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关于netty:Netty网络编程Netty应用与核心模块组件

作者：

jiezi

在

1.用Netty实现群聊零碎

2.用Netty实现心跳检测

3.用Netty编程实现客户端与服务器端的长链接

4.Netty外围模块组件剖析

咱们先通过代码示例，感受一下Netty的应用，而后再分析这些工具类每一个的作用。

1.用Netty实现群聊零碎

咱们用Netty实现一个群聊零碎，实现客户端和服务器端之间的简略通信。

性能点如下：
1）服务器端：能够检测用户上线，离线，并实现音讯转发
2）客户端：通过channel能够把音讯发送给所有其它用户，同时也能接管其它用户发送的信息。

server端：

client端：

server:

package com.example.demo.netty.nettyDemo.chat;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
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;
import lombok.extern.slf4j.Slf4j;

/**
 * @author sulingfeng
 * @title: GroupChatServer
 * @projectName netty-learn
 * @description: TODO
 * @date 2022/7/12 17:12
 */
@Slf4j
public class GroupChatServer {

    private int port;

    public GroupChatServer(int port) {
        this.port = port;
    }

    public void run() throws Exception{
        //两个工作线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try{
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)//应用NioSocketChannel作为通道的实现
                    .option(ChannelOption.SO_BACKLOG, 128)//设置线程队列的连贯数量下限
                    .childOption(ChannelOption.SO_KEEPALIVE, true)//放弃流动连贯状态
                    .childHandler(new ChannelInitializer<SocketChannel>() {

                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {

                            //获取到pipeline
                            ChannelPipeline pipeline = ch.pipeline();
                            //向pipeline退出解码器
                            pipeline.addLast("decoder", new StringDecoder());
                            //向pipeline退出编码器
                            pipeline.addLast("encoder", new StringEncoder());
                            //退出本人的业务解决handler
                            pipeline.addLast(new GroupChatServerHandler());

                        }
                    });
            log.info("netty 服务器启动！");
            ChannelFuture channelFuture = bootstrap.bind(port).sync();
            channelFuture.channel().closeFuture().sync();

        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();

        }

    }

    public static void main(String[] args) throws Exception{
        //启动
        GroupChatServer groupChatServer = new GroupChatServer(10087);
        groupChatServer.run();
    }
}

serverHandler:

package com.example.demo.netty.nettyDemo.chat;

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;
import lombok.extern.slf4j.Slf4j;

import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * @author sulingfeng
 * @title: GroupChatServerHandler
 * @projectName netty-learn
 * @description: TODO
 * @date 2022/7/12 17:21
 */
@Slf4j
public class GroupChatServerHandler extends SimpleChannelInboundHandler<String> {


    private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        channelGroup.writeAndFlush("[客户端]"+channel.remoteAddress()+"退出聊天"+"\n");
        channelGroup.add(channel);
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        channelGroup.writeAndFlush("[客户端]"+channel.remoteAddress()+"来到了\n");

    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        log.info(ctx.channel().remoteAddress()+"上线了~");
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        log.info(ctx.channel().remoteAddress()+"离线了~");
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        Channel channel = ctx.channel();
        //遍历channelGroup，依据不同的状况，回送不同的信息
        channelGroup.forEach(ch->{
            if(channel!=ch){
                ch.writeAndFlush("[客户]：["+channel.remoteAddress()+"]发送了信息："+msg+"\n");
            }else{
                ch.writeAndFlush("[本人]发送了信息："+msg+"\n");
            }
        });
    }

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

}

client:

package com.example.demo.netty.nettyDemo.chat;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import lombok.extern.slf4j.Slf4j;

import java.util.Scanner;


/**
 * @author sulingfeng
 * @title: GroupChatClient
 * @projectName netty-learn
 * @description: TODO
 * @date 2022/7/12 17:33
 */
@Slf4j
public class GroupChatClient {

    //属性
    private final String host;
    private final int port;

    public GroupChatClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public void run() throws Exception{
        EventLoopGroup group = new NioEventLoopGroup();

        try {
            Bootstrap bootstrap = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {

                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {

                            //失去pipeline
                            ChannelPipeline pipeline = ch.pipeline();
                            //退出相干handler
                            pipeline.addLast("decoder", new StringDecoder());
                            pipeline.addLast("encoder", new StringEncoder());
                            //退出自定义的handler
                            pipeline.addLast(new GroupChatClientHandler());
                        }
                    });
            ChannelFuture channelFuture = bootstrap.connect(host, port).sync();
            Channel channel = channelFuture.channel();
            //客户端须要输出信息，创立一个输出循环
            Scanner scanner = new Scanner(System.in);
            while (!scanner.hasNext("#")) {
                String msg = scanner.nextLine();
                //通过channel 发送到服务器端
                channel.writeAndFlush(msg + "\r\n");
            }

