Netty由淺到深_第五章_Netty通過WebSocket實現服務器和客戶端長連接

1）Http協議是無狀態的，瀏覽器和服務器間的請求響應一次，下一次會重新創建連接
2）要求：實現基於WebSocket的長連接的全雙工交互
3）改變Http協議多次請求的約束，實現長連接，服務器可以發送消息給瀏覽器
4）客戶端瀏覽器和服務器端會相互感知，比如服務器關閉了，瀏覽器會感知，同樣瀏覽器關閉了，服務器會感知

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var socket;;
    //判斷當前瀏覽器是否支持Websocket通訊
    if (window.WebSocket){
        //go on
        socket = new WebSocket("ws://localhost:7000/hello")
        //相當於channelRead0, ev 收到服務器端回送的消息
        socket.onmessage = function (ev) {
            var rt = document.getElementById("responseText")
            rt.value = rt.value + "\n" + ev.data;
        }
        //相當於連接開始
        socket.onopen = function (ev) {
            var rt = document.getElementById("responseText")
            rt.value = "連接開啓了。。。。。。。。" ;
        }
        socket.onclose = function (ev) {
            var rt = document.getElementById("responseText")
            rt.value = rt.value + "\n"+"連接關閉了了。。。。。。。。" ;
        }

    }else {
        alert("當前瀏覽器不支持webSocket編程")
    }

    //發送消息到服務器
    function send(msg) {
        if (!window.socket){//判斷socket是否創建好
            return;
        }
        if (socket.readyState == WebSocket.OPEN){
            //通過socket發送消息
            socket.send(msg)
        }else {
            alert("連接未開啓")
        }
    }
</script>
    <form onsubmit="return false">
        <textarea name="message" style="height: 300px;width: 300px"></textarea>
        <input type="button" value="發生消息" onclick="send(this.form.message.value)">
        <textarea id="responseText" style="height: 300px;width: 300px"></textarea>
        <input type="button" value="清空內容"  onclick="document.getElementById('responseText').value=''">
    </form>

</body>
</html>

package com.dd.netty.websocket;

import com.dd.netty.heartbeat.MyServerHandler;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
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;

public class MyServer {

    private int port ;//監聽端口

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

    public void run() throws InterruptedException {
        //創建bossGroup和WrokerGroup
        NioEventLoopGroup bossGroup = new NioEventLoopGroup(1);
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();//默認cpu核數乘以2個NioEventLoop
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(bossGroup,workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))//在boosGroup 增加一個日誌處理器
                    .option(ChannelOption.SO_BACKLOG,128)
                    .childOption(ChannelOption.SO_KEEPALIVE,true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {

                            ChannelPipeline pipeline = socketChannel.pipeline();

                            //因爲基於http協議，使用http的編解碼器
                            pipeline.addLast(new HttpServerCodec());

                            //是以塊的方式寫的，添加chunkedWrite處理器
                            pipeline.addLast(new ChunkedWriteHandler());

                            //HttpObjectAggregator
                            /*
                            1.http數據在傳輸過程中是分段的，HttpObjectAggregator，就是可以將多個段聚合起來
                            2.這就是爲什麼當瀏覽器發送大量數據時，就會發出多次http請求的原因
                             */
                            pipeline.addLast(new HttpObjectAggregator(8192));

                            /*
                            1.對於webSocket,他的數據是以 幀（frame）形式傳遞
                            2.可以看到webSocketFrame下面有6個子類
                            3.瀏覽器發送請求時地址 ws://localhost:7000/xxx   xxx表示請求的uri
                            4.WebSocketServerProtocolHandler的核心功能爲將Http協議升級爲ws協議，即webSocket協議，保持長連接
                            5.是通過一個狀態碼 101
                             */
                            pipeline.addLast(new WebSocketServerProtocolHandler("/hello"));

                            //自定義handler,處理業務邏輯
                            pipeline.addLast(new MyTestWebSocketFrameHandler());
                        }
                    });

            System.out.println("Netty服務器啓動");

            ChannelFuture chanelFuture = bootstrap.bind(port).sync();

            //監聽關閉事件
            chanelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }


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

package com.dd.netty.websocket;

import com.sun.org.apache.bcel.internal.generic.NEW;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;

import java.text.SimpleDateFormat;
import java.time.LocalDateTime;

//TextWebSocketFrame表示一個文本幀(frame)
public class MyTestWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, TextWebSocketFrame msg) throws Exception {
        System.out.println("服務器段收到消息"+msg.text());

        //回覆瀏覽器
        channelHandlerContext.writeAndFlush(new TextWebSocketFrame("服務器時間"+ LocalDateTime.now()+"消息爲"+msg.text()));

    }

    //當web客戶端連接後，就會觸發該方法
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        //id表示唯一的值，
        System.out.println("handlerAdded被調用"+ctx.channel().id().asLongText());

        //該id不是唯一的值，
        System.out.println("handlerAdded被調用"+ctx.channel().id().asShortText());
    }


    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        //id表示唯一的值，
        System.out.println("handlerAdded被調用"+ctx.channel().id().asLongText());

        //該id不是唯一的值，
        System.out.println("handlerAdded被調用"+ctx.channel().id().asShortText());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("異常發生" +cause.getMessage());

        ctx.close();
    }
}

Netty由淺到深_第五章_Netty通過WebSocket實現服務器和客戶端長連接

Netty由淺到深_第五章_Netty通過WebSocket實現服務器和客戶端長連接

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