is JSONDeserializationSchema() deprecated in Flink?

Question

I am new to Flink and doing something very similar to the below link.

Cannot see message while sinking kafka stream and cannot see print message in flink 1.2

I am also trying to add JSONDeserializationSchema() as a deserializer for my Kafka input JSON message which is without a key.

But I found JSONDeserializationSchema() is not present.

Please let me know if I am doing anything wrong.

Answer 1

JSONDeserializationSchema was removed in Flink 1.8, after having been deprecated earlier.

The recommended approach is to write a deserializer that implements DeserializationSchema<T>. Here's an example, which I've copied from the Flink Operations Playground:

import org.apache.flink.api.common.serialization.DeserializationSchema;
import org.apache.flink.api.common.typeinfo.TypeInformation;

import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;

/**
 * A Kafka {@link DeserializationSchema} to deserialize {@link ClickEvent}s from JSON.
 *
 */
public class ClickEventDeserializationSchema implements DeserializationSchema<ClickEvent> {

    private static final long serialVersionUID = 1L;

    private static final ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public ClickEvent deserialize(byte[] message) throws IOException {
        return objectMapper.readValue(message, ClickEvent.class);
    }

    @Override
    public boolean isEndOfStream(ClickEvent nextElement) {
        return false;
    }

    @Override
    public TypeInformation<ClickEvent> getProducedType() {
        return TypeInformation.of(ClickEvent.class);
    }
}

For a Kafka producer you'll want to implement KafkaSerializationSchema<T>, and you'll find examples of that in that same project.