Implementing a CustomTransformer in Java

[Mathieu Pedrero]

Hi Everyone,

I need some help. I would like to implement a CustomTransformer in java, but the related section of the NN API documentation is still empty.

I would like to build a transformer (DataStream Transformer for Flink), equivalement to the map DataStream Flink API, that would create some complex object (from a template, for example) from input datas selected by the NN user (more or less as the mapVariable transformer works).

I tried to start by analyzing the sources of an existing CustomTransformer (UnionTransformer), but i'm not very "fluent" in scala, and that's not so easy to me.

Could you help me ? Is there some Java examples of advanced API implementation ?

Thanks a lot, and best regards.

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Mathieu

[arek.b...@gmail.com]

Hi Mathieu,

We have a javademo model here: https://github.com/TouK/nussknacker/blob/master/engine/demo/src/main/java/pl/touk/nussknacker/engine/javademo/DemoProcessConfigCreator.java

It provides two java custom transformers:

- https://github.com/TouK/nussknacker/blob/master/engine/demo/src/main/java/pl/touk/nussknacker/engine/javademo/EventsCounter.java

- https://github.com/TouK/nussknacker/blob/master/engine/demo/src/main/java/pl/touk/nussknacker/engine/javademo/TransactionAmountAggregator.java

Basically the main thing that you need is to write a class implementing CustomStreamTransformer with method annotated by @MethodToInvoke. This method should return Flink's data stream transformation wrapped with JavaFlinkCustomStreamTransformation.apply().

At the end you need to return instance of this class from your model's customStreamTransformers registry located in implementation of your ProcessConfigCreator.

Does my answer help you figuring out what is needed to do?

Arek

[Mathieu Pedrero]

Hi,

Thanks for the information. It looks promising. I'll try this later today.

Best regards,

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