手写Netty实现的网络服务

文章目录

  • TCP服务Demo
  • HTTP服务器Demo
  • 群聊聊天室Demo
  • WebSocket长连接Demo
  • 自定义编解码器Demo
  • 手写一个RPC

TCP服务Demo

服务端:

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

        //创建BossGroup和WorkerGroup
        //BossGroup只是处理连接请求,真正的和客户端业务处理会交给WorkerGroup完成
        //BossGroup和WorkerGroup含有的子线程(NioEventLoop)的个数默认实际CPU核数 * 2
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup(); //8

        try {
            //创建服务器端的启动对象,配置参数
            ServerBootstrap bootstrap = new ServerBootstrap();

            //使用链式编程来进行设置
            bootstrap.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class) 
                .option(ChannelOption.SO_BACKLOG, 128) //设置线程队列得到连接个数
                .childOption(ChannelOption.SO_KEEPALIVE, true) //设置保持活动连接状态
//              .handler(null) //该handler对应BossGroup,childHandler对应WorkerGroup
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    //给pipeline设置处理器
                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        ch.pipeline().addLast(new NettyServerHandler());
                    }
                }); //给WorkerGroup的EventLoop对应的管道设置处理器

            System.out.println(".....服务器 is ready...");

            //启动服务器(并绑定端口)
            ChannelFuture cf = bootstrap.bind(6668).sync();

            //给cf注册监听器,监控我们关心的事件
            cf.addListener(new ChannelFutureListener() {
                @Override
                public void operationComplete(ChannelFuture future) throws Exception {
                    if (cf.isSuccess()) {
                        System.out.println("监听端口 6668 成功");
                    } else {
                        System.out.println("监听端口 6668 失败");
                    }
                }
            });
            //对关闭通道进行监听
            cf.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

class NettyServerHandler extends ChannelInboundHandlerAdapter {


    //ChannelHandlerContext ctx:上下文对象,含有管道pipeline,通道channel,地址
    //Object msg: 就是客户端发送的数据,默认为Object
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

        Channel channel = ctx.channel();
        ChannelPipeline pipeline = ctx.pipeline(); //本质是一个双向链接, 出站入站

        //将msg转成一个ByteBuf,ByteBuf是Netty提供的,不是NIO的ByteBuffer
        ByteBuf buf = (ByteBuf) msg;
        System.out.println("客户端发送消息是:" + buf.toString(CharsetUtil.UTF_8));
        System.out.println("客户端地址:" + channel.remoteAddress());
    }

    //数据读取完毕
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

        //writeAndFlush是write + flush,将数据写入到缓存,并刷新
        ctx.writeAndFlush(Unpooled.copiedBuffer("hello, 客户端", CharsetUtil.UTF_8));
    }

    //处理异常, 一般是需要关闭通道
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }
}

客户端:

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

        //客户端需要一个事件循环组,不需要主从Reactor
        EventLoopGroup group = new NioEventLoopGroup();

        try {
            //创建客户端启动对象,注意客户端使用的不是ServerBootstrap而是Bootstrap
            Bootstrap bootstrap = new Bootstrap();

            bootstrap.group(group) //设置线程组
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        ch.pipeline().addLast(new NettyClientHandler()); //加入自己的处理器
                    }
                });

            System.out.println("客户端 ok..");

            //启动客户端去连接服务器端型
            ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 6668).sync();
            //给关闭通道进行监听
            channelFuture.channel().closeFuture().sync();
        }finally {
            group.shutdownGracefully();
        }
    }
}

class NettyClientHandler extends ChannelInboundHandlerAdapter {

    //当通道就绪就会触发该方法
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("client " + ctx);
        ctx.writeAndFlush(Unpooled.copiedBuffer("hello, server", CharsetUtil.UTF_8));
    }

    //当通道有读取事件时,会触发
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

        ByteBuf buf = (ByteBuf) msg;
        System.out.println("服务器回复的消息:" + buf.toString(CharsetUtil.UTF_8));
        System.out.println("服务器的地址: "+ ctx.channel().remoteAddress());
    }

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

HTTP服务器Demo

服务端:

