Can't get KafkaEmbedded's port when application context loads about spring-kafka

[garyrussell]

Here's one solution...

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package org.springframework.kafka.core;

import static org.assertj.core.api.Assertions.assertThat;

import java.util.HashMap;
import java.util.Map;

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.junit.ClassRule;
import org.junit.Test;
import org.junit.runner.RunWith;

import org.springframework.beans.DirectFieldAccessor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
import org.springframework.core.Ordered;
import org.springframework.kafka.test.rule.KafkaEmbedded;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.TestContext;
import org.springframework.test.context.TestExecutionListeners;
import org.springframework.test.context.TestExecutionListeners.MergeMode;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.support.AbstractTestExecutionListener;

/**
 * @author Gary Russell
 * @since 1.0
 *
 */
@ContextConfiguration
@RunWith(SpringJUnit4ClassRunner.class)
@TestExecutionListeners(mergeMode = MergeMode.MERGE_WITH_DEFAULTS,
    listeners = SpringWithEmbeddedTests.KafkaEmbeddedTestExecutionListener.class)
public class SpringWithEmbeddedTests {

    private static final String KAFKA_BROKER_ADDRESSES = "kafka.broker.addresses";

    @ClassRule
    public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true, "foo");

    @Autowired
    private ConsumerFactory<?, ?> consumerFactory;

    @Test
    public void test() {
        DirectFieldAccessor accessor = new DirectFieldAccessor(this.consumerFactory);
        @SuppressWarnings("unchecked")
        Map<String, Object> configs = (Map<String, Object>) accessor.getPropertyValue("configs");
        assertThat(configs.get("bootstrap.servers")).isEqualTo(embeddedKafka.getBrokersAsString());
    }

    public static class KafkaEmbeddedTestExecutionListener extends AbstractTestExecutionListener {

        @Override
        public void beforeTestClass(TestContext testContext) throws Exception {
            System.setProperty(KAFKA_BROKER_ADDRESSES, embeddedKafka.getBrokersAsString());
        }

        @Override
        public int getOrder() {
            return Ordered.HIGHEST_PRECEDENCE;
        }


    }

    @Configuration
    public static class Config {

        @Value("${" + KAFKA_BROKER_ADDRESSES + "}")
        private String brokers;

        @Bean
        public static PropertySourcesPlaceholderConfigurer configurer() {
            return new PropertySourcesPlaceholderConfigurer();
        }

        @Bean
        public ConsumerFactory<String, String> consumerFactory() {
            Map<String, Object> props = new HashMap<>();
            props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, brokers);
            // ...
            return new DefaultKafkaConsumerFactory<>(props);
        }

    }

}

[garyrussell]

Using a fixed port is probably ok locally but could be a problem on a CI build server.

[artembilan]

M-m-m. The sample from existing test-case:

@ClassRule
public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true, ...);
...
@Bean
public Map<String, Object> consumerConfigs() {
    Map<String, Object> consumerProps = KafkaTestUtils.consumerProps("testAnnot", "true", embeddedKafka);
    consumerProps.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
    return consumerProps;
}

where KafkaTestUtils.consumerProps() does exactly what you ask:

return consumerProps(embeddedKafka.getBrokersAsString(), group, autoCommit);
...
Map<String, Object> props = new HashMap<>();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, brokers);

[garyrussell]

@artembilan I believe the use case is for testing a production @Configuration class that is not embedded within the test case - i.e. doesn't (and must not) have visibility to the embeddedKafka static field.

[artembilan]

Oh! Sorry, my fault do not read the question.

Interesting, this works for me well:

@ClassRule
public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true, ...);

@BeforeClass
public static void setup() {
    System.setProperty("kafka.brokers", embeddedKafka.getBrokersAsString());
}
...
@Configuraiton
....
    @Value("${kafka.brokers}")
    private String brokers;

[YoannBuch]

Thank you Gary!! Pretty cool trick :)

[garyrussell]

@artembilan 's solution is certainly simpler 😄