Pass list of topics from application yml to KafkaListener - spring-boot

Question

I have the following application.yml:
service:
kafka:
groupId: 345
consumer:
topics:
-
name: response
producer:
topics:
-
name: request1
num-partitions: 5
replication-factor: 1
-
name: request2
num-partitions: 3
replication-factor: 1
How can I access the list of topic names using spel for passing to KafkaListener annotation?
#KafkaListener(topics = "#{'${service.kafka.consumer.topics.name}'}", containerFactory = "kafkaListenerContainerFactory")
public void receive(String payload, #Header(KafkaHeaders.RECEIVED_TOPIC)String topic) {

Answer 1

Use configuration properties and collection projection...
#ConfigurationProperties("service.kafka.producer")
#Component
public class ConfigProps {
List<Topic> topics = new ArrayList<>();
public List<Topic> getTopics() {
return this.topics;
}
public void setTopics(List<Topic> topics) {
this.topics = topics;
}
#Override
public String toString() {
return "ConfigProps [topics=" + this.topics + "]";
}
public static class Topic {
private String name;
private int numPartitions;
private short replicationFactor;
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public int getNumPartitions() {
return this.numPartitions;
}
public void setNumPartitions(int numPartitions) {
this.numPartitions = numPartitions;
}
public short getReplicationFactor() {
return this.replicationFactor;
}
public void setReplicationFactor(short replicationFactor) {
this.replicationFactor = replicationFactor;
}
#Override
public String toString() {
return "Topic [name=" + this.name + ", numPartitions=" + this.numPartitions + ", replicationFactor="
+ this.replicationFactor + "]";
}
}
}
and
#SpringBootApplication
public class So52741016Application {
public static void main(String[] args) {
SpringApplication.run(So52741016Application.class, args);
}
#KafkaListener(groupId = "${service.kafka.groupId}", topics = "#{configProps.topics.![name]}")
public void listener(String in) {
}
#Bean
public SmartLifecycle createTopics(KafkaAdmin admin, ConfigProps props) {
return new SmartLifecycle() {
#Override
public int getPhase() {
return Integer.MIN_VALUE;
}
#Override
public void stop() {
}
#Override
public void start() {
try (AdminClient client = AdminClient.create(admin.getConfig())) {
CreateTopicsResult createTopics = client.createTopics(props.topics.stream()
.map(t -> new NewTopic(t.getName(), t.getNumPartitions(), t.getReplicationFactor()))
.collect(Collectors.toList()));
createTopics.all().get();
}
catch (Exception e) {
// e.printStackTrace();
}
}
#Override
public boolean isRunning() {
return false;
}
#Override
public void stop(Runnable callback) {
}
#Override
public boolean isAutoStartup() {
return true;
}
};
}
}
and
2018-10-10 11:20:25.813 INFO 14979 --- [ntainer#0-0-C-1] o.s.k.l.KafkaMessageListenerContainer : partitions assigned: [request1-4, request2-0, request1-0, request2-1, request1-1, request2-2, request1-2, request1-3]
Of course, this is only the producer topics, but you can handle them all this way.