001/*
002 * Copyright (c) 2007-2015 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
032  Duct()
033    {
034    }
035
036  Duct( Duct<Outgoing, ?> next )
037    {
038    this.next = next;
039    }
040
041  public Duct getNext()
042    {
043    return next;
044    }
045
046  public void bind( StreamGraph streamGraph )
047    {
048    next = getNextFor( streamGraph );
049    }
050
051  protected Duct getNextFor( StreamGraph streamGraph )
052    {
053    return streamGraph.createNextFor( this );
054    }
055
056  /** Called immediately after bind */
057  public void initialize()
058    {
059    }
060
061  /**
062   *
063   */
064  public void prepare()
065    {
066    // never chain prepare calls
067    }
068
069  public final void receiveFirst( Incoming incoming )
070    {
071    receive( null, incoming );
072    }
073
074  public void start( Duct previous )
075    {
076    next.start( this );
077    }
078
079  public abstract void receive( Duct previous, Incoming incoming );
080
081  public void complete( Duct previous )
082    {
083    next.complete( this );
084    }
085
086  public void cleanup()
087    {
088    // never chain cleanup calls
089    }
090
091  @Override
092  public String toString()
093    {
094    return getClass().getSimpleName();
095    }
096  }