Re: Java types

Posted by Timo Walther on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Java-types-tp17717p17721.html

Hi Boris,

each API is designed language-specific so they might not always be the same. Scala has better type extraction features and let you write code very precisely. Java requires sometime more code to archieve the same.

You don't need to specify the type in .flatMap() explicitly. It will be automatically extracted using the generic signature of DataDataConverter.

Regarding your error. Make sure that you don't mix up the API classes. If you want to use the Java API you should not use "org.apache.flink.streaming.api.scala.DataStream" but the Java one.

Regards,
Timo



Am 1/11/18 um 5:13 AM schrieb Boris Lublinsky:

More questions

In Scala my DataProcessor is defined as

class DataProcessorKeyed extends CoProcessFunction[WineRecord, ModelToServe, Double] with CheckpointedFunction {

And it is used as follows

val models = modelsStream.map(ModelToServe.fromByteArray(_))
  .flatMap(BadDataHandler[ModelToServe])
  .keyBy(_.dataType)
val data = dataStream.map(DataRecord.fromByteArray(_))
  .flatMap(BadDataHandler[WineRecord])
  .keyBy(_.dataType)

// Merge streams
data
  .connect(models)
  .process(DataProcessorKeyed())

When I am doing the same thing in Java

public class DataProcessorKeyed extends CoProcessFunction<Winerecord.WineRecord, ModelToServe, Double> implements CheckpointedFunction{

Which I am using as follows

// Read data from streams
DataStream<Tuple2<String, ModelToServe>> models = modelsStream
        .flatMap(new ModelDataConverter(), new TupleTypeInfo<>(BasicTypeInfo.STRING_TYPE_INFO, TypeInformation.of(ModelToServe.class)))
        .keyBy(0);
DataStream<Tuple2<String, Winerecord.WineRecord>> data = dataStream
        .flatMap(new DataDataConverter(), new TupleTypeInfo<>(BasicTypeInfo.STRING_TYPE_INFO, TypeInformation.of(Winerecord.WineRecord.class)))
        .keyBy(0);

// Merge streams
data
        .connect(models)
        .process(new DataProcessorKeyed());

I am getting an error

Error:(68, 17) java: no suitable method found for keyBy(int)

    method org.apache.flink.streaming.api.scala.DataStream.keyBy(scala.collection.Seq<java.lang.Object>) is not applicable

      (argument mismatch; int cannot be converted to scala.collection.Seq<java.lang.Object>)

    method org.apache.flink.streaming.api.scala.DataStream.<K>keyBy(scala.Function1<org.apache.flink.api.java.tuple.Tuple2<java.lang.String,com.lightbend.model.ModelToServe>,K>,org.apache.flink.api.common.typeinfo.TypeInformation<K>) is not applicable

      (cannot infer type-variable(s) K

        (actual and formal argument lists differ in length))

So it assumes key/value pairs for the coprocessor

Why is such difference between APIs?

Boris Lublinsky
FDP Architect
[hidden email]
https://www.lightbend.com/

On Jan 10, 2018, at 6:20 PM, Boris Lublinsky <[hidden email]> wrote:

I am trying to covert Scala code (which works fine) to Java

The sacral code is:

// create a Kafka consumers
// Data
val dataConsumer = new FlinkKafkaConsumer010[Array[Byte]](
  DATA_TOPIC,
  new ByteArraySchema,
  dataKafkaProps
)

// Model
val modelConsumer = new FlinkKafkaConsumer010[Array[Byte]](
  MODELS_TOPIC,
  new ByteArraySchema,
  modelKafkaProps
)

// Create input data streams
val modelsStream = env.addSource(modelConsumer)
val dataStream = env.addSource(dataConsumer)

// Read data from streams
val models = modelsStream.map(ModelToServe.fromByteArray(_))
  .flatMap(BadDataHandler[ModelToServe])
  .keyBy(_.dataType)
val data = dataStream.map(DataRecord.fromByteArray(_))
  .flatMap(BadDataHandler[WineRecord])
  .keyBy(_.dataType)

Now I am trying to re write it to Java and fighting with the requirement of providing types, where they should be obvious

// create a Kafka consumers
// Data
FlinkKafkaConsumer010<byte[]> dataConsumer = new FlinkKafkaConsumer010<>(
        ModelServingConfiguration.DATA_TOPIC,
        new ByteArraySchema(),
        dataKafkaProps);

// Model
FlinkKafkaConsumer010<byte[]>  modelConsumer = new FlinkKafkaConsumer010<>(
        ModelServingConfiguration.MODELS_TOPIC,
        new ByteArraySchema(),
        modelKafkaProps);

// Create input data streams
DataStream<byte[]> modelsStream = env.addSource(modelConsumer, PrimitiveArrayTypeInfo.BYTE_PRIMITIVE_ARRAY_TYPE_INFO);
DataStream<byte[]> dataStream = env.addSource(dataConsumer, PrimitiveArrayTypeInfo.BYTE_PRIMITIVE_ARRAY_TYPE_INFO);
// Read data from streams
DataStream<Tuple2<String,ModelToServe>> models = modelsStream
     .flatMap(new ModelConverter(), new TupleTypeInfo<>(BasicTypeInfo.STRING_TYPE_INFO, TypeInformation.of(ModelToServe.class)));

Am I missing something similar to import org.apache.flink.api.scala._

 In java?

Now if this is an only way, Does this seems right?

Boris Lublinsky
FDP Architect
[hidden email]
https://www.lightbend.com/