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 }