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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hadoop.mapreduce;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonFactoryBuilder;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import java.io.BufferedInputStream;
import java.io.IOException;
/**
* Simple JSON reader which splits the input file along JSON object boundaries.
*
* There are two cases handled here:
* 1. Each line contains a JSON object, i.e. { ... }
* 2. The file contains an array of objects with arbitrary line breaks, i.e. [ {...}, {...} ]
*
* Not suitable for cases where you want to extract objects from some other arbitrary structure.
*
* TODO: Support config which points to a array in the JSON as start point for object extraction,
* ala how it is done in VespaHttpClient.parseResultJson, i.e. support rootNode config.
*
* @author lesters
*/
public class VespaSimpleJsonInputFormat extends FileInputFormat<Text, NullWritable> {
@Override
public RecordReader<Text, NullWritable> createRecordReader(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
return new VespaJsonRecordReader();
}
public static class VespaJsonRecordReader extends RecordReader<Text, NullWritable> {
private long remaining;
private JsonParser parser;
private Text currentKey;
private NullWritable currentValue = NullWritable.get();
@Override
public void initialize(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
FileSplit fileSplit = (FileSplit) split;
FSDataInputStream stream = FileSystem.get(context.getConfiguration()).open(fileSplit.getPath());
if (fileSplit.getStart() != 0) {
stream.seek(fileSplit.getStart());
}
remaining = fileSplit.getLength();
JsonFactory factory = new JsonFactoryBuilder().disable(JsonFactory.Feature.CANONICALIZE_FIELD_NAMES).build();
parser = factory.createParser(new BufferedInputStream(stream));
parser.setCodec(new ObjectMapper());
parser.nextToken();
if (parser.currentToken() == JsonToken.START_ARRAY) {
parser.nextToken();
}
}
@Override
public boolean nextKeyValue() throws IOException, InterruptedException {
if (parser.currentToken() != JsonToken.START_OBJECT) {
return true;
}
currentKey = new Text(parser.readValueAsTree().toString());
parser.nextToken();
return false;
}
@Override
public Text getCurrentKey() throws IOException, InterruptedException {
return currentKey;
}
@Override
public NullWritable getCurrentValue() throws IOException, InterruptedException {
return currentValue;
}
@Override
public float getProgress() throws IOException, InterruptedException {
return parser.getCurrentLocation().getByteOffset() / remaining;
}
@Override
public void close() throws IOException {
parser.close();
}
}
}
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