| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.tinkerpop.gremlin.structure; |
| |
| import java.util.Iterator; |
| |
| /** |
| * An {@link Edge} links two {@link Vertex} objects. Along with its {@link Property} objects, an {@link Edge} has both |
| * a {@link Direction} and a {@code label}. The {@link Direction} determines which {@link Vertex} is the tail |
| * {@link Vertex} (out {@link Vertex}) and which {@link Vertex} is the head {@link Vertex} |
| * (in {@link Vertex}). The {@link Edge} {@code label} determines the type of relationship that exists between the |
| * two vertices. |
| * <p/> |
| * Diagrammatically: |
| * <pre> |
| * outVertex ---label---> inVertex. |
| * </pre> |
| * |
| * @author Marko A. Rodriguez (http://markorodriguez.com) |
| * @author Stephen Mallette (http://stephen.genoprime.com) |
| */ |
| public interface Edge extends Element { |
| |
| /** |
| * The default label to use for an edge. |
| * This is typically never used as when an edge is created, an edge label is required to be specified. |
| */ |
| public static final String DEFAULT_LABEL = "edge"; |
| |
| /** |
| * Retrieve the vertex (or vertices) associated with this edge as defined by the direction. |
| * If the direction is {@link Direction#BOTH} then the iterator order is: {@link Direction#OUT} then {@link Direction#IN}. |
| * |
| * @param direction Get the incoming vertex, outgoing vertex, or both vertices |
| * @return An iterator with 1 or 2 vertices |
| */ |
| public Iterator<Vertex> vertices(final Direction direction); |
| |
| /** |
| * Get the outgoing/tail vertex of this edge. |
| * |
| * @return the outgoing vertex of the edge |
| */ |
| public default Vertex outVertex() { |
| return this.vertices(Direction.OUT).next(); |
| } |
| |
| /** |
| * Get the incoming/head vertex of this edge. |
| * |
| * @return the incoming vertex of the edge |
| */ |
| public default Vertex inVertex() { |
| return this.vertices(Direction.IN).next(); |
| } |
| |
| /** |
| * Get both the outgoing and incoming vertices of this edge. |
| * The first vertex in the iterator is the outgoing vertex. |
| * The second vertex in the iterator is the incoming vertex. |
| * |
| * @return an iterator of the two vertices of this edge |
| */ |
| public default Iterator<Vertex> bothVertices() { |
| return this.vertices(Direction.BOTH); |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public <V> Iterator<Property<V>> properties(final String... propertyKeys); |
| |
| |
| /** |
| * Common exceptions to use with an edge. |
| */ |
| public static class Exceptions extends Element.Exceptions { |
| |
| private Exceptions() { |
| } |
| |
| public static UnsupportedOperationException userSuppliedIdsNotSupported() { |
| return new UnsupportedOperationException("Edge does not support user supplied identifiers"); |
| } |
| |
| public static UnsupportedOperationException userSuppliedIdsOfThisTypeNotSupported() { |
| return new UnsupportedOperationException("Edge does not support user supplied identifiers of this type"); |
| } |
| |
| public static IllegalStateException edgeRemovalNotSupported() { |
| return new IllegalStateException("Edge removal are not supported"); |
| } |
| } |
| } |