com.hp.hpl.jena.graph
Class Node

java.lang.Object
  com.hp.hpl.jena.graph.Node

Direct Known Subclasses:

Node_Concrete, Node_Fluid

public abstract class Node
extends java.lang.Object

A Node has five subtypes: Node_Blank, Node_Anon, Node_URI, Node_Variable, and Node_ANY. Nodes are only constructed by the node factory methods, and they will attempt to re-use existing nodes with the same label if they are recent enough.

Author:

Jeremy Carroll and Chris Dollin

Nested Class Summary

static class

Node.NotLiteral Exception thrown if a literal-access operation is attemted on a non-literal node.

Field Summary

static Node	ANY The canonical instance of Node_ANY.
static Node	NULL The canonical NULL.

Method Summary

static void	cache(boolean wantCache) provided only for testing purposes.
static Node	create(com.hp.hpl.jena.graph.Node.NodeMaker maker, java.lang.Object label) We object strongly to null labels: for example, they make .equals flaky.
static Node	createAnon() make a blank node with a fresh anon id
static Node	createAnon(AnonId id) make a blank node with the specified label
static Node	createLiteral(com.hp.hpl.jena.graph.impl.LiteralLabel lit) make a literal node with the specified literal value
static Node	createLiteral(java.lang.String value)
static Node	createLiteral(java.lang.String lit, java.lang.String lang, boolean isXml) make a literal with specified language and XMLishness.
static Node	createLiteral(java.lang.String lex, java.lang.String lang, RDFDatatype dtype) Build a typed literal node from its lexical form.
static Node	createUncachedLiteral(java.lang.Object value, java.lang.String lang, RDFDatatype dtype)
static Node	createURI(java.lang.String uri) make a URI node with the specified URIref string
static Node	createVariable(java.lang.String name) make a variable node with a given name
abstract boolean	equals(java.lang.Object o) Nodes only equal other Nodes that have equal labels.
AnonId	getBlankNodeId() get the blank node id if the node is blank, otherwise die horribly
java.lang.String	getBlankNodeLabel() Answer the label of this blank node or throw an UnsupportedOperationException if it's not blank.
java.lang.Object	getIndexingValue() Answer the object which is the index value for this Node.
com.hp.hpl.jena.graph.impl.LiteralLabel	getLiteral() Answer the literal value of a literal node, or throw an UnsupportedOperationException if it's not a literal node
RDFDatatype	getLiteralDatatype() Answer the RDF datatype object of this node's literal value, if it is a literal; otherwise die horribly.
java.lang.String	getLiteralDatatypeURI() Answer the data-type URI of this node's literal value, if it is a literal; otherwise die horribly.
boolean	getLiteralIsXML()
java.lang.String	getLiteralLanguage() Answer the language of this node's literal value, if it is a literal; otherwise die horribly.
java.lang.String	getLiteralLexicalForm() Answer the lexical form of this node's literal value, if it is a literal; otherwise die horribly.
java.lang.Object	getLiteralValue() Answer the value of this node's literal value, if it is a literal; otherwise die horribly.
java.lang.String	getLocalName() get the localname part of this node if it's a URI node, else die horribly
java.lang.String	getName() get a variable nodes name, otherwise die horribly
java.lang.String	getNameSpace() get the namespace part of this node if it's a URI node, else die horribly
static RDFDatatype	getType(java.lang.String s)
java.lang.String	getURI() get the URI of this node if it has one, else die horribly
int	hashCode()
boolean	hasURI(java.lang.String uri) answer true iff this node is a URI node with the given URI
boolean	isBlank() Answer true iff this node is a blank node [subclasses override]
abstract boolean	isConcrete() Answer true iff this node is concrete, ie not variable, ie URI, blank, or literal.
boolean	isLiteral() Answer true iff this node is a literal node [subclasses override]
boolean	isURI() Answer true iff this node is a URI node [subclasses override]
boolean	isVariable() Answer true iff this node is a variable node - subclasses override
boolean	matches(Node other) Answer true iff this node accepts the other one as a match.
boolean	sameValueAs(java.lang.Object o) Test that two nodes are semantically equivalent.
java.lang.String	toString() Answer a human-readable representation of this Node.
java.lang.String	toString(boolean quoting) Answer a human-readable representation of this Node where literals are quoted according to quoting but URIs are not compressed.
java.lang.String	toString(PrefixMapping pm) Answer a human-readable representation of the Node, quoting literals and compressing URIs.
java.lang.String	toString(PrefixMapping pm, boolean quoting) Answer a human readable representation of this Node, quoting literals if specified, and compressing URIs using the prefix mapping supplied.
abstract java.lang.Object	visitWith(NodeVisitor v) Visit a Node and dispatch on it to the appropriate method from the NodeVisitor v.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Field Detail

ANY

public static final Node ANY

The canonical instance of Node_ANY. No other instances are required.

NULL

public static final Node NULL

The canonical NULL. It appears here so that revised definitions [eg as a bnode] that require the cache-and-maker system will work; the NodeMaker constants should be non-null at this point.

Method Detail

getType

public static RDFDatatype getType(java.lang.String s)

createAnon

public static Node createAnon()

make a blank node with a fresh anon id

createAnon

public static Node createAnon(AnonId id)

make a blank node with the specified label

createLiteral

public static Node createLiteral(com.hp.hpl.jena.graph.impl.LiteralLabel lit)

make a literal node with the specified literal value

createURI

public static Node createURI(java.lang.String uri)

make a URI node with the specified URIref string

createVariable

public static Node createVariable(java.lang.String name)

make a variable node with a given name

createLiteral

public static Node createLiteral(java.lang.String value)

createLiteral

public static Node createLiteral(java.lang.String lit,
                                 java.lang.String lang,
                                 boolean isXml)

make a literal with specified language and XMLishness. _lit_ must *not* be null.

