org.neo4j.api.core
Interface Node

public interface Node

Represents a node in the network with properties and relationships to other entities. Along with relationships, nodes are the core building blocks of the Neo data representation model. Nodes are created by invoking the EmbeddedNeo.createNode() method.

Node has three major groups of operations: operations that deal with relationships, operations that deal with properties and operations that create traversers.

The relationship operations provide a number of overloaded accessors (such as getRelationships(...) with "filters" for type, direction, etc), as well as the factory method createRelationshipTo(...) that connects two nodes with a relationship. It also includes the convenience method getSingleRelationship(...) for accessing the commonly occuring one-to-zero-or-one association. Of particular interest might be that there are no hasRelationship(...) methods. The idiomatic way to check if a node has any relationships matching a "filter" of type and direction is: if ( node.getRelationships(filter).iterator().hasNext() ) { ... }

The property operations give access to the key-value property pairs. Property keys are always strings. Valid property value types are all the Java primitives (int, byte, float, etc), java.lang.Strings and arrays of primitives and Strings. Please note that Neo does NOT accept arbitrary objects as property values. setProperty() takes a java.lang.Object for design reasons only.

The traversal factory methods instantiate a traverser that starts traversing from this node.

Method Summary

Relationship	createRelationshipTo(Node otherNode, RelationshipType type) Creates a relationship between this node and another node.
void	delete() Deletes this node.
long	getId() Returns the unique id of this node.
java.lang.Object	getProperty(java.lang.String key) Returns the property value associated with the given key.
java.lang.Object	getProperty(java.lang.String key, java.lang.Object defaultValue) Returns the property value associated with the given key, or a default value.
java.lang.Iterable<java.lang.String>	getPropertyKeys() Returns all currently valid property keys, or an empty iterable if this node has no properties.
java.lang.Iterable<java.lang.Object>	getPropertyValues() Returns all currently valid property values, or an empty iterable if this node has no properties.
java.lang.Iterable<Relationship>	getRelationships() Returns all the relationships attached to this node.
java.lang.Iterable<Relationship>	getRelationships(Direction dir) Returns all OUTGOING or INCOMING relationships from this node.
java.lang.Iterable<Relationship>	getRelationships(RelationshipType... type) Returns all the relationships of type type that are attached to this node, regardless of direction.
java.lang.Iterable<Relationship>	getRelationships(RelationshipType type, Direction dir) Returns all relationships with the given type and direction that are attached to this node.
Relationship	getSingleRelationship(RelationshipType type, Direction dir) Returns the only relationship of a given type and direction that is attached to this node, or null.
boolean	hasProperty(java.lang.String key) Returns true if this node has a property accessible through the given key, false otherwise.
java.lang.Object	removeProperty(java.lang.String key) Removes and returns the property associated with the given key.
void	setProperty(java.lang.String key, java.lang.Object value) Sets the property value for the given key to value.
Traverser	traverse(Traverser.Order traversalOrder, StopEvaluator stopEvaluator, ReturnableEvaluator returnableEvaluator, java.lang.Object... relationshipTypesAndDirections) Instantiates a traverser that will start at this node and traverse according to the given order and evaluators along the specified relationship type and direction pairs.
Traverser	traverse(Traverser.Order traversalOrder, StopEvaluator stopEvaluator, ReturnableEvaluator returnableEvaluator, RelationshipType relationshipType, Direction direction) Instantiates a traverser that will start at this node and traverse according to the given order and evaluators along the specified relationship type and direction.
Traverser	traverse(Traverser.Order traversalOrder, StopEvaluator stopEvaluator, ReturnableEvaluator returnableEvaluator, RelationshipType firstRelationshipType, Direction firstDirection, RelationshipType secondRelationshipType, Direction secondDirection) Instantiates a traverser that will start at this node and traverse according to the given order and evaluators along the two specified relationship type and direction pairs.

Method Detail

getId

long getId()

Returns the unique id of this node. Ids are garbage collected over time so are only guaranteed to be unique at a specific set of time: if the node is deleted, it's likely that a new node at some point will get the old id. This make node ids brittle as public APIs.

Returns:

the id of this node

delete

void delete()

Deletes this node. Invoking any methods on this node after delete() has returned is invalid and will lead to unspecified behavior.

getRelationships

java.lang.Iterable<Relationship> getRelationships()

Returns all the relationships attached to this node. If no relationships are attached to this node, an empty iterable will be returned.

Returns:

all relationships attached to this node

getRelationships

java.lang.Iterable<Relationship> getRelationships(RelationshipType... type)

Returns all the relationships of type type that are attached to this node, regardless of direction. If no relationships of the given type are attached to this node, an empty iterable will be returned.

