用java（idea）来测试kafka中的生产者和消费者

一、检查环境
先把linux中的zookeeper和kafka都安装，并且启动完成。

二、idea环境
打开idea并且创建maven项目。（不会的自己去百度）
pow.xml：

<dependencies>
    <dependency>
        <groupId>org.apache.kafka</groupId>
        <artifactId>kafka_2.12</artifactId>
        <version>1.0.0</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>org.apache.kafka</groupId>
        <artifactId>kafka-clients</artifactId>
        <version>1.0.0</version>
    </dependency>

    <dependency>
        <groupId>org.apache.kafka</groupId>
        <artifactId>kafka-streams</artifactId>
        <version>1.0.0</version>
    </dependency>
</dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.2</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

生产者：

import org.apache.kafka.clients.producer.*;
import org.apache.kafka.common.serialization.StringSerializer;
import java.util.Properties;
/**
 * @ClassName: ProducerDemo
 * @author: zhl
 * @date: 2019/11/20  9:33
 */
public class ProducerDemo  {  public static void main(String[] args) {
            String topicName = "HelloWorld";//这个是创建好的topic

            // create instance for properties to access producer configs
            Properties props = new Properties();

            //这里是填你linux的ip地址:kafka的端口号
            props.put("bootstrap.servers", "192.168.137.128:9092");

            //Set acknowledgements for producer requests.
            props.put("acks", "all");

            //If the request fails, the producer can automatically retry,
            props.put("retries", 0);

            //Specify buffer size in config
            props.put("batch.size", 16384);

            //Reduce the no of requests less than 0
            props.put("linger.ms", 1);

            //The buffer.memory controls the total amount of memory available to the producer for buffering.
            props.put("buffer.memory", 33554432);

            props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
            props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
            Producer<String, String> producer = new KafkaProducer<String, String>(props);

            for (int i = 0; i < 10; i++)
                producer.send(new ProducerRecord<String, String>(topicName, Integer.toString(i), Integer.toString(i)));
            System.out.println("Message sent successfully");
            producer.close();
        }
}

消费者：

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.common.serialization.StringDeserializer;
import java.util.Arrays;
import java.util.Properties;

/**
 * @ClassName: ConsumerDemo
 * @author: zhl
 * @date: 2019/11/20  9:33
 */
public class ConsumerDemo {
public static void main(String[] args) throws Exception
{

    //Kafka consumer configuration settings
    String topicName = "HelloWorld";//创建好的topic
    Properties props = new Properties();

    props.put("bootstrap.servers", "192.168.137.128:9092");//地址和端口号
    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", StringDeserializer.class.getName());
    props.put("value.deserializer", StringDeserializer.class.getName());
    KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);

    //Kafka Consumer subscribes list of topics here.
    consumer.subscribe(Arrays.asList(topicName));

    //print the topic name
    System.out.println("Subscribed to topic " + topicName);
    int i = 0;

    while (true)
    {
        ConsumerRecords<String, String> records = consumer.poll(100);
        for (ConsumerRecord<String, String> record : records)

            // print the offset,key and value for the consumer records.
            System.out.printf("offset = %d, key = %s, value = %s\n", record.offset(), record.key(), record.value());
    }
}
}

备注：
1，如果，不会创建topic的话，看这篇文章，这里面包括topic的查看，销毁，创建，打开生产者和消费者的命令都有kafka命令大全
2，先执行ConsumerDemo（消费者），再执行ProducerDemo（生产者）。因为执行好了消费者之后，你才能去生产，执行了之后，消费者就相当于再等待生产。执行了之后的界面如下：
生产者页面：

消费者页面：

此时打开linux里面的消费者，然后再执行生产者的代码，也能看到消费：

注：如果执行了消费者，再执行生产者之后，发现消费者没数据：接着你就来看这篇文章：测试生产者和消费者代码，发现消费者并没有输出数据，怎么办？（Kafka服务器允许客户端远程连接）