Parameters:

isXml - If true then lit is exclusive canonical XML of type rdf:XMLLiteral, and no checking will be invoked.

createLiteral

public static Node createLiteral(java.lang.String lex,
                                 java.lang.String lang,
                                 RDFDatatype dtype)
                          throws DatatypeFormatException

Build a typed literal node from its lexical form. The lexical form will be parsed now and the value stored. If the form is not legal this will throw an exception.

Parameters:

lex - the lexical form of the literal

lang - the optional language tag

dtype - the type of the literal, null for old style "plain" literals

Throws:

DatatypeFormatException - if lex is not a legal form of dtype

createUncachedLiteral

public static Node createUncachedLiteral(java.lang.Object value,
                                         java.lang.String lang,
                                         RDFDatatype dtype)
                                  throws DatatypeFormatException

Throws:

DatatypeFormatException

visitWith

public abstract java.lang.Object visitWith(NodeVisitor v)

Visit a Node and dispatch on it to the appropriate method from the NodeVisitor v.

Parameters:

v - the visitor to apply to the node

Returns:

the value returned by the applied method

isConcrete

public abstract boolean isConcrete()

Answer true iff this node is concrete, ie not variable, ie URI, blank, or literal.

isLiteral

public boolean isLiteral()

Answer true iff this node is a literal node [subclasses override]

isBlank

public boolean isBlank()

Answer true iff this node is a blank node [subclasses override]

isURI

public boolean isURI()

Answer true iff this node is a URI node [subclasses override]

isVariable

public boolean isVariable()

Answer true iff this node is a variable node - subclasses override

getBlankNodeId

public AnonId getBlankNodeId()

get the blank node id if the node is blank, otherwise die horribly

getBlankNodeLabel

public java.lang.String getBlankNodeLabel()

Answer the label of this blank node or throw an UnsupportedOperationException if it's not blank.

getLiteral

public com.hp.hpl.jena.graph.impl.LiteralLabel getLiteral()

Answer the literal value of a literal node, or throw an UnsupportedOperationException if it's not a literal node

getLiteralValue

public java.lang.Object getLiteralValue()

Answer the value of this node's literal value, if it is a literal; otherwise die horribly.

getLiteralLexicalForm

public java.lang.String getLiteralLexicalForm()

Answer the lexical form of this node's literal value, if it is a literal; otherwise die horribly.

getLiteralLanguage

public java.lang.String getLiteralLanguage()

Answer the language of this node's literal value, if it is a literal; otherwise die horribly.

getLiteralDatatypeURI

public java.lang.String getLiteralDatatypeURI()

Answer the data-type URI of this node's literal value, if it is a literal; otherwise die horribly.

getLiteralDatatype

public RDFDatatype getLiteralDatatype()

Answer the RDF datatype object of this node's literal value, if it is a literal; otherwise die horribly.

getLiteralIsXML

public boolean getLiteralIsXML()

getIndexingValue

public java.lang.Object getIndexingValue()

Answer the object which is the index value for this Node. The default is this Node itself; overridden in Node_Literal for literal indexing purposes. Only concrete nodes should use this method.

getURI

public java.lang.String getURI()

get the URI of this node if it has one, else die horribly

getNameSpace

public java.lang.String getNameSpace()

get the namespace part of this node if it's a URI node, else die horribly

getLocalName

public java.lang.String getLocalName()

get the localname part of this node if it's a URI node, else die horribly

getName

public java.lang.String getName()

get a variable nodes name, otherwise die horribly

hasURI

public boolean hasURI(java.lang.String uri)

answer true iff this node is a URI node with the given URI

cache

public static void cache(boolean wantCache)

provided only for testing purposes. _cache(false)_ switches off caching and clears the cache. _cache(true)_ switches caching [back] on. This allows structural equality to be tested.

create

public static Node create(com.hp.hpl.jena.graph.Node.NodeMaker maker,
                          java.lang.Object label)

We object strongly to null labels: for example, they make .equals flaky. We reuse nodes from the recent cache if we can. Otherwise, the maker knows how to construct a new node of the correct class, and we add that node to the cache. create is synchronised to avoid threading problems - a separate thread might zap the cache entry that get is currently looking at.

equals

public abstract boolean equals(java.lang.Object o)

Nodes only equal other Nodes that have equal labels.

Overrides:

equals in class java.lang.Object

sameValueAs

public boolean sameValueAs(java.lang.Object o)

Test that two nodes are semantically equivalent. In some cases this may be the same as equals, in others equals is stricter. For example, two xsd:int literals with the same value but different language tag are semantically equivalent but distinguished by the java equality function in order to support round-tripping.

Default implementation is to use equals, subclasses should override this.

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

matches

public boolean matches(Node other)

Answer true iff this node accepts the other one as a match. The default is an equality test; it is over-ridden in subclasses to provide the appropriate semantics for literals, ANY, and variables.

Parameters:

other - a node to test for matching

Returns:

true iff this node accepts the other as a match

toString

public java.lang.String toString()

Answer a human-readable representation of this Node. It will not compress URIs, nor quote literals (because at the moment too many places use toString() for something machine-oriented).

Overrides:

toString in class java.lang.Object

toString

public java.lang.String toString(boolean quoting)

Answer a human-readable representation of this Node where literals are quoted according to quoting but URIs are not compressed.

toString

public java.lang.String toString(PrefixMapping pm)

Answer a human-readable representation of the Node, quoting literals and compressing URIs.

toString

public java.lang.String toString(PrefixMapping pm,
                                 boolean quoting)

Answer a human readable representation of this Node, quoting literals if specified, and compressing URIs using the prefix mapping supplied.