| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.hadoop.mapreduce; |
| |
| import java.io.Closeable; |
| import java.io.IOException; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * The record reader breaks the data into key/value pairs for input to the |
| * {@link Mapper}. |
| * @param <KEYIN> |
| * @param <VALUEIN> |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Stable |
| public abstract class RecordReader<KEYIN, VALUEIN> implements Closeable { |
| |
| /** |
| * Called once at initialization. |
| * @param split the split that defines the range of records to read |
| * @param context the information about the task |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| public abstract void initialize(InputSplit split, |
| TaskAttemptContext context |
| ) throws IOException, InterruptedException; |
| |
| /** |
| * Read the next key, value pair. |
| * @return true if a key/value pair was read |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| public abstract |
| boolean nextKeyValue() throws IOException, InterruptedException; |
| |
| /** |
| * Get the current key |
| * @return the current key or null if there is no current key |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| public abstract |
| KEYIN getCurrentKey() throws IOException, InterruptedException; |
| |
| /** |
| * Get the current value. |
| * @return the object that was read |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| public abstract |
| VALUEIN getCurrentValue() throws IOException, InterruptedException; |
| |
| /** |
| * The current progress of the record reader through its data. |
| * @return a number between 0.0 and 1.0 that is the fraction of the data read |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| public abstract float getProgress() throws IOException, InterruptedException; |
| |
| /** |
| * Close the record reader. |
| */ |
| public abstract void close() throws IOException; |
| } |