spring Kafka integration test listener not working

Question

I'm trying integration testing using spring-boot and spring embedded Kafka. I'm able to produce message to spring embedded Kafka server but instead of test listener the listener in service class is trying to consume the records and

KafkaProducerConfigTest Config class with all beans

@EnableKafka
@TestConfiguration
public class KafkaProducerConfigTest {

@Bean
public EmbeddedKafkaBroker embeddedKafkaBroker() {
    return new EmbeddedKafkaBroker(1,false,2,"test-events");
}

@Bean
public ProducerFactory<String, Object> producerFactory() {
    Map<String, Object> props = new HashMap<>();
    props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, embeddedKafkaBroker().getBrokersAsString());
    props.put(ProducerConfig.RETRIES_CONFIG, 0);
    props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
    props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, JsonSerializer.class);
    return new DefaultKafkaProducerFactory<>(props);
}

@Bean
public KafkaTemplate<String, Object> kafkaTemplate() {
    KafkaTemplate<String, Object> kafkaTemplate = new KafkaTemplate<>(producerFactory());
    return kafkaTemplate;
   }

@Bean("consumerFactory")
 public ConsumerFactory<String, Object> createConsumerFactory() {
     Map<String, Object> props = new HashMap<>();
     props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, embeddedKafkaBroker().getBrokersAsString());
     props.put(ConsumerConfig.GROUP_ID_CONFIG, "group1");
     props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, true);
     return new DefaultKafkaConsumerFactory<>(props, new StringDeserializer(), new JsonDeserializer<>(Object.class,false));
 }

@Bean("kafkaListenerContainerFactory")
 public ConcurrentKafkaListenerContainerFactory<String, Object> kafkaListenerContainerFactory() {
     ConcurrentKafkaListenerContainerFactory<String, Object> factory = new ConcurrentKafkaListenerContainerFactory<>();
     factory.setConsumerFactory(createConsumerFactory());
     factory.setBatchListener(true);
     factory.setMessageConverter(new BatchMessagingMessageConverter(converter()));
     factory.getContainerProperties().setAckMode(AckMode.BATCH);
     return factory;
 }

@Bean
public StringJsonMessageConverter converter() {
    return new StringJsonMessageConverter();
}

@Bean
public Listener listener() {
    return new Listener();
}

public class Listener {
    public final CountDownLatch latch = new CountDownLatch(1);

    @Getter
    public List<Professor> list;

    @KafkaListener(topics = "test-events", containerFactory = "kafkaListenerContainerFactory")
    public void listen1(List<Professor> foo) {

        list=foo;
        this.latch.countDown();
      }
   }

 }

KafkaProducerServiceTest Service test class, but here listener is not consuming any data and I know this test will fail because this is not correct way to do that

@EnableKafka
@SpringBootTest(classes = { KafkaProducerConfigTest.class })
@RunWith(SpringRunner.class)
public class KafkaProducerServiceTest {

@Autowired
private KafkaConsumerService kafkaConsumerService;

@Autowired
private Listener listener;

@Test
public void testReceive() throws Exception {
    kafkaConsumerService.professor(Arrays.asList(new Professor("Ajay", new Department("social", 1234))));
    System.out.println("The professor object is sent to kafka -----------------------------------");
    listener.latch.await();
    System.out.println(listener.getList());

    }

}

Error

2019-02-19 15:18:32.620 ERROR 22387 --- [ntainer#1-0-C-1] o.s.k.listener.BatchLoggingErrorHandler  : Error while processing:
ConsumerRecord(topic = test-events, partition = 1, offset = 0, CreateTime = 1550611112583, serialized key size = 9, serialized value size = 64, headers = RecordHeaders(headers = [], isReadOnly = false), key = professor, value = {name=Ajay, department={deptName=social, deptId=1234}})

 java.lang.IllegalStateException: Only String or byte[] supported
at org.springframework.kafka.support.converter.StringJsonMessageConverter.extractAndConvertValue(StringJsonMessageConverter.java:140) ~[spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.support.converter.MessagingMessageConverter.toMessage(MessagingMessageConverter.java:134) ~[spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.support.converter.BatchMessagingMessageConverter.convert(BatchMessagingMessageConverter.java:217) ~[spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.support.converter.BatchMessagingMessageConverter.toMessage(BatchMessagingMessageConverter.java:165) ~[spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.listener.adapter.BatchMessagingMessageListenerAdapter.toMessagingMessage(BatchMessagingMessageListenerAdapter.java:174) ~[spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.listener.adapter.BatchMessagingMessageListenerAdapter.onMessage(BatchMessagingMessageListenerAdapter.java:129) ~[spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.listener.adapter.BatchMessagingMessageListenerAdapter.onMessage(BatchMessagingMessageListenerAdapter.java:59) ~[spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.doInvokeBatchListener(KafkaMessageListenerContainer.java:984) [spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.invokeBatchListener(KafkaMessageListenerContainer.java:917) [spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.invokeListener(KafkaMessageListenerContainer.java:900) [spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.run(KafkaMessageListenerContainer.java:753) [spring-kafka-2.2.0.RELEASE.jar:2.2.0.RELEASE]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_191]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_191]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_191]

