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org.neo4j.graphdb
Interface Node

All Superinterfaces:
PropertyContainer

public interface Node
extends PropertyContainer

A node in the graph with properties and relationships to other entities. Along with relationships, nodes are the core building blocks of the Neo4j data representation model. Nodes are created by invoking the GraphDatabaseService.createNode() method.

Node has three major groups of operations: operations that deal with relationships, operations that deal with properties (see PropertyContainer) 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 occurring one-to-zero-or-one association.

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 Neo4j does NOT accept arbitrary objects as property values. setProperty() takes a java.lang.Object only to avoid an explosion of overloaded setProperty() methods. For further documentation see PropertyContainer.

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

A node's id is unique, but may not be unique over time since neo4j reuses deleted ids. See wiki.neo4j.org/content/Id_Reuse.


Method Summary
 Relationship createRelationshipTo(Node otherNode, RelationshipType type)
          Creates a relationship between this node and another node.
 void delete()
          Deletes this node if it has no relationships attached to it.
 long getId()
          Returns the unique id of this node.
 Iterable<Relationship> getRelationships()
          Returns all the relationships attached to this node.
 Iterable<Relationship> getRelationships(Direction dir)
          Returns all OUTGOING or INCOMING relationships from this node.
 Iterable<Relationship> getRelationships(Direction direction, RelationshipType... types)
          Returns all the relationships of any of the types in types that are attached to this node and have the given direction.
 Iterable<Relationship> getRelationships(RelationshipType... types)
          Returns all the relationships of any of the types in types that are attached to this node, regardless of direction.
 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 hasRelationship()
          Returns true if there are any relationships attached to this node, false otherwise.
 boolean hasRelationship(Direction dir)
          Returns true if there are any relationships in the given direction attached to this node, false otherwise.
 boolean hasRelationship(Direction direction, RelationshipType... types)
          Returns true if there are any relationships of any of the types in types attached to this node (for the given direction), false otherwise.
 boolean hasRelationship(RelationshipType... types)
          Returns true if there are any relationships of any of the types in types attached to this node (regardless of direction), false otherwise.
 boolean hasRelationship(RelationshipType type, Direction dir)
          Returns true if there are any relationships of the given relationship type and direction attached to this node, false otherwise.
 Traverser traverse(Traverser.Order traversalOrder, StopEvaluator stopEvaluator, ReturnableEvaluator returnableEvaluator, 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.
 
Methods inherited from interface org.neo4j.graphdb.PropertyContainer
getGraphDatabase, getProperty, getProperty, getPropertyKeys, getPropertyValues, hasProperty, removeProperty, setProperty
 

Method Detail

getId

long getId()
Returns the unique id of this node. Ids are garbage collected over time so they are only guaranteed to be unique during a specific time span: if the node is deleted, it's likely that a new node at some point will get the old id. Note: this makes node ids brittle as public APIs.

Returns:
the id of this node

delete

void delete()
Deletes this node if it has no relationships attached to it. If delete() is invoked on a node with relationships, an unchecked exception will be raised when the transaction is committing. Invoking any methods on this node after delete() has returned is invalid and will lead to unspecified behavior.


getRelationships

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

hasRelationship

boolean hasRelationship()
Returns true if there are any relationships attached to this node, false otherwise.

Returns:
true if there are any relationships attached to this node, false otherwise

getRelationships

Iterable<Relationship> getRelationships(RelationshipType... types)
Returns all the relationships of any of the types in types that are attached to this node, regardless of direction. If no relationships of the given types are attached to this node, an empty iterable will be returned.

Parameters:
types - the given relationship type(s)
Returns:
all relationships of the given type(s) that are attached to this node

getRelationships

Iterable<Relationship> getRelationships(Direction direction,
                                        RelationshipType... types)
Returns all the relationships of any of the types in types that are attached to this node and have the given direction. If no relationships of the given types are attached to this node, an empty iterable will be returned.

Parameters:
types - the given relationship type(s)
direction - the direction of the relationships to return.
Returns:
all relationships of the given type(s) that are attached to this node

hasRelationship

boolean hasRelationship(RelationshipType... types)
Returns true if there are any relationships of any of the types in types attached to this node (regardless of direction), false otherwise.

Parameters:
types - the given relationship type(s)
Returns:
true if there are any relationships of any of the types in types attached to this node, false otherwise

hasRelationship

boolean hasRelationship(Direction direction,
                        RelationshipType... types)
Returns true if there are any relationships of any of the types in types attached to this node (for the given direction), false otherwise.

Parameters:
types - the given relationship type(s)
direction - the direction to check relationships for
Returns:
true if there are any relationships of any of the types in types attached to this node, false otherwise

getRelationships

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

hasRelationship

boolean hasRelationship(Direction dir)
Returns true if there are any relationships in the given direction attached to this node, false otherwise. If BOTH is passed in as a direction, relationships of both directions are matched (effectively turning this into hasRelationships()).

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:
true if there are any relationships in the given direction attached to this node, false otherwise

getRelationships

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

hasRelationship

boolean hasRelationship(RelationshipType type,
                        Direction dir)
Returns true if there are any relationships of the given relationship type and direction attached to this node, false otherwise.

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:
true if there are any relationships of the given relationship type and direction attached to this node, false otherwise

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:
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.

A relationship is equally well traversed in both directions so there's no need to create another relationship in the opposite direction (in regards to traversal or performance).

Parameters:
otherNode - the end node of the new relationship
type - the type of the new relationship
Returns:
the newly created relationship

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. The created traverser will iterate over each node that can be reached from this node by the spanning tree formed by the given relationship types (with direction) exactly once. 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_GRAPH 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. The created traverser will iterate over each node that can be reached from this node by the spanning tree formed by the given relationship types (with direction) exactly once. 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_GRAPH 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,
                   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.

The created traverser will iterate over each node that can be reached from this node by the spanning tree formed by the given relationship types (with direction) exactly once. 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_GRAPH 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:
RuntimeException - if the variable-length relationship type / direction list is not as described above

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