Apache kafka sending java object failed

Question

I have this object

       HashMap message = new HashMap();
       message.put("x", "xxxxx");
       message.put("y", "yyyyy");
       message.put("z", 100);

       ProducerRecord producerRecord = new ProducerRecord(topic, message);
       producer.send(producerRecord);

I am getting

Exception in thread "main" org.apache.kafka.common.errors.SerializationException: Can't convert value of class java.util.HashMap to class org.apache.kafka.common.serialization.StringSerializer specified in value.serializer

Nikem · Accepted Answer · 2016-05-28 18:17:38Z

4

You have to provide Kafka with a way how to convert you messages, in this case HashMap, into binary form. From the Kafka documentation:

The key.serializer and value.serializer instruct how to turn the key and value objects the user provides with their ProducerRecord into bytes. You can use the included ByteArraySerializer or StringSerializer for simple string or byte types.

The example of usage:

 Properties props = new Properties();
 props.put("key.serializer", "YourImplementation");
 props.put("value.serializer", "YourImplementation");

 Producer<String, HashMap> producer = new KafkaProducer<>(props);

answered May 28, 2016 at 18:17

Nikem

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2 Comments

Manish Kumar Over a year ago

a simple example will be nice

Sankalp Over a year ago

I get the error org.apache.kafka.common.errors.SerializationException: Can't convert value of class java.util.HashMap to class org.apache.kafka.common.serialization.ByteArraySerializer specified in value.serializer

sarjit07 · Accepted Answer · 2018-01-16 12:16:07Z

1

You can convert the Hashmap into json and use JsonSerializer as

private void configureProducer() {
    Properties props = new Properties();
    props.put("key.serializer", StringSerializer.class.getName());
    props.put("value.serializer", JsonSerializer.class.getName());
    producer = new KafkaProducer<String, String>(props);
}

Or You can also use ByteArraySerializer. Refer this

answered Jan 16, 2018 at 12:16

sarjit07

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