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

        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.
                group(bossGroup, workerGroup).
                channel(NioServerSocketChannel.class).
                childHandler(new HttpServerInitializer());

            ChannelFuture channelFuture = serverBootstrap.bind(6668).sync();          
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

class HttpServerInitializer extends ChannelInitializer<SocketChannel> {

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

        //向管道加入处理器
        ChannelPipeline pipeline = ch.pipeline();

        //HttpServerCodec是Netty提供的处理http的编-解码器
        pipeline.addLast("MyHttpServerCodec", new HttpServerCodec());
        //增加一个自定义的Handler
        pipeline.addLast("MyTestHttpServerHandler", new HttpServerHandler());
    }
}

/*
SimpleChannelInboundHandler是ChannelInboundHandlerAdapter
客户端和服务器端相互通讯的数据被封装成HttpObject
 */
class HttpServerHandler extends SimpleChannelInboundHandler<HttpObject> {

    //channelRead0读取客户端数据
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
        
        //判断msg是不是Httprequest请求
        if(msg instanceof HttpRequest) {
            
            HttpRequest httpRequest = (HttpRequest) msg;
            //获取uri, 过滤指定的资源
            URI uri = new URI(httpRequest.uri());
            if("/favicon.ico".equals(uri.getPath())) {
                System.out.println("请求了 favicon.ico, 不做响应");
                return;
            }
            
            //回复信息给浏览器[http协议]
            ByteBuf content = Unpooled.copiedBuffer("我是服务器", CharsetUtil.UTF_8);

            //构造一个Http的响应,即HttpResponse
            FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, content);
            response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain");
            response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes());
            //将构建好的response返回
            ctx.writeAndFlush(response);
        }
    }
}

群聊聊天室Demo

服务端:

public class GroupChatServer {

    private int port; //监听端口

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

    //编写run方法,处理客户端的请求
    public void run() throws  Exception{

        //创建两个线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup(); //8个NioEventLoop

        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)
                .option(ChannelOption.SO_BACKLOG, 128)
                .childOption(ChannelOption.SO_KEEPALIVE, true)
                .childHandler(new ChannelInitializer<SocketChannel>() {

                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        //获取到pipeline
                        ChannelPipeline pipeline = ch.pipeline();
                        //向pipeline加入解码器
                        pipeline.addLast("decoder", new StringDecoder());
                        //向pipeline加入编码器
                        pipeline.addLast("encoder", new StringEncoder());
                        //加入自己的业务处理handler
                        pipeline.addLast(new GroupChatServerHandler());
                    }
                });

            System.out.println("Netty服务器启动");
            ChannelFuture channelFuture = b.bind(port).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        new GroupChatServer(7000).run();
    }
}

class GroupChatServerHandler extends SimpleChannelInboundHandler<String> {

    //定义一个channle组,管理所有的channel
    //GlobalEventExecutor.INSTANCE是全局的事件执行器,是一个单例
    private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");


    //handlerAdded表示连接建立,一旦连接,第一个被执行    
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        
        //将该客户加入聊天的信息推送给其它在线的客户端
        channelGroup.writeAndFlush("[客户端]" + channel.remoteAddress() + " 加入聊天" + sdf.format(new java.util.Date()) + " \n");
        
        //将当前Channel加入到ChannelGroup
        channelGroup.add(channel);
    }

    //断开连接, 将xx客户离开信息推送给当前在线的客户
    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        channelGroup.writeAndFlush("[客户端]" + channel.remoteAddress() + " 离开了\n");
        // ChannelGroup自动移除该Channel
        System.out.println("channelGroup size" + channelGroup.size());
    }

    //表示Channel处于活动状态, 提示xx上线
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + " 上线了~");
    }

    //表示Channel处于不活动状态, 提示xx离线了
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + " 离线了~");
    }

    //读取数据
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        
        Channel channel = ctx.channel();
        
        //这时我们遍历ChannelGroup, 根据不同的情况,回送不同的消息
        channelGroup.forEach(ch -> {
            if(channel != ch) { //不是当前的channel,转发消息
                ch.writeAndFlush("[客户]" + channel.remoteAddress() + " 发送了消息" + msg + "\n");
            }else {//回显自己发送的消息给自己
                ch.writeAndFlush("[自己]发送了消息" + msg + "\n");
            }
        });
    }

