001/*
002 * Copyright (c) 2007-2016 Concurrent, Inc. All Rights Reserved.
003 *
004 * Project and contact information: http://www.cascading.org/
005 *
006 * This file is part of the Cascading project.
007 *
008 * Licensed under the Apache License, Version 2.0 (the "License");
009 * you may not use this file except in compliance with the License.
010 * You may obtain a copy of the License at
011 *
012 *     http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing, software
015 * distributed under the License is distributed on an "AS IS" BASIS,
016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017 * See the License for the specific language governing permissions and
018 * limitations under the License.
019 */
020
021package cascading.flow.stream.duct;
022
023import cascading.flow.stream.graph.StreamGraph;
024
025/**
026 *
027 */
028public abstract class Duct<Incoming, Outgoing>
029  {
030  protected Duct<Outgoing, ?> next;
031  protected Integer ordinal;
032
033  Duct()
034    {
035    }
036
037  Duct( Duct<Outgoing, ?> next )
038    {
039    this.next = next;
040    }
041
042  public Duct getNext()
043    {
044    return next;
045    }
046
047  public void bind( StreamGraph streamGraph )
048    {
049    next = getNextFor( streamGraph );
050    }
051
052  protected Duct getNextFor( StreamGraph streamGraph )
053    {
054    return streamGraph.createNextFor( this );
055    }
056
057  /** Called immediately after bind */
058  public void initialize()
059    {
060    }
061
062  /**
063   *
064   */
065  public void prepare()
066    {
067    // never chain prepare calls
068    }
069
070  public final void receiveFirst( Incoming incoming )
071    {
072    receive( null, incoming );
073    }
074
075  public void start( Duct previous )
076    {
077    next.start( this );
078    }
079
080  public abstract void receive( Duct previous, Incoming incoming );
081
082  public void complete( Duct previous )
083    {
084    next.complete( this );
085    }
086
087  public void cleanup()
088    {
089    // never chain cleanup calls
090    }
091
092  @Override
093  public String toString()
094    {
095    return getClass().getSimpleName();
096    }
097  }