我是 Kafka 的新手。我开始在 Kafka 上做我面临以下问题请帮助我解决这个问题提前谢谢。 首先,我正在编写生产者 API,它工作正常,但在执行消费者 API 消息时不显示。
我的代码是这样的:
import java.util.Arrays;
import java.util.Properties;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.ConsumerRecord;
public class ConsumerGroup {
public static void main(String[] args) throws Exception {
String topic = "Hello-Kafka";
String group = "myGroup";
Properties props = new Properties();
props.put("bootstrap.servers", "XXX.XX.XX.XX:9092");
props.put("group.id", group);
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);
try {
consumer.subscribe(Arrays.asList(topic));
System.out.println("Subscribed to topic " + topic);
ConsumerRecords<String, String> records = consumer.poll(100);
System.out.println("records ::" + records);
System.out.println(records.toString());
for (ConsumerRecord<String, String> record : records) {
System.out.println("Record::" + record.offset());
System.out.println(record.key());
System.out.println(record.value());
}
consumer.commitSync();
} catch (Exception e) {
e.printStackTrace();
} finally {
consumer.commitSync();
consumer.close();
}
}
}
回应::
订阅主题 Hello-Kafka 记录::org.apache.kafka.clients.consumer.ConsumerRecords@76b0bfab org.apache.kafka.clients.consumer.ConsumerRecords@76b0bfab
这里不打印 Offset,key,value 控件不会为(ConsumerRecord 记录:记录){ for loop it self 请帮助我。
您正在尝试打印空记录,因此只有 records.toString() 在您的代码中打印,这实际上是类的名称。
我对您的代码进行了一些更改并使其正常运行。看看这是否有帮助。
public class ConsumerGroup {
public static void main(String[] args) throws Exception {
String topic = "Hello-Kafka";
String group = "myGroup";
Properties props = new Properties();
props.put("bootstrap.servers", "xx.xx.xx.xx:9092");
props.put("group.id", group);
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);
try {
consumer.subscribe(Arrays.asList(topic));
System.out.println("Subscribed to topic " + topic);
while(true){
ConsumerRecords<String, String> records = consumer.poll(1000);
if(records.isEmpty()){
}
else{
System.out.println("records ::" + records);
System.out.println(records.toString());
for (ConsumerRecord<String, String> record : records) {
System.out.println("Record::" + record.offset());
System.out.println(record.key());
System.out.println(record.value());
}
consumer.commitSync();
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
consumer.commitSync();
consumer.close();
}
}
}