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.Function; 025import cascading.operation.FunctionCall; 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 NestedBaseBuildFunction is the base class for {@link Function} implementations that rely on the 034 * {@link BuildSpec} class when declaring transformations on nested object types. 035 * <p> 036 * Specifically, {@code *BuildAsFunction} and {@code *BuildIntoFunction} classes create or update (respectively) 037 * nested object types from Function 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 *BuildIntoFunction} 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 *BuildAsFunction} 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 * <p> 048 * For selecting the values from an existing nested object in order to create a new object or update an existing one 049 * see {@link NestedBaseCopyFunction} sub-classes. 050 * 051 * @see BuildSpec 052 */ 053public abstract class NestedBaseBuildFunction<Node, Result> extends NestedSpecBaseOperation<Node, Result, NestedBaseBuildFunction.Context> implements Function<NestedBaseBuildFunction.Context> 054 { 055 protected static class Context 056 { 057 public Tuple result; 058 059 public Context( Tuple result ) 060 { 061 this.result = result; 062 } 063 } 064 065 protected Builder<Node, Result> builder; 066 067 public NestedBaseBuildFunction( NestedCoercibleType<Node, Result> nestedCoercibleType, Fields fieldDeclaration, BuildSpec... buildSpecs ) 068 { 069 super( nestedCoercibleType, fieldDeclaration ); 070 this.builder = new Builder( nestedCoercibleType.getNestedPointerCompiler(), buildSpecs ); 071 } 072 073 @Override 074 public void prepare( FlowProcess flowProcess, OperationCall<Context> operationCall ) 075 { 076 operationCall.setContext( new Context( Tuple.size( 1 ) ) ); 077 } 078 079 @Override 080 public void operate( FlowProcess flowProcess, FunctionCall<Context> functionCall ) 081 { 082 Node rootNode = getResultNode( functionCall ); 083 084 TupleEntry arguments = functionCall.getArguments(); 085 086 builder.build( arguments::getObject, rootNode ); 087 088 Context context = functionCall.getContext(); 089 090 context.result.set( 0, rootNode ); 091 092 functionCall.getOutputCollector().add( context.result ); 093 } 094 }