Using Spring EL to add optional postfix from properties to consumerGroup in #KafkaListener - spring-boot

Question

I have simple spring boot application with Kafka Consumers that looks like
#KafkaListener(topics="topic", groupId="SOME_CONSTANT") {
....
}
What I am required to do Is to add optional spring boot property (from env variables but that is not important) lets say:
myapp.env: TEST
And when that variable is present I should automatically update consumer group to be
SOME_CONSTANT-TEST
I am playing with SPEL
#KafkaListener(topics="topic", groupId="#{ '${myApp.env}' == null ? 'SOME_CONSTANT' : 'SOME_CONSTANT' + '-' + '${myApp.env}}'") {
....
}
But that does not seem to work :/ Any Ideas?

Answer 1

You can use the T operator to read the constant's value, and use the colon ':' for the case when there's no env variable:
#KafkaListener(topics="topic", groupId="#{ '${my.app.env:}' == '' ? T(com.mypackage.MyListener).SOME_CONSTANT : T(com.mypackage.MyListener).SOME_CONSTANT + '-' + '${my.app.env:}'}")
Here's a sample application with this solution:
package org.spring.kafka.playground;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.kafka.core.KafkaOperations;
import org.springframework.kafka.support.KafkaHeaders;
import org.springframework.messaging.handler.annotation.Header;
import org.springframework.stereotype.Component;
#SpringBootApplication
public class SO71291726 {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(SO71291726.class, args);
try {
Thread.sleep(10000);
}
catch (InterruptedException e) {
Thread.interrupted();
throw new RuntimeException("Interrupted");
}
KafkaOperations kafkaTemplate = context.getBean("kafkaTemplate", KafkaOperations.class);
kafkaTemplate.send("topic", "My message");
}
Logger log = LoggerFactory.getLogger(this.getClass());
public static final String SOME_CONSTANT = "my-group-id-constant";
#Component
class MyListener {
#KafkaListener(topics="topic", groupId="#{ '${71291726.my.app.env:}' == '' ? T(org.spring.kafka.playground.SO71291726).SOME_CONSTANT : T(org.spring.kafka.playground.SO71291726).SOME_CONSTANT + '-' + '${71291726.my.app.env:}'}")
void listen(String message, #Header(KafkaHeaders.GROUP_ID) String groupId) {
log.info("Received message {} from group id {} ", message, groupId);
}
}
}
Output:
2022-02-28 14:26:14.733 INFO 18841 --- [ntainer#0-0-C-1] 1291726$$EnhancerBySpringCGLIB$$cf264156 : Received message My message from group id my-group-id-constant
If I add 71291726.my.app.env = TEST to the application.properties file:
2022-02-28 14:34:03.900 INFO 18870 --- [ntainer#0-0-C-1] 1291726$$EnhancerBySpringCGLIB$$e1a5933e : Received message My message from group id my-group-id-constant-TEST