Package net.sf.saxon.value
Class Value
- java.lang.Object
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- net.sf.saxon.value.Value
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- All Implemented Interfaces:
java.io.Serializable
,SequenceIterable
,ValueRepresentation
- Direct Known Subclasses:
AtomicValue
,Closure
,EmptySequence
,IntegerRange
,SequenceExtent
,ShareableSequence
,SingletonNode
public abstract class Value extends java.lang.Object implements java.io.Serializable, SequenceIterable, ValueRepresentation
A value is the result of an expression but it is also an expression in its own right. Note that every value can be regarded as a sequence - in many cases, a sequence of length one.- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description static java.lang.Class[]
EMPTY_CLASS_ARRAY
static int
INDETERMINATE_ORDERING
Constant returned by compareTo() method to indicate an indeterminate ordering between two values-
Fields inherited from interface net.sf.saxon.om.ValueRepresentation
EMPTY_VALUE_ARRAY
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Constructor Summary
Constructors Constructor Description Value()
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description Item
asItem()
Return the value in the form of an Itemstatic Item
asItem(ValueRepresentation value)
Static method to make an Item from a Valuestatic SequenceIterator
asIterator(ValueRepresentation val)
Static method to get an Iterator over any ValueRepresentation (which may be either a Value or a NodeInfostatic Value
asValue(ValueRepresentation val)
Static method to make a Value from a given Item (which may be either an AtomicValue or a NodeInfovoid
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.static java.lang.Object
convertToJava(Item item)
Convert an XPath value to a Java object.boolean
effectiveBooleanValue()
Get the effective boolean value of the expression.boolean
equals(java.lang.Object obj)
Compare two (sequence) values for equality.static Value
fromItem(Item item)
Static method to get a Value from an Itemjava.lang.CharSequence
getCanonicalLexicalRepresentation()
Get the canonical lexical representation as defined in XML Schema.int
getCardinality()
Determine the cardinalityItemType
getItemType(TypeHierarchy th)
Determine the data type of the items in the expression, if possiblestatic SequenceIterator
getIterator(ValueRepresentation val)
Get a SequenceIterator over a ValueRepresentationint
getLength()
Get the length of the sequencejava.lang.Comparable
getSchemaComparable()
Get a Comparable value that implements the XML Schema ordering comparison semantics for this value.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.Item
itemAt(int n)
Get the n'th item in the sequence (starting from 0).abstract SequenceIterator
iterate()
Iterate over the items contained in this value.SequenceIterator
iterate(XPathContext context)
Return an iterator over the results of evaluating an expressionstatic QNameValue
makeQNameValue(java.lang.Object object, Configuration config)
Temporary method to make a QNameValue from a JAXP 1.3 QName, without creating a compile-time link to the JDK 1.5 QName classvoid
process(XPathContext context)
Process the value as an instruction, without returning any tail callsValue
reduce()
Reduce a value to its simplest form.static double
stringToNumber(java.lang.CharSequence s)
Static method to convert strings to doubles.java.lang.String
toString()
Convert to a string for diagnostic output
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Field Detail
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INDETERMINATE_ORDERING
public static final int INDETERMINATE_ORDERING
Constant returned by compareTo() method to indicate an indeterminate ordering between two values- See Also:
- Constant Field Values
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EMPTY_CLASS_ARRAY
public static final java.lang.Class[] EMPTY_CLASS_ARRAY
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Method Detail
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asValue
public static Value asValue(ValueRepresentation val)
Static method to make a Value from a given Item (which may be either an AtomicValue or a NodeInfo- Parameters:
val
- The supplied value, or null, indicating the empty sequence.- Returns:
- The supplied value, if it is a value, or a SingletonNode that wraps the item, if it is a node. If the supplied value was null, return an EmptySequence
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asItem
public static Item asItem(ValueRepresentation value) throws XPathException
Static method to make an Item from a Value- Parameters:
value
- the value to be converted- Returns:
- null if the value is an empty sequence; or the only item in the value if it is a singleton sequence
- Throws:
XPathException
- if the Value contains multiple items
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asItem
public Item asItem() throws XPathException
Return the value in the form of an Item- Returns:
- the value in the form of an Item
- Throws:
XPathException
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fromItem
public static Value fromItem(Item item)
Static method to get a Value from an Item- Parameters:
item
- the supplied item- Returns:
- the item expressed as a Value
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asIterator
public static SequenceIterator asIterator(ValueRepresentation val) throws XPathException
Static method to get an Iterator over any ValueRepresentation (which may be either a Value or a NodeInfo- Parameters:
val
- The supplied value, or null, indicating the empty sequence.- Returns:
- The supplied value, if it is a value, or a SingletonNode that wraps the item, if it is a node. If the supplied value was null, return an EmptySequence
- Throws:
XPathException
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stringToNumber
public static double stringToNumber(java.lang.CharSequence s) throws java.lang.NumberFormatException
Static method to convert strings to doubles.- Parameters:
s
- the String to be converted- Returns:
- a double representing the value of the String
- Throws:
java.lang.NumberFormatException
- if the value cannot be converted
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getIterator
public static SequenceIterator getIterator(ValueRepresentation val) throws XPathException
Get a SequenceIterator over a ValueRepresentation- Parameters:
val
- the value to iterate over- Returns:
- the iterator
- Throws:
XPathException
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iterate
public abstract SequenceIterator iterate() throws XPathException
Iterate over the items contained in this value.- Returns:
- an iterator over the sequence of items
- Throws:
XPathException
- if a dynamic error occurs. This is possible only in the case of values that are materialized lazily, that is, where the iterate() method leads to computation of an expression that delivers the values.
