Kafka实战二

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前言

在上一章 Kafka实战 中我们在局域网中搭建了一个Kafka节点，并尝试了通过命令行脚本来实现本地消息的发布与接收，了解了主从节点之间的关系等。这一章主要实现在本机通过Java代码实现对局域网中的Kafka节点进行消息的发布与接收。

准备工作

在Java中进行Kafka编程需要依赖kafka和kafka-clients两个包，下面直接提供maven配置文件pom.xml，不要忘记修改工程名:

<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>Test</groupId>    <artifactId>Test</artifactId>    <version>0.0.1-SNAPSHOT</version>    <build>        <sourceDirectory>src</sourceDirectory>        <plugins>            <plugin>                <artifactId>maven-compiler-plugin</artifactId>                <version>3.3</version>                <configuration>                    <source>1.7</source>                    <target>1.7</target>                </configuration>            </plugin>        </plugins>    </build>    <dependencies>        <dependency>            <groupId>org.apache.kafka</groupId>            <artifactId>kafka-clients</artifactId>            <version>0.9.0.0</version>        </dependency>        <dependency>            <groupId>org.apache.kafka</groupId>            <artifactId>kafka_2.10</artifactId>            <version>0.9.0.0</version>        </dependency>    </dependencies></project>

生产者

生产者有两种发布方式，同步和异步。异步方式增加了一个Callback参数来实现在消息成功发送后，开展后续的工作。

import java.util.Properties;import java.util.concurrent.ExecutionException;import org.apache.kafka.clients.producer.Callback;import org.apache.kafka.clients.producer.KafkaProducer;import org.apache.kafka.clients.producer.ProducerRecord;import org.apache.kafka.clients.producer.RecordMetadata;public class Producer extends Thread{  private final KafkaProducer<Integer, String> producer;  private final String topic;  // 是否需要异步发送  private final Boolean isAsync;  // 装有Kafka的机器的IP地址  private final String serverIp = "10.64.***.***";  public Producer(String topic, Boolean isAsync)  {    Properties props = new Properties();    props.put("bootstrap.servers", serverIp+":9092");    props.put("client.id", "DemoProducer");    props.put("key.serializer", "org.apache.kafka.common.serialization.IntegerSerializer");    props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");    producer = new KafkaProducer<Integer, String>(props);    this.topic = topic;    this.isAsync = isAsync;  }  public void run() {    int messageNo = 1;    while(true)    {      String messageStr = "Message_" + messageNo;      long startTime = System.currentTimeMillis();      if (isAsync) {        producer.send(new ProducerRecord<Integer, String>(topic,            messageNo,            messageStr), new DemoCallBack(startTime, messageNo, messageStr));      } else {        try {          producer.send(new ProducerRecord<Integer, String>(topic,              messageNo,              messageStr)).get();          System.out.println("Sent message: (" + messageNo + ", " + messageStr + ")");        } catch (InterruptedException e) {          e.printStackTrace();        } catch (ExecutionException e) {          e.printStackTrace();        }      }      ++messageNo;    }  }}class DemoCallBack implements Callback {  private long startTime;  private int key;  private String message;  public DemoCallBack(long startTime, int key, String message) {    this.startTime = startTime;    this.key = key;    this.message = message;  }  /**   * 当异步发送完成后需要进行的处理   **/  public void onCompletion(RecordMetadata metadata, Exception exception) {    long elapsedTime = System.currentTimeMillis() - startTime;    if (metadata != null) {      System.out.println(          "message(" + key + ", " + message + ") sent to partition(" + metadata.partition() +              "), " +              "offset(" + metadata.offset() + ") in " + elapsedTime + " ms");    } else {      exception.printStackTrace();    }  }}

调用方式：

    // 开启生产者线程后，会向Kafka节点中对应的topic发送Message_**类型的消息    boolean isAsync = true;    Producer producerThread = new Producer(KafkaProperties.topic, isAsync);    producerThread.start();

消费者

消费者用来接收特定话题的消息。

import java.util.Collections;import java.util.Properties;import org.apache.kafka.clients.consumer.ConsumerConfig;import org.apache.kafka.clients.consumer.ConsumerRecord;import org.apache.kafka.clients.consumer.ConsumerRecords;import org.apache.kafka.clients.consumer.KafkaConsumer;import kafka.utils.ShutdownableThread;public class Consumer extends ShutdownableThread{  private final KafkaConsumer<Integer, String> consumer;  private final String topic;  private final String serverIp = "10.64.***.***";  public Consumer(String topic)  {    super("KafkaConsumerExample", false);    Properties props = new Properties();    props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, serverIp+":9092");    props.put(ConsumerConfig.GROUP_ID_CONFIG, "DemoConsumer");    props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "true");    props.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, "1000");    props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, "30000");    props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.IntegerDeserializer");    props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");    consumer = new KafkaConsumer<>(props);    this.topic = topic;  }  @Override  public void doWork() {    consumer.subscribe(Collections.singletonList(this.topic));    ConsumerRecords<Integer, String> records = consumer.poll(1000);    for (ConsumerRecord<Integer, String> record : records) {      System.out.println("Received message: (" + record.key() + ", " + record.value() + ") at offset " + record.offset());    }  }  @Override  public String name() {    return null;  }  @Override  public boolean isInterruptible() {    return false;  }}

调用方式：

    //开启消费者线程后，会接收到之前生产者发送的消息    Consumer consumerThread = new Consumer(KafkaProperties.topic);    consumerThread.start();

总结

通过上面的简单的例子，我们就可以在自己的工程中向Kafka发送消息，并接收到自己订阅的消息了。