Spring-Integration-Kafka outbound-channel-adapter Send message

Question

Using Spring-Integration-Kafka, With outbound-channel-adapter I am trying to send messages to a topic with name " test "

Through command line terminal, I started zookeeper, kafka and created topic with name "test"

Spring XML configuration

<int:publish-subscribe-channel id="inputToKafka" />

<int-kafka:outbound-channel-adapter id="kafkaOutboundChannelAdapter"
                                    auto-startup="false"
                                    channel="inputToKafka"
                                    kafka-template="template"
                                    sync="true"
                                    topic="test">
</int-kafka:outbound-channel-adapter>

<bean id="template" class="org.springframework.kafka.core.KafkaTemplate">
    <constructor-arg>
        <bean class="org.springframework.kafka.core.DefaultKafkaProducerFactory">
            <constructor-arg>
                <map>
                    <entry key="bootstrap.servers" value="localhost:9092" />
                </map>
            </constructor-arg>
        </bean>
    </constructor-arg>
</bean>

JUnit Test Code

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {
        "classpath:kafka-outbound-context.xml"
        })
public class ProducerTest{

    @Autowired
    @Qualifier("inputToKafka")
    MessageChannel channel;

    @Test
    public void test_send_message() {

        channel.send(MessageBuilder.withPayload("Test Message")
                .setHeader(KafkaHeaders.TOPIC, "test").build());

    }

}

The test case succeeds and on debug i find channel.send() returns true

I inspect the topic through command line with below command, but I don't see any message in the test topic.

bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic test --from-beginning

Can somebody why I don't see any messages on my test topic ?

Answer 1

Have you looked in the logs? You need to configure key and value serializers, otherwise you'll get

Caused by: org.apache.kafka.common.config.ConfigException: Missing required configuration "key.serializer" which has no default value.

When using java:

    props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
    props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);

The map keys are key.serializer and value.serializer .