依然是基于《kafka在windows上的安装、运行》一文搭建的环境进行Java的调用开发。
实例一：
生产者代码ProducerDemo.java：
package com.bijian.study;
import java.util.Properties;
import org.apache.kafka.clients.producer.Callback;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;
public class ProducerDemo {
public static void main(String[] args) {
String topic = "test";
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092"); //这里的localhost可以改成机器名或ip
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("acks", "all");
props.put("retries", 1);
Producer<String, String> producer = new KafkaProducer<String, String>(props);
producer.send(new ProducerRecord<String, String>(topic, "bijian"), new Callback() {
@Override
public void onCompletion(RecordMetadata metadata, Exception e) {
if (e != null) {
e.printStackTrace();
} else {
System.out.println(metadata.toString());//org.apache.kafka.clients.producer.RecordMetadata@1d89e2b5
System.out.println(metadata.offset());//1
}
}
});
producer.send(new ProducerRecord<String, String>(topic, "ni hao"), new Callback() {
@Override
public void onCompletion(RecordMetadata metadata, Exception e) {
if (e != null) {
e.printStackTrace();
} else {
System.out.println(metadata.toString());//org.apache.kafka.clients.producer.RecordMetadata@1d89e2b5
System.out.println(metadata.offset());//1
}
}
});
producer.flush();
producer.close();
}
}消费者代码ConsumerDemo.java：
package com.bijian.study;
import java.util.Arrays;
import java.util.Properties;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
public class ConsumerDemo {
public static void main(String[] args) {
String topic = "test";
Properties props = new Properties();
props.put("bootstrap.servers", "10.36.33.210:9092"); //这里的localhost可以改成机器名或ip
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.setProperty("group.id", "0");
props.setProperty("enable.auto.commit", "true");
props.setProperty("auto.offset.reset", "latest");
KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);
consumer.subscribe(Arrays.asList(topic));
while(true) {
ConsumerRecords<String, String> records = consumer.poll(1000);
//System.out.println(records.count());
for (ConsumerRecord<String, String> record : records) {
System.out.println(record);
// consumer.seekToBeginning(new TopicPartition(record.topic(), record.partition()));
}
}
}
}运行生产者输出如下：
test-0@236
236
test-0@237
237再运行消费者输出如下：
ConsumerRecord(topic = test, partition = 0, offset = 236, CreateTime = 1545754563805, serialized key size = -1, serialized value size = 6, headers = RecordHeaders(headers = [], isReadOnly = false), key = null, value = bijian)
ConsumerRecord(topic = test, partition = 0, offset = 237, CreateTime = 1545754563816, serialized key size = -1, serialized value size = 6, headers = RecordHeaders(headers = [], isReadOnly = false), key = null, value = ni hao) 注意：auto.offset.reset这里设置为earliest，是为了consumer能够从头开始读取内容即offset=0开始，在org.apache.kafka.clients.consumer.ConsumerConfig中对其意义的描述如下：What to do when there is no initial offset in Kafka or if the current offset does not exist any more on the server (e.g. because that data has been deleted): earliest: automatically reset the offset to the earliest offset；latest: automatically reset the offset to the latest offset；none: throw exception to the consumer if no previous offset is found for the consumer's group；anything else: throw exception to the consumer。consumer.seekToBeginning也可以设置offset，但是跟源码发现，This function evaluates lazily, seeking to the final offset in all partitions only when {@link #poll(long)} or {@link #position(TopicPartition)} are called.也就是说seekToBeginning()的设置要生效的话，必须在poll或则position方法调用后设置seekToBeginning()才行。
earliest：当各分区下有已提交的offset时，从提交的offset开始消费；无提交的offset时，从头开始消费
latest：当各分区下有已提交的offset时，从提交的offset开始消费；无提交的offset时，消费新产生的该分区下的数据
none：topic各分区都存在已提交的offset时，从offset后开始消费；只要有一个分区不存在已提交的offset，则抛出异常
实例二：
生产者代码KafkaProducerExample.java：
package com.bijian.test;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;
import java.util.Properties;
public class KafkaProducerExample {
public static void main(String[] args) {
String topic = "test02";
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("acks", "all");
props.put("retries", 0);
props.put("batch.size", 16384);
props.put("linger.ms", 1);
props.put("buffer.memory", 33554432);
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
Producer<String, String> producer = new KafkaProducer<>(props);
for(int i = 0; i < 100; i++)
// producer.send(new ProducerRecord<>("test", Integer.toString(i), Integer.toString(i)));
producer.send(new ProducerRecord<String, String>(topic, "Hello"));
producer.close();
}
}消费者代码KafkaConsumerExample.java：
package com.bijian.test;
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;
public class KafkaConsumerExample {
public static void main(String[] args) {
String topic = "test02";
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("group.id", "test");
props.put("enable.auto.commit", "true");
props.put("auto.commit.interval.ms", "1000");
props.put("session.timeout.ms", "30000");
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<>(props);
consumer.subscribe(Arrays.asList(topic));
while (true) {
ConsumerRecords<String, String> records = consumer.poll(100);
for (ConsumerRecord<String, String> record : records)
System.out.printf("offset = %d, key = %s, value = %s\n", record.offset(), record.key(), record.value());
}
}
}先运行生产者后，再运行消费者，消费者运行结果如下（共输出100个消息）：
offset = 100, key = null, value = Hello
offset = 101, key = null, value = Hello
offset = 102, key = null, value = Hello
offset = 103, key = null, value = Hello
...
offset = 196, key = null, value = Hello
offset = 197, key = null, value = Hello
offset = 198, key = null, value = Hello
offset = 199, key = null, value = Hello本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
