Package net.sf.saxon.type

Interface ItemType

All Known Subinterfaces:

AtomicType, FunctionItemType, ItemType.WithSequenceTypeCache, PlainType, TupleType, UnionType

All Known Implementing Classes:

AnyChildNodeTest, AnyExternalObjectType, AnyFunctionType, AnyFunctionTypeWithAssertions, AnyItemType, AnyNodeTest, ArrayItemType, BuiltInAtomicType, CombinedNodeTest, ContentTypeTest, DocumentNodeTest, ErrorType, ExternalObjectType, JavaExternalObjectType, LocalNameTest, MapType, MultipleNodeKindTest, NamespaceTest, NameTest, NodeKindTest, NodeTest, NumericType, SameNameTest, SpecificFunctionType, TupleItemType

public interface ItemType

ItemType is an interface that allows testing of whether an Item conforms to an expected type. ItemType represents the types in the type hierarchy in the XPath model, as distinct from the schema model: an item type is either item() (matches everything), a node type (matches nodes), an atomic type (matches atomic values), or empty() (matches nothing). Atomic types, represented by the class AtomicType, are also instances of SimpleType in the schema type hierarchy. Node Types, represented by the class NodeTest, are also Patterns as used in XSLT.

Saxon assumes that apart from AnyItemType (which corresponds to item() and matches anything), every ItemType will be either an AtomicType, a NodeTest, or a FunctionItemType. User-defined implementations of ItemType must therefore extend one of those three classes/interfaces.

See Also:

AtomicType, NodeTest, FunctionItemType

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	ItemType.WithSequenceTypeCache	Extension of the ItemType interface implemented by some item types, to provide a cache of SequenceType objects based on this item type, with different occurrence indicators.

Method Summary

Modifier and Type	Method	Description
default java.util.Optional<java.lang.String>	explainMismatch(Item item, TypeHierarchy th)	Get extra diagnostic information about why a supplied item does not conform to this item type, if available.
java.lang.String	generateJavaScriptItemTypeAcceptor(java.lang.String errorCode, int targetVersion)	Generate Javascript code to convert a supplied Javascript value to this item type, if conversion is possible, or throw an error otherwise.
java.lang.String	generateJavaScriptItemTypeTest(ItemType knownToBe, int targetVersion)	Generate Javascript code to test whether an item conforms to this item type
java.lang.String	getAlphaCode()	Get an alphabetic code representing the type, or at any rate, the nearest built-in type from which this type is derived.
PlainType	getAtomizedItemType()	Get the item type of the atomic values that will be produced when an item of this type is atomized
Genre	getGenre()	Determine the Genre (top-level classification) of this type
ItemType	getPrimitiveItemType()	Get the primitive item type corresponding to this item type.
int	getPrimitiveType()	Get the primitive type corresponding to this item type.
UType	getUType()	Get the corresponding UType.
boolean	isAtomicType()	Determine whether this item type is an atomic type
boolean	isAtomizable(TypeHierarchy th)	Ask whether values of this type are atomizable
boolean	isPlainType()	Determine whether this item type is a plain type (that is, whether it can ONLY match atomic values)
default boolean	isTrueItemType()	Ask whether this ItemType actually represents an item type in the XDM sense of the term.
boolean	matches(Item item, TypeHierarchy th)	Test whether a given item conforms to this type
default java.lang.String	toExportString()	Return a string representation of this ItemType suitable for use in stylesheet export files.
java.lang.String	toString()

Method Detail

getGenre

Genre getGenre()

Determine the Genre (top-level classification) of this type

Returns:

the Genre to which this type belongs, for example node or atomic value

isAtomicType

boolean isAtomicType()

Determine whether this item type is an atomic type

Returns:

true if this is ANY_ATOMIC_TYPE or a subtype thereof

isPlainType

boolean isPlainType()

Determine whether this item type is a plain type (that is, whether it can ONLY match atomic values)

Returns:

true if this is ANY_ATOMIC_TYPE or a subtype thereof, or a "plain" union type (that is, unions of atomic types that impose no further restrictions). Return false if this is a union type whose member types are not all known.

isTrueItemType

default boolean isTrueItemType()

Ask whether this ItemType actually represents an item type in the XDM sense of the term. The only instances that aren't true item types are user-defined union types derived by restriction from other union types or containing list types in their transitive membership ("impure union types")

Returns:

true if this is a true item type in the XDM sense

matches

boolean matches(Item item,
                TypeHierarchy th)
         throws XPathException

Test whether a given item conforms to this type

Parameters:

item - The item to be tested

th - The type hierarchy cache. Currently used only when matching function items.