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

客户端:

public class GroupChatClient {

    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 {
                        ChannelPipeline pipeline = ch.pipeline();
                        pipeline.addLast("decoder", new StringDecoder());
                        pipeline.addLast("encoder", new StringEncoder());
                        pipeline.addLast(new GroupChatClientHandler());
                    }
                });

            ChannelFuture channelFuture = bootstrap.connect(host, port).sync();
            
            //得到channel
            Channel channel = channelFuture.channel();
            System.out.println("-------" + channel.localAddress()+ "--------");
            //客户端需要输入信息,创建一个扫描器
            Scanner scanner = new Scanner(System.in);
            while (scanner.hasNextLine()) {
                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", 7000).run();
    }
}

class GroupChatClientHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(msg.trim());
    }
}

WebSocket长连接Demo

服务端:

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

        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup(); //8个NioEventLoop
        try {

            ServerBootstrap serverBootstrap = new ServerBootstrap();

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

                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ChannelPipeline pipeline = ch.pipeline();

                    //因为基于http协议,使用http的编码和解码器
                    pipeline.addLast(new HttpServerCodec());
                    
                    //是以块方式写,添加ChunkedWriteHandler处理器
                    pipeline.addLast(new ChunkedWriteHandler());                   
                    
                    //Http数据在传输过程中是分段的, HttpObjectAggregator可以将多个段聚合
                    pipeline.addLast(new HttpObjectAggregator(8192));

                    //浏览器请求时ws://localhost:7000/hello表示请求的uri
                    //WebSocketServerProtocolHandler核心功能是将Http协议升级为ws协议,保持长连接
                    pipeline.addLast(new WebSocketServerProtocolHandler("/hello2"));

                    //自定义的handler,处理业务逻辑
                    pipeline.addLast(new MyWebSocketFrameHandler());
                }
            });

            //启动服务器
            ChannelFuture channelFuture = serverBootstrap.bind(7000).sync();
            channelFuture.channel().closeFuture().sync();

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

class MyWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame>{
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {

        System.out.println("服务器收到消息 " + msg.text());
        //回复消息
        ctx.channel().writeAndFlush(new TextWebSocketFrame("服务器时间" + LocalDateTime.now() + " " + msg.text()));
    }

    //当web客户端连接后,触发方法
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        //id 表示唯一的值,LongText是唯一的而ShortText不是唯一
        System.out.println("handlerAdded 被调用" + ctx.channel().id().asLongText());
        System.out.println("handlerAdded 被调用" + ctx.channel().id().asShortText());
    }

    @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("异常发生 " + cause.getMessage());
        ctx.close(); //关闭连接
    }
}

客户端:


<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Titletitle>
head>
<body>
<script>
    var socket;
    //判断当前浏览器是否支持websocket
    if(window.WebSocket) {
        //go on
        socket = new WebSocket("ws://localhost:7000/hello2");
        //相当于channelReado, ev收到服务器端回送的消息
        socket.onmessage = function (ev) {
            var rt = document.getElementById("responseText");
            rt.value = rt.value + "\n" + ev.data;
        }

        //相当于连接开启(感知到连接开启)
        socket.onopen = function (ev) {
            var rt = document.getElementById("responseText");
            rt.value = "连接开启了.."
        }

        //相当于连接关闭(感知到连接关闭)
        socket.onclose = function (ev) {
            var rt = document.getElementById("responseText");
            rt.value = rt.value + "\n" + "连接关闭了.."
        }
    } else {
        alert("当前浏览器不支持websocket")
    }

    //发送消息到服务器
    function send(message) {
        if(!window.socket) { //先判断socket是否创建好
            return;
        }
        if(socket.readyState == WebSocket.OPEN) {
            //通过socket发送消息
            socket.send(message)
        } else {
            alert("连接没有开启");
        }
    }
script>
    <form onsubmit="return false">
        <textarea name="message" style="height: 300px; width: 300px">textarea>
        <input type="button" value="发生消息" 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>

