netty kafka怎样连接

要使用Netty连接Kafka，您需要遵循以下步骤：

1. 添加依赖

首先，您需要在项目中添加Kafka客户端和Netty的依赖。如果您使用的是Maven，可以在pom.xml文件中添加以下依赖：

<dependencies>
    <!-- Kafka客户端 -->
    <dependency>
        <groupId>org.apache.kafka</groupId>
        <artifactId>kafka-clients</artifactId>
        <version>2.8.0</version>
    </dependency>
    <!-- Netty -->
    <dependency>
        <groupId>io.netty</groupId>
        <artifactId>netty-all</artifactId>
        <version>4.1.68.Final</version>
    </dependency>
</dependencies>

2. 创建Kafka生产者

创建一个Kafka生产者，用于将消息发送到Kafka集群。以下是一个简单的示例：

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerRecord;

import java.util.Properties;

public class KafkaProducerExample {
    public static void main(String[] args) {
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

        KafkaProducer<String, String> producer = new KafkaProducer<>(props);
        for (int i = 0; i < 100; i++) {
            producer.send(new ProducerRecord<>("my-topic", Integer.toString(i), Integer.toString(i)));
        }

        producer.close();
    }
}

3. 创建Kafka消费者

创建一个Kafka消费者，用于从Kafka集群接收消息。以下是一个简单的示例：

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;

import java.time.Duration;
import java.util.Collections;
import java.util.Properties;

public class KafkaConsumerExample {
    public static void main(String[] args) {
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("group.id", "test");
        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(Collections.singletonList("my-topic"));

        while (true) {
            ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(100));
            for (ConsumerRecord<String, String> record : records) {
                System.out.printf("offset = %d, key = %s, value = %s%n", record.offset(), record.key(), record.value());
            }
        }
    }
}

4. 使用Netty创建自定义Kafka客户端

要使用Netty创建自定义Kafka客户端，您需要创建一个继承ChannelInboundHandlerAdapter的类，并实现相关的方法。以下是一个简单的示例：

import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.socket.SocketChannel;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerRecord;

public class KafkaClientInitializer extends ChannelInitializer<SocketChannel> {
    private final KafkaProducer<String, String> producer;

    public KafkaClientInitializer(KafkaProducer<String, String> producer) {
        this.producer = producer;
    }

    @Override
    protected void initChannel(SocketChannel ch) {
        ch.pipeline().addLast(new KafkaClientHandler(producer));
    }
}

class KafkaClientHandler extends ChannelInboundHandlerAdapter {
    private final KafkaProducer<String, String> producer;

    public KafkaClientHandler(KafkaProducer<String, String> producer) {
        this.producer = producer;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        // 发送消息到Kafka集群
        for (int i = 0; i < 100; i++) {
            producer.send(new ProducerRecord<>("my-topic", Integer.toString(i), Integer.toString(i)));
        }
        ctx.close();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

5. 启动Netty服务器

创建一个Netty服务器，用于接收客户端连接并处理请求。以下是一个简单的示例：

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class NettyServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) {
                            ch.pipeline().addLast(new StringDecoder());
                            ch.pipeline().addLast(new StringEncoder());
                            ch.pipeline().addLast(new KafkaClientInitializer(createKafkaProducer()));
                        }
                    });

            ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

    private static KafkaProducer<String, String> createKafkaProducer() {
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

        return new KafkaProducer<>(props);
    }
}

现在，您可以运行Netty服务器和Kafka生产者/消费者示例，看到它们如何连接到Kafka集群并发送/接收消息。