When set ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG to IntegerSerializer in ProducerConfigs in Spring boot kafka, it gives class cast exception - spring-boot

Question

I m using this Spring boot with kafka
to setup my project. but when i run it it will give org.apache.kafka.common.errors.SerializationException: Can't convert key of class java.lang.Integer to class org.apache.kafka.common.serialization.StringSerializer specified in key.serializer
Caused by: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
this exception when send the request using kafka template.
#EmbeddedKafka(partitions = 1)
#SpringBootTest
class KafkaApplicationTests {
#Autowired
private MyKafkaListener listener;
#Autowired
private KafkaTemplate<Integer, String> template;
#Autowired
private EmbeddedKafkaBroker embeddedKafka;
#Test
public void testSimple() throws Exception {
template.send("annotated1", 0, "foo");
template.flush();
assertTrue(this.listener.latch1.await(10, TimeUnit.SECONDS));
}
#Configuration
#EnableKafka
public class Config {
#Bean
ConcurrentKafkaListenerContainerFactory<Integer, String>
kafkaListenerContainerFactory() {
ConcurrentKafkaListenerContainerFactory<Integer, String> factory =
new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(consumerFactory());
return factory;
}
#Bean
public ConsumerFactory<Integer, String> consumerFactory() {
return new DefaultKafkaConsumerFactory<>(consumerConfigs());
}
#Bean
public Map<String, Object> consumerConfigs() {
Map<String, Object> props = new HashMap<>();
// props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, embeddedKafka.getBrokersAsString());
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
return props;
}
#Bean
public ProducerFactory<Integer, String> producerFactory() {
return new DefaultKafkaProducerFactory<>(producerConfigs());
}
#Bean
public Map<String, Object> producerConfigs() {
Map<String, Object> props = new HashMap<>();
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, IntegerSerializer.class);
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, IntegerSerializer.class);
// props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, embeddedKafka.getBrokersAsString());
props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
return props;
}
#Bean
public KafkaTemplate<Integer, String> kafkaTemplate() {
return new KafkaTemplate<Integer, String>(producerFactory());
}
}
}
But when I change that template.send("annotated1", "key-foo", "foo"); it will work. I have used
#Bean
public Map<String, Object> producerConfigs() {
Map<String, Object> props = new HashMap<>();
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, IntegerSerializer.class);
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, IntegerSerializer.class);
props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
return props;
}
this configuration as well. But it is still giving me the
Caused by: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
If someone there please help me. thanks

Answer 1

You need to add the main application class and Config class to the #SpringBootTest
#SpringBootTest(classes = { So61985794Application.class, So61985794ApplicationTests.Config.class })
to override Boot's normal configuration.