org.neo4j.api.core
Interface Relationship

public interface Relationship

Represents a relationship between two nodes in the network. A relationship has a start node, an end node and a type. You can attach properties to relationships with the exact same API as with nodes.

Relationships are created by invoking the Node.createRelationshipTo() method on a node as follows:

Relationship rel = node.createRelationshipTo( otherNode, MyRels.REL_TYPE );

The fact that the relationship API gives meaning to start and end nodes implicitly means that all relationships have a direction. In the example above, rel would be directed from node to otherNode. A relationship's start node and end node and their relation to Direction.OUTGOING and Direction.INCOMING are defined so that the assertions in the following code are true:

 Node a = neo.createNode(), b = neo.createNode();
 Relationship rel = a.createRelationshipTo( b, MyRels.REL_TYPE );
 // Now we have: (a) --- REL_TYPE ---> (b)
 
 assert rel.getStartNode().equals( a );
 assert rel.getEndNode().equals( b );
 assert rel.getNodes()[0].equals( a ) && rel.getNodes()[1].equals( b );
 
 rel = b.getSingleRelationship( MyRels.REL_TYPE, Direction.INCOMING ) ;
 assert rel.getStartNode().equals( b );
 assert rel.getEndNode().equals( a );
 assert rel.getNodes()[0].equals( b ) && rel.getNodes()[1].equals( a );
 

Furthermore, Neo guarantees that a relationship is never "hanging freely," i.e. getStartNode(), getEndNode(), getOtherNode(Node) and getNodes() are guaranteed to always return valid, non-null nodes.

Method Summary

void	delete() Deletes this relationship.
Node	getEndNode() Returns the end node of this relationship.
long	getId()
Node[]	getNodes() Returns the two nodes that are attached to this relationship.
Node	getOtherNode(Node node) A convenience operation that, given a node that is attached to this relationship, returns the other node.
Object	getProperty(String key) See Node.getProperty(String)
Object	getProperty(String key, Object defaultValue) See Node.getProperty(String, Object)
Iterable<String>	getPropertyKeys() See Node.getPropertyKeys()
Iterable<Object>	getPropertyValues() See Node.getPropertyValues()
Node	getStartNode() Returns the start node of this relationship.
RelationshipType	getType() Returns the type of this relationship.
boolean	hasProperty(String key) See Node.hasProperty(String)
Object	removeProperty(String key) See Node.removeProperty(String)
void	setProperty(String key, Object value) See Node.setProperty(String, Object)

Method Detail

getId

long getId()

delete

void delete()

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

getStartNode

Node getStartNode()

Returns the start node of this relationship. For a definition of how start node relates to directions as arguments to the relationship accessors in Node, see the class documentation of Relationship.

Returns:

the start node of this relationship

getEndNode

Node getEndNode()

Returns the end node of this relationship. For a definition of how end node relates to directions as arguments to the relationship accessors in Node, see the class documentation of Relationship.

Returns:

the end node of this relationship

getOtherNode

Node getOtherNode(Node node)

A convenience operation that, given a node that is attached to this relationship, returns the other node. For example if node is a start node, the end node will be returned, and vice versa. This is a very convenient operation when you're manually traversing the node space by invoking one of the getRelationships() operations on node. For example, to get the node "at the other end" of a relationship, use the following:

Node endNode = node.getSingleRelationship( MyRels.REL_TYPE ).getOtherNode ( node );

This operation will throw a runtime exception if node is neither this relationship's start node nor its end node.

Parameters:

node - the start or end node of this relationship

Returns:

the other node

Throws:

RuntimeException - if the given node is neither the start nor end node of this relationship

getNodes

Node[] getNodes()

Returns the two nodes that are attached to this relationship. First element in the array will be the start node, the second element the end node.

Returns:

the two nodes that are attached to this relationship

getType

RelationshipType getType()

Returns the type of this relationship. A relationship's type is an immutable property that is specified at Relationship creation. It will always be one of the elements of the RelationshipType enumeration passed in to EmbeddedNeo at startup.

Returns:

the type of this relationship

hasProperty

boolean hasProperty(String key)

See Node.hasProperty(String)

getProperty

Object getProperty(String key)

See Node.getProperty(String)

getProperty

Object getProperty(String key,
                   Object defaultValue)

See Node.getProperty(String, Object)

setProperty

void setProperty(String key,
                 Object value)

See Node.setProperty(String, Object)

removeProperty

Object removeProperty(String key)

See Node.removeProperty(String)

getPropertyKeys

Iterable<String> getPropertyKeys()

See Node.getPropertyKeys()

getPropertyValues

Iterable<Object> getPropertyValues()

See Node.getPropertyValues()