001/** 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 019package org.apache.hadoop.mapreduce; 020 021import java.io.IOException; 022 023import org.apache.hadoop.classification.InterfaceAudience; 024import org.apache.hadoop.classification.InterfaceStability; 025 026/** 027 * A context object that allows input and output from the task. It is only 028 * supplied to the {@link Mapper} or {@link Reducer}. 029 * @param <KEYIN> the input key type for the task 030 * @param <VALUEIN> the input value type for the task 031 * @param <KEYOUT> the output key type for the task 032 * @param <VALUEOUT> the output value type for the task 033 */ 034@InterfaceAudience.Public 035@InterfaceStability.Evolving 036public interface TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT> 037 extends TaskAttemptContext { 038 039 /** 040 * Advance to the next key, value pair, returning null if at end. 041 * @return the key object that was read into, or null if no more 042 */ 043 public boolean nextKeyValue() throws IOException, InterruptedException; 044 045 /** 046 * Get the current key. 047 * @return the current key object or null if there isn't one 048 * @throws IOException 049 * @throws InterruptedException 050 */ 051 public KEYIN getCurrentKey() throws IOException, InterruptedException; 052 053 /** 054 * Get the current value. 055 * @return the value object that was read into 056 * @throws IOException 057 * @throws InterruptedException 058 */ 059 public VALUEIN getCurrentValue() throws IOException, InterruptedException; 060 061 /** 062 * Generate an output key/value pair. 063 */ 064 public void write(KEYOUT key, VALUEOUT value) 065 throws IOException, InterruptedException; 066 067 /** 068 * Get the {@link OutputCommitter} for the task-attempt. 069 * @return the <code>OutputCommitter</code> for the task-attempt 070 */ 071 public OutputCommitter getOutputCommitter(); 072}