Updated based on @Gray Russel sir answer but I still have an issue

Answer 1

Use StringDeserializer and a StringJsonMessageConverter in the container factory (or BytesDeserializer and BytesJsonMessageConverter ); the framework can then determine the target type from the method signature and pass it into the converter.

The deserializer is too far down the stack to do that inference.

Answer 2

It might be late to respond on this discussion. As @Gary Russell mentioned in his reply just use StringDeserializer to deserialize the object.

application.yml to configure Kafka:

server:
 port: 8080
 servlet:
   contextPath: /poi
spring:
   kafka:
consumer:
  bootstrap-servers: localhost:9092
  group-id: rsvp-consumers
  auto-offset-reset: earliest
  key-deserializer: org.apache.kafka.common.serialization.StringDeserializer
  value-deserializer: org.apache.kafka.common.serialization.StringDeserializer
  properties:
    spring:
      json:
        type:
          mapping: poi:org.ajeet.learnings.spring.springboot.model.POI
producer:
  bootstrap-servers: localhost:9092
  key-serializer: org.apache.kafka.common.serialization.StringSerializer
  value-serializer: org.springframework.kafka.support.serializer.JsonSerializer
  properties:
    spring:
      json:
        type:
          mapping: poi:org.ajeet.learnings.spring.springboot.model.POI
topics: spatial

Kafka event class:

public final class POI {
private final double longitude;
private final double latitude;
private final POI_Type type;
private final String description;

@JsonCreator
public POI(@JsonProperty("longitude") double longitude,
           @JsonProperty("latitude") double latitude,
           @JsonProperty("type") POI_Type type,
           @JsonProperty("description") String description) {
    this.longitude = longitude;
    this.latitude = latitude;
    this.type = type;
    this.description = description;
}
public double getLongitude() {
    return longitude;
}
public double getLatitude() {
    return latitude;
}
public String getDescription() {
    return description;
}}

In your application class register StringJsonMessageConverter (you can create this bean somewhere else too), this is converting string to required object that is POI in this :

@SpringBootApplication
@ComponentScan("org.ajeet.learnings.spring")
public class SpringBootKafkaApplication {

public static void main(String[] args) {
    SpringApplication.run(SpringBootKafkaApplication.class, args);
}
/**
 * We are using a StringDeserializer in kafka consumer properties
 *  And this converter is converting the message from string to required type.
 *
 * @return RecordMessageConverter
 */
@Bean
public RecordMessageConverter converter() {
    return new StringJsonMessageConverter();
}}

This is consumer:

@Service
public final class POIEventConsumer {
private final Logger LOG = LoggerFactory.getLogger(POIEventConsumer.class);

/**
 * Read topic names from application.yaml
 *
 * @param pointOfInterest
 * @throws IOException
 */
@KafkaListener(topics = "#{'${spring.kafka.topics}'.split(',')}")
public void consume(POI pointOfInterest) throws IOException {
    LOG.info(pointOfInterest.toString());
} }

This is producer:

@Service
public class POIEventProducer {
private static final Logger LOG = LoggerFactory.getLogger(POIEventProducer.class);

@Value("${spring.kafka.topics}")
private String topic;

@Autowired
private KafkaTemplate<String, POI> kafkaTemplate;

public void sendMessage(POI pointOfInterest) {
    this.kafkaTemplate.send(topic, pointOfInterest);
}}

You can use a controller to test it:

@RestController
@RequestMapping(value = "/kafka")
public final class POIEventController {
private final Logger LOG = LoggerFactory.getLogger(POIEventController.class);

@Autowired
private POIEventProducer poiEventProducer;


/**
 * Post request url: http://localhost:8080/poi/kafka/publish
 * Example of request body: {"longitude":77.100281, "latitude": 28.556160, "type": "Airport", "description": "Indira Gandhi International Airport New Delhi"}
 *
 * @param pointOfInterest
 */
@RequestMapping(value = "/publish",
        method = RequestMethod.POST,
        consumes = MediaType.APPLICATION_JSON_VALUE)
public void sendMessageToKafkaTopic(@RequestBody POI pointOfInterest) {
    this.poiEventProducer.sendMessage(pointOfInterest);
}}