我正在尝试使用spring framework for kafka测试kafka生产者代码。我的测试课看起来像这样。

@EmbeddedKafka
public class KafkaProducerTest
{
    @ClassRule
    public static EmbeddedKafkaRule embeddedKafkaRule =
            new EmbeddedKafkaRule(1, true, "KafkaProducerTopic");
    private EmbeddedKafkaBroker embeddedKafkaBroker = embeddedKafkaRule.getEmbeddedKafka();
    private KafkaProducer<String, Long> producer;

    @Before
    public void setup()
    {
        Properties producerProperties = new Properties();
        Map<String, Object> producerConfigs =
            new HashMap<>(KafkaTestUtils.producerProps(embeddedKafkaBroker));
        for (Map.Entry<String, Object> entry : producerConfigs.entrySet()) {
            producerProperties.put(entry.getKey(), entry.getValue());
        }
        producerProperties.put("key.serializer", StringSerializer.class.getName());
        producerProperties.put("value.serializer", LongSerializer.class.getName());

        producer = new KafkaProducer<>(producerProperties);
    }
}

我还没有在producer上编写任何测试用例。但是当我运行上面的测试类时，它会抛出如下警告。

[kafka-producer-network-thread | producer-2] WARN org.apache.kafka.clients.NetworkClient - [Producer clientId=producer-2] Connection to node 0 (localhost/127.0.0.1:36994) could not be established. Broker may not be available.
[kafka-producer-network-thread | producer-5] WARN org.apache.kafka.clients.NetworkClient - [Producer clientId=producer-5] Connection to node 0 (localhost/127.0.0.1:36994) could not be established. Broker may not be available.
[kafka-producer-network-thread | producer-6] WARN org.apache.kafka.clients.NetworkClient - [Producer clientId=producer-6] Connection to node 0 (localhost/127.0.0.1:36994) could not be established. Broker may not be available.
[kafka-producer-network-thread | producer-7] WARN org.apache.kafka.clients.NetworkClient - [Producer clientId=producer-7] Connection to node 0 (localhost/127.0.0.1:36994) could not be established. Broker may not be available.
[kafka-producer-network-thread | producer-8] WARN org.apache.kafka.clients.NetworkClient - [Producer clientId=producer-8] Connection to node 0 (localhost/127.0.0.1:36994) could not be established. Broker may not be available.
[kafka-producer-network-thread | producer-1] WARN org.apache.kafka.clients.NetworkClient - [Producer clientId=producer-1] Connection to node 0 (localhost/127.0.0.1:36994) could not be established. Broker may not be available.

似乎生产者线程无法连接到kafka代理。我是新来测试Kafka与Spring Boot。我看了一些文章，但还是想不出解决这个问题的办法。