Flink: Unresolved compilation problem (valueOnly is not applicable for the arguments (Class<NumberDeserializers.IntegerDeserializer>))

Question

I want to setup a program where I can send a data stream with kafka to flink.

    DataStream<Integer> input =
            env.fromSource(
                    KafkaSource.<Integer>builder()
                            .setBootstrapServers(
                                    parameterTool
                                            .getProperties()
                                            .getProperty(
                                                    ProducerConfig.BOOTSTRAP_SERVERS_CONFIG))
                            .setBounded(OffsetsInitializer.latest())
                            .setDeserializer(
                                    KafkaRecordDeserializationSchema.valueOnly(
                                            IntegerDeserializer.class))
                            .setTopics(parameterTool.getRequired("input-topic"))
                            .build(),
                    WatermarkStrategy.noWatermarks(),
                    "kafka-source");

When I try to compile the code above the following failure occurs:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    The method valueOnly(DeserializationSchema<V>) in the type KafkaRecordDeserializationSchema is not applicable for the arguments (Class<NumberDeserializers.IntegerDeserializer>)

There is a problem with the valueOnly, but I don't get what the problem is and how to solve.

Answer 1

Perhaps you picked up the wrong imports.

I think perhaps you wanted org.apache.kafka.common.serialization.IntegerDeserializer rather than the IntegerDeserializer from Jackson. The class you pass to valueOnly should implement org.apache.kafka.common.serialization.Deserializer.