001 /* 002 * Copyright (c) 2007-2014 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; 022 023 import java.util.List; 024 025 import cascading.pipe.Pipe; 026 027 /** 028 * Interface AssemblyPlanner is used to allow for lazy evaluation of a pipe assembly during planning of a {@link Flow}. 029 * <p/> 030 * This allows for new languages or frameworks that may require additional meta-data from the 031 * underlying platform or environment. Specifically field names and type information from incoming source 032 * and outgoing sink {@link cascading.tap.Tap}s. 033 * <p/> 034 * AssemblyPlanner implementations are handed to a {@link cascading.flow.planner.FlowPlanner} 035 * instance in the order they should be evaluated. 036 * Every instance has the opportunity to replace any prior tails with new branches and paths. 037 * <p/> 038 * Every instance of AssemblyPlanner evaluated is given the current {@link FlowDef} used on the current 039 * {@link FlowConnector}, the current Flow instance (only initialized with source and sink Taps provided by the 040 * FlowDef), and the tails provided by the FlowDef or those returned by prior AssemblyPlanner instances. 041 * <p/> 042 * An AssemblyPlanner cannot change or modify the Flow, or change out any Taps used as sources, sinks, traps, or 043 * checkpoints. 044 * <p/> 045 * This is an experimental API and subject to change without notice. 046 */ 047 public interface AssemblyPlanner 048 { 049 interface Context 050 { 051 FlowDef getFlowDef(); 052 053 Flow getFlow(); 054 055 List<Pipe> getTails(); 056 } 057 058 /** 059 * Called when this AssemblyPlanner instance should return any additional tail Pipe instances for used 060 * when completing the Flow plan. 061 * 062 * @param context parameter object of the Context 063 * @return tail Pipe instances to replace the given tails 064 */ 065 List<Pipe> resolveTails( Context context ); 066 }