Kafka的Java客户端-demo版
0. 订单类
package com.hao.entity;
public class Order {
private Long orderId;
private int count;
public Order(Long orderId, int count) {
this.orderId = orderId;
this.count = count;
}
public Order() {
}
public Long getOrderId() {
return orderId;
}
public void setOrderId(Long orderId) {
this.orderId = orderId;
}
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
}
1. 依赖
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.aho</groupId>
<artifactId>kafka-demo</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.47</version>
</dependency>
<dependency>
<groupId>org.apache.kafka</groupId>
<artifactId>kafka-clients</artifactId>
<version>2.4.1</version>
</dependency>
</dependencies>
</project>
2. 生产者发送消息
2.1 同步发送
package com.hao.kafka;
import com.alibaba.fastjson.JSON;
import com.hao.entity.Order;
import org.apache.kafka.clients.producer.*;
import org.apache.kafka.common.serialization.StringSerializer;
import java.util.Properties;
import java.util.concurrent.ExecutionException;
public class MyProducerDemo01 {
// 1. topic名
private static final String TOPIC_NAME = "my-replicated-topic";
public static void main(String[] args) throws ExecutionException, InterruptedException {
// 2. 配置
Properties properties = new Properties();
// 连接kafkaIP
properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.100.108:9092,192.168.100.108:9093,192.168.100.108:9094");
// 序列化器
properties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
// 设置acks
properties.put(ProducerConfig.ACKS_CONFIG,"0");
// 3. 创建一个要发送的消息对象,并带上配置
Producer<String,String> producer = new KafkaProducer<String, String>(properties);
// 4. 封装消息对象
// 生成order对象
Order order = new Order(1001L,2);
// 封装
ProducerRecord<String,String> producerRecord = new ProducerRecord<String, String>(TOPIC_NAME,
String.valueOf(order.getOrderId()),
JSON.toJSONString(order));
RecordMetadata metadata = producer.send(producerRecord).get();
System.out.println("同步方式发送消息结果:" + "topic-" + metadata.topic() + "|partition-"
+ metadata.partition() + "|offset-" + metadata.offset());
}
}
2.2 异步发送
package com.hao.kafka;
import com.alibaba.fastjson.JSON;
import com.hao.entity.Order;
import org.apache.kafka.clients.producer.*;
import org.apache.kafka.common.serialization.StringSerializer;
import java.util.Properties;
import java.util.concurrent.CountDownLatch;
public class MyProducer02 {
private static final String TOPIC_NAME = "my-replicated-topic";
public static void main(String[] args) throws InterruptedException {
// 1. 创建配置对象
Properties properties = new Properties();
properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.100.108:9092,192.168.100.108:9093,192.168.100.108:9094");
properties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG,StringSerializer.class.getName());
properties.put(ProducerConfig.ACKS_CONFIG,"0");
// 2. 创建一个发送消息的对象,并携带配置对象
Producer<String,String> producer = new KafkaProducer<String, String>(properties);
// 门栓
CountDownLatch countDownLatch = new CountDownLatch(5);
for (int i = 0; i < 5 ; i++) {
// 3. 封装消息对象
// 生成消息---生成订单对象
Order order = new Order((long)i,2);
// 封装
ProducerRecord<String,String> producerRecord = new ProducerRecord<String, String>(TOPIC_NAME,
String.valueOf(order.getOrderId()),
JSON.toJSONString(order));
//异步回调方式发送消息
producer.send(producerRecord, new Callback() {
@Override
public void onCompletion(RecordMetadata recordMetadata, Exception e) {
if (e != null) {
System.err.println("发送消息失败:"+e.getStackTrace());
}
if (recordMetadata != null) {
System.out.println("异步方式发送消息结果:" + "topic-" + recordMetadata.topic() + "|partition-"
+ recordMetadata.partition() + "|offset-" + recordMetadata.offset());
}
countDownLatch.countDown();
}
});
}
// 当countDownLatch变成0之前,一直阻塞
countDownLatch.await();
producer.close();
}
}
3. 消费者消费消息
package com.hao.kafka;
import org.apache.kafka.clients.consumer.*;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.apache.kafka.common.serialization.StringSerializer;
import java.time.Duration;
import java.util.Arrays;
import java.util.Map;
import java.util.Properties;
public class MyConsumer01 {
private static final String TOPIC_NAME = "my-replicated-topic";
private static final String GROUP_NAME = "testGroup999";
public static void main(String[] args) {
// 1. 配置
Properties properties = new Properties();
// kafka集群ip
properties.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.100.108:9092,192.168.100.108:9093,192.168.100.108:9094");
// 序列化器
properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,StringDeserializer.class.getName());
// 消费组的名称
properties.setProperty(ConsumerConfig.GROUP_ID_CONFIG,GROUP_NAME);
/*
// 是否自动提交offset(偏移量),默认是自动提交,true
properties.setProperty(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG,"true");
// 自动提交offset的时间间隔
properties.setProperty(ConsumerConfig.MAX_POLL_INTERVAL_MS_CONFIG,"1000");
*/
/*
当消费主题的是一个新的消费组,或者指定offset的消费方式,offset不存在,那么应该如何消费
latest(默认) :只消费自己启动之后发送到主题的消息
earliest:第一次从头开始消费,以后按照消费offset记录继续消费,这个需要区别于consumer.seekToBeginning(每次都从头开始消费)
*/
properties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
// 是否自动提交offset(偏移量),手动提交,false
properties.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG,"false");
// 一次poll的最大拉去消息的条数,可以根据消费速度来设置
properties.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG,500);
//consumer给broker发送心跳的间隔时间
properties.put(ConsumerConfig.HEARTBEAT_INTERVAL_MS_CONFIG, 1000);
//kafka如果超过10秒没有收到消费者的心跳,则会把消费者踢出消费组,进行rebalance,把分区分配给其他消费者。
properties.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 10 * 1000);
//如果两次poll的时间如果超出了30s的时间间隔,kafka会认为其消费能力过弱,将其踢出消费组。将分区分配给其他消费者。-rebalance
properties.put(ConsumerConfig.MAX_POLL_INTERVAL_MS_CONFIG, 30 * 1000);
// 2. 创建一个要消费的消息对象,并带上配置
KafkaConsumer<String,String> consumer = new KafkaConsumer<String, String>(properties);
// 3. 订阅主题
consumer.subscribe(Arrays.asList(TOPIC_NAME));
// 4. 处理消息
while (true) {
ConsumerRecords<String,String> records = consumer.poll(Duration.ofMillis(1000));
// 具体处理消息
for (ConsumerRecord<String, String> record : records) {
System.out.printf("收到消息:partition = %d,offset = %d, key = %s, value = %s%n", record.partition(),
record.offset(), record.key(), record.value());
}
// 处理完消息后,需要手动提交
if (records.count() > 0) {
// 1. 手动同步提交
// 在kafka返回ack给消费者之前,该方法一直阻塞
// 默认使用手动同步提交,因为在提交之后没有其他逻辑了。
consumer.commitSync();
// 2. 手动异步提交
// consumer.commitAsync(new OffsetCommitCallback() {
// @Override
// public void onComplete(Map<TopicPartition, OffsetAndMetadata> map, Exception e) {
// if (e != null) {
// System.err.println("Commit failed for " + map);
// System.err.println("Commit failed exception: "+e.getStackTrace());
// }
// }
// });
}
}
}
}
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