001/* 002 * Copyright (c) 2016-2017 Chris K Wensel. 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 021package cascading.nested.core; 022 023import cascading.flow.FlowProcess; 024import cascading.operation.Aggregator; 025import cascading.operation.AggregatorCall; 026import cascading.operation.OperationCall; 027import cascading.tuple.Fields; 028import cascading.tuple.Tuple; 029import cascading.tuple.TupleEntry; 030import heretical.pointer.operation.Builder; 031 032/** 033 * Class NestedBaseBuildAggregator is the base class for {@link Aggregator} implementations that rely on the 034 * {@link BuildSpec} class when declaring transformations on nested object types. 035 * <p> 036 * Specifically, {@code *BuildAsAggregator} and {@code *BuildIntoAggregator} classes create or update (respectively) 037 * nested object types from Aggregator argument {@link Fields} where the field values can be primitive types, objects 038 * (with a corresponding {@link cascading.tuple.type.CoercibleType}), or themselves nest object types. 039 * <p> 040 * In the case of a {@code *BuildIntoAggregator} the last argument in the {@code arguments} {@link TupleEntry} will be 041 * the object the BuildSpec copies values into. 042 * <p> 043 * In the case of a {@code *BuildAsAggregator} a new root object will be created for the BuildSpec to copy values into. 044 * <p> 045 * In the case of JSON objects, multiple JSON objects selected as arguments can be combined into a new JSON object 046 * by mapping the field names into locations on the new object. 047 * 048 * @see BuildSpec 049 */ 050public abstract class NestedBaseBuildAggregator<Node, Result> extends NestedSpecBaseOperation<Node, Result, NestedBaseBuildAggregator<Node, Result>.Context> implements Aggregator<NestedBaseBuildAggregator<Node, Result>.Context> 051 { 052 public class Context 053 { 054 Node rootNode = null; 055 056 public void reset() 057 { 058 rootNode = getResultNode( null ); 059 } 060 } 061 062 protected Builder<Node, Result> builder; 063 064 public NestedBaseBuildAggregator( NestedCoercibleType<Node, Result> nestedCoercibleType, Fields fieldDeclaration, BuildSpec... buildSpecs ) 065 { 066 super( nestedCoercibleType, fieldDeclaration ); 067 this.builder = new Builder<>( nestedCoercibleType.getNestedPointerCompiler(), buildSpecs ); 068 } 069 070 @Override 071 public void prepare( FlowProcess flowProcess, OperationCall<Context> operationCall ) 072 { 073 operationCall.setContext( new Context() ); 074 } 075 076 @Override 077 public void start( FlowProcess flowProcess, AggregatorCall<Context> aggregatorCall ) 078 { 079 aggregatorCall.getContext().reset(); 080 081 Node rootNode = aggregatorCall.getContext().rootNode; 082 083 builder.buildLiterals( rootNode ); 084 } 085 086 @Override 087 public void aggregate( FlowProcess flowProcess, AggregatorCall<Context> aggregatorCall ) 088 { 089 TupleEntry arguments = aggregatorCall.getArguments(); 090 091 Node rootNode = aggregatorCall.getContext().rootNode; 092 093 builder.build( arguments::getObject, rootNode ); 094 } 095 096 @Override 097 public void complete( FlowProcess flowProcess, AggregatorCall<Context> aggregatorCall ) 098 { 099 aggregatorCall.getOutputCollector().add( new Tuple( aggregatorCall.getContext().rootNode ) ); 100 } 101 }