001/* 002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved. 003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved. 004 * 005 * Project and contact information: http://www.cascading.org/ 006 * 007 * This file is part of the Cascading project. 008 * 009 * Licensed under the Apache License, Version 2.0 (the "License"); 010 * you may not use this file except in compliance with the License. 011 * You may obtain a copy of the License at 012 * 013 * http://www.apache.org/licenses/LICENSE-2.0 014 * 015 * Unless required by applicable law or agreed to in writing, software 016 * distributed under the License is distributed on an "AS IS" BASIS, 017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 018 * See the License for the specific language governing permissions and 019 * limitations under the License. 020 */ 021 022package cascading.flow; 023 024import java.util.List; 025import java.util.Map; 026 027import cascading.pipe.Pipe; 028 029/** 030 * Interface AssemblyPlanner is used to allow for lazy evaluation of a pipe assembly during planning of a {@link Flow}. 031 * <p> 032 * This allows for new languages or frameworks that may require additional meta-data from the 033 * underlying platform or environment. Specifically field names and type information from incoming source 034 * and outgoing sink {@link cascading.tap.Tap}s. 035 * <p> 036 * AssemblyPlanner implementations are handed to a {@link cascading.flow.planner.FlowPlanner} 037 * instance in the order they should be evaluated. 038 * Every instance has the opportunity to replace any prior tails with new branches and paths. 039 * <p> 040 * Every instance of AssemblyPlanner evaluated is given the current {@link FlowDef} used on the current 041 * {@link FlowConnector}, the current Flow instance (only initialized with source and sink Taps provided by the 042 * FlowDef), and the tails provided by the FlowDef or those returned by prior AssemblyPlanner instances. 043 * <p> 044 * An AssemblyPlanner cannot change or modify the Flow, or change out any Taps used as sources, sinks, traps, or 045 * checkpoints. 046 * <p> 047 * This is an experimental API and subject to change without notice. 048 */ 049public interface AssemblyPlanner 050 { 051 interface Context 052 { 053 FlowDef getFlowDef(); 054 055 Flow getFlow(); 056 057 List<Pipe> getTails(); 058 } 059 060 /** 061 * Called when this AssemblyPlanner instance should return any additional tail Pipe instances for used 062 * when completing the Flow plan. 063 * 064 * @param context parameter object of the Context 065 * @return tail Pipe instances to replace the given tails 066 */ 067 List<Pipe> resolveTails( Context context ); 068 069 /** 070 * Returns a map of properties giving more details about the Flow object. This can be picked up by a Flow object and 071 * added to its internal FlowDescriptor. 072 * 073 * @return Map 074 */ 075 Map<String, String> getFlowDescriptor(); 076 }