Parameters:

type - the given relationship type(s)

Returns:

all relationships of the given type(s) that are attached to this node

getRelationships

java.lang.Iterable<Relationship> getRelationships(Direction dir)

Returns all OUTGOING or INCOMING relationships from this node. If there are no relationships with the given direction attached to this node, an empty iterable will be returned. If BOTH is passed in as a direction, relationships of both directions are returned (effectively turning this into getRelationships()).

Parameters:

dir - the given direction, where Direction.OUTGOING means all relationships that have this node as start node and Direction.INCOMING means all relationships that have this node as end node

Returns:

all relationships with the given direction that are attached to this node

getRelationships

java.lang.Iterable<Relationship> getRelationships(RelationshipType type,
                                                  Direction dir)

Returns all relationships with the given type and direction that are attached to this node. If there are no matching relationships, an empty iterable will be returned.

Parameters:

type - the given type

dir - the given direction, where Direction.OUTGOING means all relationships that have this node as start node and Direction.INCOMING means all relationships that have this node as end node

Returns:

all relationships attached to this node that match the given type and direction

getSingleRelationship

Relationship getSingleRelationship(RelationshipType type,
                                   Direction dir)

Returns the only relationship of a given type and direction that is attached to this node, or null. This is a convenience method that is used in the commonly occuring situation where a node has exactly zero or one relationships of a given type and direction to another node. Typically this invariant is maintained by the rest of the code: if at any time more than one such relationships exist, it is a fatal error that should generate an unchecked exception. This method reflects that semantics and returns either:

1. null if there are zero relationships of the given type and direction,
2. the relationship if there's exactly one, or
3. throws an unchecked exception in all other cases.

This method should be used only in situations with an invariant as described above. In those situations, a "state-checking" method (e.g. hasSingleRelationship(...)) is not required, because this method behaves correctly "out of the box."

Parameters:

type - the type of the wanted relationship

dir - the direction of the wanted relationship (where Direction.OUTGOING means a relationship that has this node as start node and Direction.INCOMING means a relationship that has this node as end node) or Direction.BOTH if direction is irrelevant

Returns:

the single relationship matching the given type and direction if exactly one such relationship exists, or null if exactly zero such relationships exists

Throws:

java.lang.RuntimeException - if more than one relationship matches the given type and direction

createRelationshipTo

Relationship createRelationshipTo(Node otherNode,
                                  RelationshipType type)

Creates a relationship between this node and another node. The relationship is of type type. It starts at this node and ends at otherNode.

Parameters:

otherNode - the end node of the new relationship

type - the type of the new relationship

Returns:

the newly created relationship

hasProperty

boolean hasProperty(java.lang.String key)

Returns true if this node has a property accessible through the given key, false otherwise. If key is null, this method returns false.

Parameters:

key - the property key

Returns:

true if this node has a property accessible through the given key, false otherwise

getProperty

java.lang.Object getProperty(java.lang.String key)

Returns the property value associated with the given key. The value is of one of the valid property types, i.e. a Java primitive, a String or an array of any of the valid types. If there's no property associated with key an unchecked exception is raised.

Parameters:

key - the property key

Returns:

the property value associated with the given key

Throws:

java.lang.RuntimeException - if there's no property associated with key

getProperty

java.lang.Object getProperty(java.lang.String key,
                             java.lang.Object defaultValue)

Returns the property value associated with the given key, or a default value. The value is of one of the valid property types, i.e. a Java primitive, a String or an array of any of the valid types. If defaultValue is not of a supported type, an unchecked exception is raised.

Parameters:

key - the property key

Returns:

the property value associated with the given key

Throws:

java.lang.IllegalArgumentException - if defaultValue is of an unsupported type

setProperty

void setProperty(java.lang.String key,
                 java.lang.Object value)

Sets the property value for the given key to value. The property value must be one of the valid property types, i.e:

• boolean or boolean[]
• byte or byte[]
• short or short[]
• int or int[]
• long or long[]
• float or float[]
• double or double[]
• char or char[]
• java.lang.String or String[]

Parameters:

key - the key with which the new property value will be associated

value - the new property value, of one of the valid property types

Throws:

java.lang.IllegalArgumentException - if value is of an unsuppoprted type

removeProperty

java.lang.Object removeProperty(java.lang.String key)

Removes and returns the property associated with the given key. If there's no property associated with the key, then null is returned.

