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 }