org.neo4j.graphdb

Interface Node

  • All Superinterfaces:
    Entity, PropertyContainer


    public interface Node
    extends Entity
    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 deal with labels.

    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.

    A node's id is unique, but note the following: Neo4j reuses its internal ids when nodes and relationships are deleted, which means it's bad practice to refer to them this way. Instead, use application generated ids.

    • 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.
        Specified by:
        getId in interface Entity
        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 NotFoundException being thrown.
      • 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
      • getRelationshipTypes

        Iterable<RelationshipType> getRelationshipTypes()
        Returns relationship types which this node has one more relationships for. If this node doesn't have any relationships an empty Iterable will be returned.
        Returns:
        relationship types which this node has one more relationships for.
      • getDegree

        int getDegree()
        Returns the number of relationships connected to this node regardless of direction or type. This operation is always O(1).
        Returns:
        the number of relationships connected to this node.
      • getDegree

        int getDegree(RelationshipType type)
        Returns the number of relationships of a given type connected to this node.
        Parameters:
        type - the type of relationships to get the degree for
        Returns:
        the number of relationships of a given type connected to this node.
      • getDegree

        int getDegree(Direction direction)
        Returns the number of relationships of a given direction connected to this node.
        Parameters:
        direction - the direction of the relationships
        Returns:
        the number of relationships of a given direction for this node.
      • getDegree

        int getDegree(RelationshipType type,
                      Direction direction)
        Returns the number of relationships of a given type and direction connected to this node.
        Parameters:
        type - the type of relationships to get the degree for
        direction - the direction of the relationships
        Returns:
        the number of relationships of a given type and direction for this node.
      • addLabel

        void addLabel(Label label)
        Adds a Label to this node. If this node doesn't already have this label it will be added. If it already has the label, nothing will happen.
        Parameters:
        label - the label to add to this node.
      • removeLabel

        void removeLabel(Label label)
        Removes a Label from this node. If this node doesn't have this label, nothing will happen.
        Parameters:
        label - the label to remove from this node.
      • hasLabel

        boolean hasLabel(Label label)
        Checks whether or not this node has the given label.
        Parameters:
        label - the label to check for.
        Returns:
        true if this node has the given label, otherwise false.
      • getLabels

        Iterable<Label> getLabels()
        Lists all labels attached to this node. If this node has no labels an empty Iterable will be returned.
        Returns:
        all labels attached to this node.

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