自定义编解码器Demo

Handler链的调用机制:

不论解码器handler,还是编码器handler,接收的消息类型必须与待处理的消息类型一致,否则该handler不
会被执行。同时InboundHandler与OutboundHandler互不影响。

手写Netty实现的网络服务_第1张图片

使用自定义的编码器和解码器来说明Netty的handler调用机制:

  • 客户端发送long -> 服务器
  • 服务端发送long -> 客户端

Long类型的自定义编解码器:

public class MyByteToLongDecoder extends ByteToMessageDecoder {
    /**
     * decode会根据接收的数据,被调用多次, 直到确定没有新的元素被添加到list或者是ByteBuf没有更多的可读
     * 字节为止
     * 如果list out不为空,就会将list的内容传递给下一个channelinboundhandler处理, 该处理器的方法也
     * 会被调用多次
     *
     * @param ctx 上下文对象
     * @param in 入站的ByteBuf
     * @param out List集合,将解码后的数据传给下一个handler
     * @throws Exception
     */
    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        //因为long8个字节, 需要判断有8个字节,才能读取一个long
        if(in.readableBytes() >= 8) {
            out.add(in.readLong());
        }
    }
}

public class MyLongToByteEncoder extends MessageToByteEncoder<Long> {
    //编码方法
    @Override
    protected void encode(ChannelHandlerContext ctx, Long msg, ByteBuf out) throws Exception {
        System.out.println("msg=" + msg);
        out.writeLong(msg);
    }
}

服务端:

public class MyServer {
    public static void main(String[] args) throws Exception{
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup()
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workerGroup)
                .channel(NioServerSocketChannel.class)
                .childHandler(new MyServerInitializer()); //自定义一个初始化类

            ChannelFuture channelFuture = serverBootstrap.bind(7000).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

class MyServerInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();

        //入站的handler进行解码MyByteToLongDecoder
        pipeline.addLast(new MyByteToLongDecoder());
        //出站的handler进行编码
        pipeline.addLast(new MyLongToByteEncoder());
        //自定义的handler处理业务逻辑
        pipeline.addLast(new MyServerHandler());
    }
}

class MyServerHandler extends SimpleChannelInboundHandler<Long> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Long msg) throws Exception {
        System.out.println("从客户端读取到long " + msg);
        //给客户端发送一个long
        ctx.writeAndFlush(98765L);
    }

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

客户端:

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

        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(group)
                .channel(NioSocketChannel.class)
                .handler(new MyClientInitializer()); //自定义一个初始化类

            ChannelFuture channelFuture = bootstrap.connect("localhost", 7000).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            group.shutdownGracefully();
        }
    }
}

class MyClientInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        //加入一个出站的handler,对数据进行编码
        pipeline.addLast(new MyLongToByteEncoder());

        pipeline.addLast(new MyByteToLongDecoder());
        pipeline.addLast(new MyClientHandler());
    }
}

class MyClientHandler  extends SimpleChannelInboundHandler<Long> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Long msg) throws Exception {
        System.out.println("服务器的ip=" + ctx.channel().remoteAddress());
        System.out.println("收到服务器消息=" + msg);
    }

    //重写channelActive 发送数据
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("MyClientHandler 发送数据");
        //ctx.writeAndFlush(Unpooled.copiedBuffer(""))
        ctx.writeAndFlush(123456L); //发送的是一个long
    }
}

手写一个RPC

RPC调用流程图:

手写Netty实现的网络服务_第2张图片

Dubbo底层使用了Netty作为网络通讯框架,使用Netty实现一个简单的RPC框架。

模仿Dubbo,消费者和提供者约定接口和协议,消费者远程调用提供者的服务,提供者返回一个字符串,消费者打印提供者返回的数据。底层网络通信使用Netty 4.1.20。

公共的接口:

// 这个是接口,服务提供方和服务消费方都需要依赖
public interface HelloService {
    String hello(String mes);
}

服务端:

接口的真正实现:

public class HelloServiceImpl implements HelloService{

    @Override
    public String hello(String mes) {
        System.out.println("收到客户端消息=" + mes);
        // 根据mes返回不同的结果
        if(mes != null) {
            return "你好客户端, 我已经收到你的消息 [" + mes + "] ";
        } else {
            return "你好客户端, 我已经收到你的消息 ";
        }
    }
}

