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 */ 020 021 package cascading.flow.stream; 022 023 /** 024 * 025 */ 026 public abstract class Duct<Incoming, Outgoing> 027 { 028 protected Duct<Outgoing, ?> next; 029 030 Duct() 031 { 032 } 033 034 Duct( Duct<Outgoing, ?> next ) 035 { 036 this.next = next; 037 } 038 039 public Duct getNext() 040 { 041 return next; 042 } 043 044 public void bind( StreamGraph streamGraph ) 045 { 046 next = getNextFor( streamGraph ); 047 } 048 049 protected Duct getNextFor( StreamGraph streamGraph ) 050 { 051 return streamGraph.createNextFor( this ); 052 } 053 054 /** Called immediately after bind */ 055 public void initialize() 056 { 057 } 058 059 /** 060 * 061 */ 062 public void prepare() 063 { 064 // never chain prepare calls 065 } 066 067 public final void receiveFirst( Incoming incoming ) 068 { 069 receive( null, incoming ); 070 } 071 072 public void start( Duct previous ) 073 { 074 next.start( this ); 075 } 076 077 public abstract void receive( Duct previous, Incoming incoming ); 078 079 public void complete( Duct previous ) 080 { 081 next.complete( this ); 082 } 083 084 public void cleanup() 085 { 086 // never chain cleanup calls 087 } 088 089 @Override 090 public String toString() 091 { 092 return getClass().getSimpleName(); 093 } 094 }