Parameters:

key - the property key

Returns:

the property value that used to be associated with the given key

getPropertyKeys

java.lang.Iterable<java.lang.String> getPropertyKeys()

Returns all currently valid property keys, or an empty iterable if this node has no properties.

Returns:

all property keys

getPropertyValues

java.lang.Iterable<java.lang.Object> getPropertyValues()

Returns all currently valid property values, or an empty iterable if this node has no properties. All values are of a supported property type, i.e. a Java primitive, a String or an array of any of the supported types.

Returns:

all property values

traverse

Traverser traverse(Traverser.Order traversalOrder,
                   StopEvaluator stopEvaluator,
                   ReturnableEvaluator returnableEvaluator,
                   RelationshipType relationshipType,
                   Direction direction)

Instantiates a traverser that will start at this node and traverse according to the given order and evaluators along the specified relationship type and direction. If the traverser should traverse more than one RelationshipType/Direction pair, use one of the overloaded variants of this method. For more information about traversal, see the Traverser documentation.

Parameters:

traversalOrder - the traversal order

stopEvaluator - an evaluator instructing the new traverser about when to stop traversing, either a predefined evaluator such as StopEvaluator.END_OF_NETWORK or a custom-written evaluator

returnableEvaluator - an evaluator instructing the new traverser about whether a specific node should be returned from the traversal, either a predefined evaluator such as ReturnableEvaluator.ALL or a customer-written evaluator

relationshipType - the relationship type that the traverser will traverse along

direction - the direction in which the relationships of type relationshipType will be traversed

Returns:

a new traverser, configured as above

traverse

Traverser traverse(Traverser.Order traversalOrder,
                   StopEvaluator stopEvaluator,
                   ReturnableEvaluator returnableEvaluator,
                   RelationshipType firstRelationshipType,
                   Direction firstDirection,
                   RelationshipType secondRelationshipType,
                   Direction secondDirection)

Instantiates a traverser that will start at this node and traverse according to the given order and evaluators along the two specified relationship type and direction pairs. If the traverser should traverse more than two RelationshipType/Direction pairs, use the overloaded varargs variant of this method. For more information about traversal, see the Traverser documentation.

Parameters:

traversalOrder - the traversal order

stopEvaluator - an evaluator instructing the new traverser about when to stop traversing, either a predefined evaluator such as StopEvaluator.END_OF_NETWORK or a custom-written evaluator

returnableEvaluator - an evaluator instructing the new traverser about whether a specific node should be returned from the traversal, either a predefined evaluator such as ReturnableEvaluator.ALL or a customer-written evaluator

firstRelationshipType - the first of the two relationship types that the traverser will traverse along

firstDirection - the direction in which the first relationship type will be traversed

secondRelationshipType - the second of the two relationship types that the traverser will traverse along

secondDirection - the direction that the second relationship type will be traversed

Returns:

a new traverser, configured as above

traverse

Traverser traverse(Traverser.Order traversalOrder,
                   StopEvaluator stopEvaluator,
                   ReturnableEvaluator returnableEvaluator,
                   java.lang.Object... relationshipTypesAndDirections)

Instantiates a traverser that will start at this node and traverse according to the given order and evaluators along the specified relationship type and direction pairs. Unlike the overloaded variants of this method, the relationship types and directions are passed in as a "varargs" variable-length argument which means that an arbitrary set of relationship type and direction pairs can be specified. The variable-length argument list should be every other relationship type and direction, starting with relationship type, e.g:

node.traverse( BREADTH_FIRST, stopEval, returnableEval, MyRels.REL1, Direction.OUTGOING, MyRels.REL2, Direction.OUTGOING, MyRels.REL3, Direction.BOTH, MyRels.REL4, Direction.INCOMING );

Unfortunately, the compiler cannot enforce this so an unchecked exception is raised if the variable-length argument has a different constitution.

For more information about traversal, see the Traverser documentation.

Parameters:

traversalOrder - the traversal order

stopEvaluator - an evaluator instructing the new traverser about when to stop traversing, either a predefined evaluator such as StopEvaluator.END_OF_NETWORK or a custom-written evaluator

returnableEvaluator - an evaluator instructing the new traverser about whether a specific node should be returned from the traversal, either a predefined evaluator such as ReturnableEvaluator.ALL or a customer-written evaluator

relationshipTypesAndDirections - a variable-length list of relationship types and their directions, where the first argument is a relationship type, the second argument the first type's direction, the third a relationship type, the fourth its direction, etc

Returns:

a new traverser, configured as above

Throws:

java.lang.RuntimeException - if the variable-length relationship type / direction list is not as described above