hadoop KeyOnlyTextOutputReader 源码
haddop KeyOnlyTextOutputReader 代码
文件路径：/hadoop-tools/hadoop-streaming/src/main/java/org/apache/hadoop/streaming/io/KeyOnlyTextOutputReader.java
/**
* 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.streaming.io;
import java.io.DataInput;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.streaming.PipeMapRed;
import org.apache.hadoop.util.LineReader;
/**
* OutputReader that reads the client's output as text, interpreting each line
* as a key and outputting NullWritables for values.
*/
public class KeyOnlyTextOutputReader extends OutputReader<Text, NullWritable> {
private LineReader lineReader;
private byte[] bytes;
private DataInput clientIn;
private Configuration conf;
private Text key;
private Text line;
@Override
public void initialize(PipeMapRed pipeMapRed) throws IOException {
super.initialize(pipeMapRed);
clientIn = pipeMapRed.getClientInput();
conf = pipeMapRed.getConfiguration();
lineReader = new LineReader((InputStream)clientIn, conf);
key = new Text();
line = new Text();
}
@Override
public boolean readKeyValue() throws IOException {
if (lineReader.readLine(line) <= 0) {
return false;
}
bytes = line.getBytes();
key.set(bytes, 0, line.getLength());
line.clear();
return true;
}
@Override
public Text getCurrentKey() throws IOException {
return key;
}
@Override
public NullWritable getCurrentValue() throws IOException {
return NullWritable.get();
}
@Override
public String getLastOutput() {
if (bytes != null) {
try {
return new String(bytes, "UTF-8");
} catch (UnsupportedEncodingException e) {
return "<undecodable>";
}
} else {
return null;
}
}
}
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