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.operation; 023 024import cascading.tuple.Fields; 025import cascading.tuple.TupleEntry; 026import cascading.tuple.TupleEntryCollector; 027 028/** 029 * Interface AggregatorCall provides access to the current {@link Aggregator} invocation arguments. 030 * <p> 031 * This interface is generic, allowing the user to set a custom 'context' object when {@link Aggregator#start(cascading.flow.FlowProcess, AggregatorCall)} 032 * is called. The {@link OperationCall#setContext(Object)} and {@link OperationCall#getContext()} methods are 033 * inherited from {@link OperationCall}. 034 * 035 * @see Aggregator 036 * @see OperationCall 037 */ 038public interface AggregatorCall<C> extends OperationCall<C> 039 { 040 /** 041 * Returns the current grouping {@link TupleEntry}. 042 * 043 * @return TupleEntry 044 */ 045 TupleEntry getGroup(); 046 047 /** 048 * Returns {@link TupleEntry} of argument values. 049 * <p> 050 * Will return {@code null} unless called in {@link Aggregator#aggregate(cascading.flow.FlowProcess, AggregatorCall)}. 051 * <p> 052 * Note that the returned TupleEntry should not be cached (stored in a Collection), nor should the underlying Tuple 053 * instance. Where possible Cascading will re-use both TupleEntry and Tuple instances. 054 * <p> 055 * To get a safe copy that can be cached, use {@link TupleEntry#getTupleCopy()}. 056 * 057 * @return TupleEntry 058 */ 059 TupleEntry getArguments(); 060 061 /** 062 * Return the resolved {@link cascading.tuple.Fields} declared by the current {@link Operation}. 063 * 064 * @return Fields 065 */ 066 Fields getDeclaredFields(); 067 068 /** 069 * Returns the {@link cascading.tuple.TupleEntryCollector} used to emit result values. 070 * <p> 071 * Will return {@code null} unless called in {@link Aggregator#complete(cascading.flow.FlowProcess, AggregatorCall)}. 072 * 073 * @return TupleCollector 074 */ 075 TupleEntryCollector getOutputCollector(); 076 }