我身上发生了一件神秘事:
我想做什么:
1. Save a Protocol Buffers object as SequenceFile format.
2. Read this SequenceFile text and extract the field that I need.
神秘的部分是: 我想要检索的一个字段始终为空。
Product_Perf
是我想从SequencFiles中提取的字段,总是丢失。
这是我的协议缓冲模式:
message ProductJoin {
Signals signals = 1;
int64 id = 2;
}
message Signals {
ProductPerf product_perf = 1;
}
message ProductPerf {
int64 impressions = 1;
}
以下是我将协议缓冲区保存为SequenceFiles的方法:
JavaPairRDD<BytesWritable, BytesWritable> bytesWritableJavaPairRdd =
flattenedPjPairRdd.mapToPair(
new PairFunction<Tuple2<Long, ProductJoin>, BytesWritable, BytesWritable>() {
@Override
public Tuple2<BytesWritable, BytesWritable> call(Tuple2<Long, ProductJoin> longProductJoinTuple2) throws Exception {
return new Tuple2<>(
new BytesWritable(longProductJoinTuple2._2().getId().getBytes()),
new BytesWritable(longProductJoinTuple2._2().toByteArray()));
}
}
//dump SequenceFiles
bytesWritableJavaPairRdd.saveAsHadoopFile(
"/tmp/path/",
BytesWritable.class,
BytesWritable.class,
SequenceFileOutputFormat.class
);
以下是我如何阅读SequenceFile的代码:
sparkSession.sparkContext()
.sequenceFile("tmp/path", BytesWritable.class, BytesWritable.class)
.toJavaRDD()
.mapToPair(
bytesWritableBytesWritableTuple2 -> {
Method parserMethod = clazz.getDeclaredMethod("parser");
Parser<T> parser = (Parser<T>) parserMethod.invoke(null);
return new Tuple2<>(
Text.decode(bytesWritableBytesWritableTuple2._1().getBytes()),
parser.parseFrom(bytesWritableBytesWritableTuple2._2().getBytes()));
}
);