      true if the two values are identical, false otherwise.
    • 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 Item<AtomicValue>
      Specified by:
      getStringValueCS in interface ValueRepresentation<AtomicValue>
      Overrides:
      getStringValueCS in class Value<AtomicValue>
      Returns:
      the result of converting the value to a string
      See Also:
    • process

      public void process(XPathContext context) throws XPathException
      Process the instruction, without returning any tail calls
      Overrides:
      process in class Value<AtomicValue>
      Parameters:
      context - The dynamic context, giving access to the current node, the current variables, etc.
      Throws:
      XPathException - if an error occurs (for example if the value is a closure that needs to be evaluated)
    • 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 GroundedValue<AtomicValue>
      Overrides:
      itemAt in class Value<AtomicValue>
      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<AtomicValue>
      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<AtomicValue>
      Returns:
      code identifying the cardinality
      See Also:
    • 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
    • getLength

      public final int getLength()
      Get the length of the sequence
      Specified by:
      getLength in interface GroundedValue<AtomicValue>
      Overrides:
      getLength in class Value<AtomicValue>
      Returns:
      always 1 for an atomic value
    • iterate

      public final SequenceIterator<AtomicValue> iterate()
      Iterate over the (single) item in the sequence
      Specified by:
      iterate in class Value<AtomicValue>
      Returns:
      a SequenceIterator that iterates over the single item in this value
    • 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 Item<AtomicValue>
      Specified by:
      getStringValue in interface ValueRepresentation<AtomicValue>
      Overrides:
      getStringValue in class Value<AtomicValue>
      Returns:
      the result of converting the value to a string
      See Also:
    • 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
    • getTypedValue

      public final SequenceIterator<AtomicValue> getTypedValue()
      Get the typed value of this item
      Specified by:
      getTypedValue in interface Item<AtomicValue>
      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<AtomicValue>
      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 - 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.
      Overrides:
      checkPermittedContents in class Value<AtomicValue>
      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<AtomicValue> subsequence(int start, int length)
      Get a subsequence of the value
      Specified by:
      subsequence in interface GroundedValue<AtomicValue>
      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 Object