        }finally {
            group.shutdownGracefully();
        }



    }

    public static void main(String[] args) throws Exception {
        new GroupChatClient("127.0.0.1", 10087).run();
    }

}

clientHandler:

package com.example.demo.netty.nettyDemo.chat;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import lombok.extern.slf4j.Slf4j;

/**
 * @author sulingfeng
 * @title: GroupChatClientHandler
 * @projectName netty-learn
 * @description: TODO
 * @date 2022/7/12 17:36
 */
@Slf4j
public class GroupChatClientHandler  extends SimpleChannelInboundHandler<String> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String s) throws Exception {
        log.info(s.trim());
    }
}

2.用Netty实现心跳检测

咱们编写一个服务器：
当服务器超过5秒没有读时，就输入读闲暇。
当服务器超过6秒没有写时，就提醒写闲暇。
当服务器超过7秒没有读写时，就提醒读写闲暇。

server:

package com.example.demo.netty.nettyDemo.chat.heartbeat;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
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.logging.LoggingHandler;
import io.netty.handler.timeout.IdleStateHandler;

import java.util.concurrent.TimeUnit;

/**
 * @author sulingfeng
 * @title: BeatServer
 * @projectName netty-learn
 * @description: TODO
 * @date 2022/7/26 13:35
 */
public class BeatServer {

    public static void main(String[] args) throws Exception {
        //两个工作线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap bootstrap = new ServerBootstrap();

            bootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler())
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            /**
                             * IdleStateHandler 是netty提供的解决闲暇状态的处理器
                             * long readerIdleTime 示意长时间没有读，就会发送心跳检测包是否连贯
                             * long writerIdleTime 示意长时间没有写，就会发送心跳检测包是否连贯
                             * long allIdleTime    示意长时间没有读写，就会发送心跳检测包是否连贯
                             */
                            pipeline.addLast(new IdleStateHandler(5,6,7, TimeUnit.SECONDS));

                            pipeline.addLast(new MyHeartHandler());
                        }
                    });
            ChannelFuture channelFuture = bootstrap.bind(10087).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

    }

}

serverHandler:

package com.example.demo.netty.nettyDemo.chat.heartbeat;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.timeout.IdleStateEvent;
import io.netty.handler.timeout.IdleStateHandler;

/**
 * @author sulingfeng
 * @title: MyHeartHandler
 * @projectName netty-learn
 * @description: TODO
 * @date 2022/7/26 13:57
 */
public class MyHeartHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {

        if(evt instanceof IdleStateEvent){
            IdleStateEvent event = (IdleStateEvent)evt;

            String eventType = null;

            switch (event.state()){
                case READER_IDLE:
                    eventType="读闲暇";
                    break;
                case WRITER_IDLE:
                    eventType="写闲暇";
                    break;
                case ALL_IDLE:
                    eventType="读写闲暇";
                    break;
            }

            System.out.println(ctx.channel().remoteAddress()+"--超时工夫--"+eventType);
            System.out.println("服务器做相应解决");
        }

    }
}

3.用Netty编程实现客户端与服务器端的长链接

实现一个基于webSocket的长链接全双工交互，从页面发动调用，客户端就能够和服务端互发信息了。

server:

package com.example.demo.netty.nettyDemo.socket;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
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.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.stream.ChunkedWriteHandler;
import lombok.extern.slf4j.Slf4j;

/**
 * @author sulingfeng
 * @title: MyServer
 * @projectName netty-learn
 * @description: TODO
 * @date 2022/7/13 13:57
 */
@Slf4j
public class MyServer {

    public static void main(String[] args) throws Exception {

        //创立两个线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup(); //8个NioEventLoop

        try{
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap
                    .group(bossGroup,workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {

                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            //因为Http协定，应用http的编码和解码器
                            pipeline.addLast(new HttpServerCodec());
                            //以块的形式写，增加ChunkedWriteHandler处理器
                            pipeline.addLast(new ChunkedWriteHandler());
                            //http数据如果很大，就会将数据分段发送，收回屡次http申请
                            //参数示意byte数组最大长度
                            pipeline.addLast(new HttpObjectAggregator(8192));
                            //浏览器申请的对应接口 ： localhost:7000/hello
                            pipeline.addLast(new WebSocketServerProtocolHandler("/hello"));
                            //自定义的handler ，解决业务逻辑
                            pipeline.addLast(new MyTextWebSocketFrameHandler());
                        }
                    });

