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.flow.FlowProcess; 025import cascading.tuple.TupleEntry; 026 027/** 028 * Class GroupAssertion is a kind of {@link Assertion} used with the {@link cascading.pipe.Every} pipe Operator. 029 * <p> 030 * Implementers should also extend {@link BaseOperation}. 031 * 032 * @see Aggregator 033 */ 034public interface GroupAssertion<C> extends Assertion<C> 035 { 036 /** 037 * Method start initializes the aggregation procedure and is called for every unique grouping. 038 * <p> 039 * The AggregatorCall context should be initialized here if necessary. 040 * <p> 041 * The first time this method is called for a given 'process', the AggregatorCall context will be null. This method should 042 * set a new instance of the user defined context object. When the AggregatorCall context is not null, it is up to 043 * the developer to create a new instance, or 'recycle' the given instance. If recycled, it must be re-initialized to 044 * remove any previous state/values. 045 * <p> 046 * For example, if a Map is used to hold the intermediate data for each subsequent 047 * {@link #aggregate(cascading.flow.FlowProcess, GroupAssertionCall)} call, 048 * new HashMap() should be set on the AggregatorCall instance when {@link cascading.operation.AggregatorCall#getContext()} is null. 049 * On the next grouping, start() will be called again, but this time with the old Map instance. In this case, 050 * map.clear() should be invoked before returning. 051 * 052 * @param flowProcess of type FlowProcess 053 * @param assertionCall of type GroupAssertionCall 054 */ 055 void start( FlowProcess flowProcess, GroupAssertionCall<C> assertionCall ); 056 057 /** 058 * Method aggregate is called for each {@link TupleEntry} value in the current grouping. 059 * 060 * @param flowProcess of type FlowProcess 061 * @param assertionCall of type GroupAssertionCall 062 */ 063 void aggregate( FlowProcess flowProcess, GroupAssertionCall<C> assertionCall ); 064 065 /** 066 * Method doAssert performs the assertion. 067 * 068 * @param flowProcess of type FlowProcess 069 * @param assertionCall of type GroupAssertionCall 070 */ 071 void doAssert( FlowProcess flowProcess, GroupAssertionCall<C> assertionCall ); 072 073 }