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Strange Java error in service framework

  • 7 October 2021
  • 2 replies
  • 21 views

I’m trying to debug this code in a service framework class;

consumer = new org.apache.kafka.clients.consumer.KafkaConsumer(props);
consumer.subscribe(java.util.Collections.singletonList(topicName));
try {
while (true) {
org.apache.kafka.clients.consumer.ConsumerRecords records = consumer.poll(100L);
for (org.apache.kafka.clients.consumer.ConsumerRecord record : records) {
// Some more code here
}
}
} finally {
consumer.close();
}

Compilation of this code gives this ‘helpful’ error:

[source error] ; is missing

 

The (almost exact) same code in Eclipse works fine:

KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);
consumer.subscribe(Arrays.asList(topicName));
try {
while (true) {
ConsumerRecords<String, String> records = consumer.poll(100L);
for (ConsumerRecord<String, String> record : records) {
System.out.printf("offset = %d, key = %s, value = %s\n", record.offset(), record.key(), record.value());
}
}
} finally {
consumer.close();
}

The error is triggered by this line:

for (org.apache.kafka.clients.consumer.ConsumerRecord record : records)

Anyone have any idea what the problem might be? Or have some tips on how to pinpoint the issue?

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Best answer by Gert.K 7 October 2021, 15:56

View original

2 replies

Thanks for the pointer, @Gert.K ! I did have to explicitly cast the result of the iterator to an org.apache.kafka.clients.consumer.ConsumerRecord, but apart from that your sample code worked perfectly!

java.util.Iterator recordIterator = consumer.poll(100L).iterator();
while (recordIterator.hasNext()) {
org.apache.kafka.clients.consumer.ConsumerRecord record = (org.apache.kafka.clients.consumer.ConsumerRecord)recordIterator.next();
log.debug("Event received: " + record.offset() + " " + record.key() + " " + record.value());
}

 

Hey Marc,

Your code is perfectly fine, but it’s the service definer that’s not cooperating. This issue is that you’re using a foreach construction that the service definer can’t handle at the moment. I can reproduce it with a simple string array

String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
for (String car : cars) {
System.out.println(car);
}

I looked at the kafka documentation and saw that the ConsumerRecords has an iterator. Can you try to use it like that for now?

org.apache.kafka.clients.consumer.ConsumerRecords<String, String> records = consumer.poll(100L);
java.util.Iterator recordIterator = records.iterator();
while(recordIterator.hasNext()){
org.apache.kafka.clients.consumer.ConsumerRecord<String, String> r = recordIterator.next();
// Do stuff with r
}

Kind regards,

Gert

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