            //启动服务器
            ChannelFuture channelFuture = serverBootstrap.bind(7000).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

    }

}

handler:

package com.example.demo.netty.nettyDemo.socket;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;

import java.time.LocalDateTime;

/**
 * @author sulingfeng
 * @title: MyTextWebSocketFrameHandler
 * @projectName netty-learn
 * @description: TODO
 * @date 2022/7/13 14:02
 */
public class MyTextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {


    @Override
    protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
        System.out.println("服务器收到音讯 " + msg.text());
        //回复音讯
        ctx.channel().writeAndFlush(new TextWebSocketFrame("服务器工夫" + LocalDateTime.now() + " " + msg.text()));
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        System.out.println("handlerRemoved 被调用" + ctx.channel().id().asLongText());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("异样产生 " + cause.getMessage());
        ctx.close(); //敞开连贯
    }

}

html:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var socket;
//判断以后浏览器是否反对 websocket
if(window.WebSocket) {
//go on
socket = new WebSocket("ws://localhost:7000/hello");
//相当于 channelReado, ev 收到服务器端回送的音讯
socket.onmessage = function (ev) {
var rt = document.getElementById("responseText");
rt.value = rt.value + "\n" + ev.data;
}
//相当于连贯开启(感知到连贯开启)
socket.onopen = function (ev) {
var rt = document.getElementById("responseText");
rt.value = "连贯开启了.." }
//相当于连贯敞开(感知到连贯敞开)
socket.onclose = function (ev) {
var rt = document.getElementById("responseText");
rt.value = rt.value + "\n" + "连贯敞开了.." }
} else {
alert("以后浏览器不反对 websocket")
}
//发送音讯到服务器
function send(message) {
if(!window.socket) { //先判断 socket 是否创立好
return;
}
if(socket.readyState == WebSocket.OPEN) {
//通过 socket 发送音讯
socket.send(message)
} else {
alert("连贯没有开启");
}
}
</script>
<form onsubmit="return false">
<textarea name="message" style="height: 300px; width: 300px"></textarea>
<input type="button" value="产生音讯" onclick="send(this.form.message.value)">
<textarea id="responseText" style="height: 300px; width: 300px"></textarea>
<input type="button" value="清空内容" onclick="document.getElementById('responseText').value=''">
</form>
</body>
</html>

4.Netty外围模块组件剖析

咱们通过案例大抵学了一下Netty的应用，然而咱们还是只会api的调用，对于其中的每一个组件，以及每一个组件的原理，咱们都知之甚少，接下来咱们对每个组件都进行分析一番：

4.1）Bootstrap、ServerBootstrap

这是一个疏导类，一个Netty程序都是从Bootstrap开始的，次要作用是配置以及启动整个程序，串联所有netty的组件。Bootstrap是客户端的疏导类，ServerBootstrap是服务器端的疏导类。

4.2）Future,ChannelFuture

Netty所有的IO操作都是异步的，不能立即得悉音讯是否被解决。只能过一会儿等它执行实现，当操作胜利，应用程序天然就会监听到了。

4.3）channel
channel次要用于执行网络IO操作。
4.3.1）通过channel能够取得以后通道的状态。
4.3.2）通过channel能进行IO操作。
4.3.3）通过channel能取得缓冲区的大小

4.4）selector
Netty基于selector的I/O多路复用，通过selector一个线程能够监听多个链接的事件。

当一个selector中注册channel后，selector外部能够始终查问这些channel是否有就绪的I/O事件，这样程序就能够简略地应用一个线程高效治理多个channel。

4.5）channelHandler及其实现类
它是用来解决I/O工夫，并将其转发到ChannelPipeline(业务解决链路)的下一个处理程序。

咱们个别都定义一个Handler来减少咱们自定义的业务解决类。

4.6）Pipeline 和 ChannelPipeline
这是咱们次要的业务逻辑解决类，咱们通常通过继承类重写办法来退出咱们想要的业务逻辑。

4.7）ChannelHandlerContext
保留 Channel 相干的所有上下文信息，能够取得以后的channel等信息。

4.8）ChannelOption

Netty 在创立 Channel 实例后,个别都须要设置 ChannelOption 参数

4.9）EventLoopGroup 和其实现类 NioEventLoopGroup
是一组工作线程，Netty为了更好地利用多核cpu资源，个别会有多个EventLoop同时工作，每个EentLoop保护着一个seelctor实例。

4.10）Unpooled 类

Netty 提供一个专门用来操作缓冲区(即 Netty 的数据容器)的工具类。

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