服务端的实现:

public class NettyServer {

    public static void startServer(String hostName, int port) {
        startServer0(hostName,port);
    }

    //编写一个方法,完成对NettyServer的初始化和启动
    private static void startServer0(String hostname, int port) {

        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        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) throws Exception {
                          ChannelPipeline pipeline = ch.pipeline();
                          pipeline.addLast(new StringDecoder());
                          pipeline.addLast(new StringEncoder());
                          pipeline.addLast(new NettyServerHandler()); //业务处理器
                      }
                }
            );

            ChannelFuture channelFuture = serverBootstrap.bind(hostname, port).sync();
            System.out.println("服务提供方开始提供服务~~");
            channelFuture.channel().closeFuture().sync();

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

//服务器这边handler比较简单
class NettyServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        //客户端在调用服务器的API时,需要定义一个协议
        if(msg.toString().startsWith(ClientBootstrap.providerName)) {
            String result = new HelloServiceImpl().hello(msg.toString().substring(msg.toString().lastIndexOf("#") + 1));
            ctx.writeAndFlush(result);
        }
    }

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

客户端:

客户端调用RPC的方法:

public class ClientBootstrap {

    //这里定义协议头
    public static final String providerName = "HelloService#hello#";

    public static void main(String[] args) throws  Exception{
        //创建一个消费者
        NettyClient customer = new NettyClient();
        //创建代理对象
        HelloService service = (HelloService) customer.getBean(HelloService.class, providerName);
        for (;; ) {
            Thread.sleep(2 * 1000);
            //通过代理对象调用服务提供者的方法(服务)
            String res = service.hello("你好 dubbo~");
            System.out.println("调用的结果res= " + res);
        }
    }
}

NettyClient的实现:

public class NettyClient {

    //创建线程池
    private static ExecutorService executor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());

    private static NettyClientHandler client;

    //编写方法使用代理模式,获取一个代理对象
    public Object getBean(final Class<?> serivceClass, final String providerName) {
        return Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(),
            new Class<?>[]{serivceClass}, (proxy, method, args) -> {
                //客户端每调用一次hello, 就会进入到该handler代码中
                if (client == null) {
                    initClient();
                }
                //设置要发给服务器端的信息:(providerName是协议头)
                client.setPara(providerName + args[0]);
                return executor.submit(client).get();
            });
    }

    //初始化客户端
    private static void initClient() {
        client = new NettyClientHandler();
        //创建EventLoopGroup
        NioEventLoopGroup group = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(group)
            .channel(NioSocketChannel.class)
            .option(ChannelOption.TCP_NODELAY, true)
            .handler(
                new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        ChannelPipeline pipeline = ch.pipeline();
                        pipeline.addLast(new StringDecoder());
                        pipeline.addLast(new StringEncoder());
                        pipeline.addLast(client);
                    }
                }
            );

        try {
            bootstrap.connect("127.0.0.1", 7000).sync();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

class NettyClientHandler extends ChannelInboundHandlerAdapter implements Callable {

    private ChannelHandlerContext context;//上下文
    private String result; //返回的结果
    private String para; //客户端调用方法时,传入的参数
    
    void setPara(String para) {
        this.para = para;
    }

    //与服务器的连接创建后,就会被调用, 这个方法是第一个被调用(1)
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(" channelActive 被调用...");
        context = ctx; //因为我们在其它方法会使用到ctx
    }

    //收到服务器的数据后,调用方法。(3)
    @Override
    public synchronized void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println(" channelRead 被调用...");
        result = msg.toString();
        notify(); //唤醒等待的线程
    }

    //被代理对象调用, 发送数据给服务器,-> wait -> 等待被唤醒(channelRead) -> 返回结果。(2)
    @Override
    public synchronized Object call() throws Exception {
        System.out.println("call 被调用...");
        context.writeAndFlush(para);
        wait(); //等待channelRead 方法获取到服务器的结果后,唤醒
        return result; //服务方返回的结果
    }
    
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }
}

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