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iterate
public final SequenceIterator iterate(XPathContext context) throws XPathException
Return an iterator over the results of evaluating an expression- Specified by:
iterate
in interfaceSequenceIterable
- Parameters:
context
- the dynamic evaluation context (not used in this implementation)- Returns:
- an iterator over the items delivered by the expression
- Throws:
XPathException
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getStringValueCS
public java.lang.CharSequence getStringValueCS() throws XPathException
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 interfaceValueRepresentation
- Throws:
XPathException
- The method can fail if evaluation of the value has been deferred, and if a failure occurs during the deferred evaluation. No failure is possible in the case of an AtomicValue or a Node.
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getCanonicalLexicalRepresentation
public java.lang.CharSequence getCanonicalLexicalRepresentation()
Get the canonical lexical representation as defined in XML Schema. This is not always the same as the result of casting to a string according to the XPath rules.- Returns:
- the canonical lexical representation if defined in XML Schema; otherwise, the result of casting to string according to the XPath 2.0 rules
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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.- Returns:
- for the default implementation: AnyItemType (not known)
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getCardinality
public int getCardinality()
Determine the cardinality- Returns:
- the cardinality
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itemAt
public Item itemAt(int n) throws XPathException
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.
- Throws:
XPathException
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getLength
public int getLength() throws XPathException
Get the length of the sequence- Returns:
- the number of items in the sequence
- Throws:
XPathException
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process
public void process(XPathContext context) throws XPathException
Process the value as an instruction, without returning any tail calls- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
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getStringValue
public java.lang.String getStringValue() throws XPathException
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.- Specified by:
getStringValue
in interfaceValueRepresentation
- Throws:
XPathException
- The method can fail if evaluation of the value has been deferred, and if a failure occurs during the deferred evaluation. No failure is possible in the case of an AtomicValue.
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effectiveBooleanValue
public boolean effectiveBooleanValue() throws XPathException
Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.- Returns:
- the effective boolean value
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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getSchemaComparable
public java.lang.Comparable getSchemaComparable()
Get a Comparable value that implements the XML Schema ordering comparison semantics for this value. The default implementation is written to compare sequences of atomic values. This method is overridden for AtomicValue and its subclasses.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
INDETERMINATE_ORDERING
when there is no defined order relationship between two given values.- Returns:
- a Comparable that follows XML Schema comparison rules
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equals
public boolean equals(java.lang.Object obj)
Compare two (sequence) values for equality. This method implements the XPath eq operator, for cases where it is defined. For values containing nodes, nodes are compared for identity. In cases where eq is not defined, it throws ClassCastException. In cases where the result of eq is an empty sequence, this function returns false, except that two empty sequences compare equal. The method also returns a ClassCastException if any failure occurs evaluating either of the values.- Overrides:
equals
in classjava.lang.Object
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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.- Parameters:
parentType
- The schema typeenv
- the static contextwhole
- true if this value accounts for the entire content of the containing node- Throws:
XPathException
- if the expression doesn't match the required content type
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reduce
public Value reduce() throws XPathException
Reduce a value to its simplest form. If the value is a closure or some other form of deferred value such as a FunctionCallPackage, then it is reduced to a SequenceExtent. If it is a SequenceExtent containing a single item, then it is reduced to that item. One consequence that is exploited by class FilterExpression is that if the value is a singleton numeric value, then the result will be an instance of NumericValue- Returns:
- the value in simplified form
- Throws:
XPathException
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makeQNameValue
public static QNameValue makeQNameValue(java.lang.Object object, Configuration config)
Temporary method to make a QNameValue from a JAXP 1.3 QName, without creating a compile-time link to the JDK 1.5 QName class- Parameters:
object
- an instance of javax.xml.namespace.QNameconfig
- the Saxon configuration (used for dynamic loading)- Returns:
- a corresponding Saxon QNameValue, or null if any error occurs performing the conversion
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toString
public java.lang.String toString()
Convert to a string for diagnostic output- Overrides:
toString
in classjava.lang.Object
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convertToJava
public static java.lang.Object convertToJava(Item item) throws XPathException
Convert an XPath value to a Java object. An atomic value is returned as an instance of the best available Java class. If the item is a node, the node is "unwrapped", to return the underlying node in the original model (which might be, for example, a DOM or JDOM node).- Parameters:
item
- the item to be converted- Returns:
- the value after conversion
- Throws:
XPathException
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