Kafka 消费者 Demo
import org.apache.kafka.clients.consumer.ConsumerRecord; import org.apache.kafka.clients.consumer.ConsumerRecords; import org.apache.kafka.clients.consumer.KafkaConsumer; import java.util.Arrays; import java.util.Properties; /** * 主要参数: * 1.bootstrap.servers,group.id,key.deserializer,value.deserializer * 2.session.timeout.ms coordinator检测失败的时间,设置为比较小的值 * 3. max.poll.interval.ms consumer处理逻辑最大时间 * 4. auto.offset.reset [earliest,lastest,none] * 5. enable.auto.commit 是否自动提交位移,设置为false,由用户自行提交位移 * 6. fetch.max.bytes 指定consumer单次获取数据的最大字节数 * 7. max.poll.records 单次调用poll的最大返回消息数,默认500 * 8. heartbeat.interval.ms 越小越好 * 9. connections.max.idle.ms Kafka定期关闭空闲Socket的时间 */ public class KafkaConsumerDemo { public static void main(String[] args) { String topic = "test-topic"; String groupId = "test-group"; Properties properties = new Properties(); properties.put("bootstrap.servers","localhost:9092,localhost:9093,localhost:9094"); //必须指定有业务意义的名字 properties.put("group.id",groupId); properties.put("enable.auto.commit","true"); properties.put("auto.commit.interval.ms","1000"); //从最早的消息开始读取 properties.put("auto.offset.reset","earliest"); properties.put("key.deserializer","org.apache.kafka.common.serialization.StringDeserializer"); properties.put("value.deserializer","org.apache.kafka.common.serialization.StringDeserializer"); KafkaConsumer<String,String> consumer = new KafkaConsumer<String, String>(properties); //订阅主题,可以订阅多个主题,还可以使用正则表达式订阅主题 //注意:多次订阅,会覆盖前面的 consumer.subscribe(Arrays.asList(topic)); try{ while(true){ //1000是超时设定,如果有定时要求,可设置,否则建议设置个比较大的值 //通常consumer拿到足够多的数据,会立即返回,否则会阻塞 //poll返回则认为是成功消费了消息,如果发现消费慢需要分析是poll慢还是本身业务逻辑处理慢 ConsumerRecords<String,String> records = consumer.poll(1000); 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(); } } }