Returns:

true if the item is an instance of this type; false otherwise

Throws:

XPathException

getPrimitiveItemType

ItemType getPrimitiveItemType()

Get the primitive item type corresponding to this item type. For item(), this is Type.ITEM. For node(), it is Type.NODE. For specific node kinds, it is the value representing the node kind, for example Type.ELEMENT. For anyAtomicValue and union types it is Type.ATOMIC_VALUE. For numeric it is Type.NUMBER. For other atomic types it is the primitive type as defined in XML Schema, except that integer, xs:dayTimeDuration, and xs:yearMonthDuration are considered to be primitive types.

Returns:

the corresponding primitive type

getPrimitiveType

int getPrimitiveType()

Get the primitive type corresponding to this item type. For item(), this is Type.ITEM. For node(), it is Type.NODE. For specific node kinds, it is the value representing the node kind, for example Type.ELEMENT. For anyAtomicValue it is BuiltInAtomicType.ANY_ATOMIC. For numeric it is Type.NUMBER. For other atomic types it is the primitive type as defined in XML Schema, except that INTEGER is considered to be a primitive type.

Returns:

the integer fingerprint of the corresponding primitive type

getUType

UType getUType()

Get the corresponding UType. A UType is a union of primitive item types.

Returns:

the smallest UType that subsumes this item type

getAtomizedItemType

PlainType getAtomizedItemType()

Get the item type of the atomic values that will be produced when an item of this type is atomized

Returns:

the best available item type of the atomic values that will be produced when an item of this type is atomized, or null if it is known that atomization will throw an error.

isAtomizable

boolean isAtomizable(TypeHierarchy th)

Ask whether values of this type are atomizable

Parameters:

th - the type hierarchy cache

Returns:

true if some or all instances of this type can be successfully atomized; false if no instances of this type can be atomized

getAlphaCode

java.lang.String getAlphaCode()

Get an alphabetic code representing the type, or at any rate, the nearest built-in type from which this type is derived. The codes are designed so that for any two built-in types A and B, alphaCode(A) is a prefix of alphaCode(B) if and only if A is a supertype of B.

Returns:

the alphacode for the nearest containing built-in type

toExportString

default java.lang.String toExportString()

Return a string representation of this ItemType suitable for use in stylesheet export files. This differs from the result of toString() in that it will not contain any references to anonymous types. Note that it may also use the Saxon extended syntax for union types and tuple types. The default implementation returns the result of calling toString().

Returns:

the string representation as an instance of the XPath SequenceType construct

generateJavaScriptItemTypeTest

java.lang.String generateJavaScriptItemTypeTest(ItemType knownToBe,
                                                int targetVersion)
                                         throws XPathException

Generate Javascript code to test whether an item conforms to this item type

Parameters:

knownToBe - An item type that the supplied item is known to conform to; the generated code can assume that the item is an instance of this type.

targetVersion - The version of Saxon-JS for which code is being generated. Currently either 1 or 2.

Returns:

a Javascript instruction or sequence of instructions, which can be used as the body of a Javascript function, and which returns a boolean indication whether the value of the variable "item" is an instance of this item type.

Throws:

XPathException - if JS code cannot be generated for this item type, for example because the test is schema-aware.

generateJavaScriptItemTypeAcceptor

java.lang.String generateJavaScriptItemTypeAcceptor(java.lang.String errorCode,
                                                    int targetVersion)
                                             throws XPathException

Generate Javascript code to convert a supplied Javascript value to this item type, if conversion is possible, or throw an error otherwise.

Parameters:

errorCode - the error to be thrown if conversion is not possible

targetVersion - the version of Saxon-JS for which code is being generated

Returns:

a Javascript instruction or sequence of instructions, which can be used as the body of a Javascript function, and which returns the result of conversion to this type, or throws an error if conversion is not possible. The variable "val" will hold the supplied Javascript value.

Throws:

XPathException

toString

java.lang.String toString()

Overrides:

toString in class java.lang.Object

explainMismatch

default java.util.Optional<java.lang.String> explainMismatch(Item item,
                                                             TypeHierarchy th)

Get extra diagnostic information about why a supplied item does not conform to this item type, if available. If extra information is returned, it should be in the form of a complete sentence, minus the closing full stop. No information should be returned for obvious cases.

Parameters:

item - the item that doesn't match this type

th - the type hierarchy cache

Returns:

optionally, a message explaining why the item does not match the type