009-核心技术-netty-通过WebSocket编程实现服务器和客户端长连接


一、长连接

http协议是无状态的,浏览器和服务器间的请求相应一次,下一次会重新创建连接

1、服务端代码


package com.github.bjlhx15.netty.demo.netty.websocket;

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 {
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup bossGroup = new NioEventLoopGroup(1);
NioEventLoopGroup workerGroup = new NioEventLoopGroup();

try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.handler(new LoggingHandler(LogLevel.INFO))//在bossGroup增加一个日志处理器
.option(ChannelOption.SO_BACKLOG, 128)
.childOption(ChannelOption.SO_KEEPALIVE, true)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
//基于http协议 使用http编解码
pipeline.addLast(new HttpServerCodec());
// 是以块方式写,添加ChunkedWriteHandler处理器
pipeline.addLast(new ChunkedWriteHandler());
// http数据是分段的,HttpObjectAggregator 是将多个端聚合
pipeline.addLast(new HttpObjectAggregator(8192));
// 对于websocket,数据是以帧(frame)形式传递
// WebSocketFrame下有六个子类
// 浏览器请求时:ws://localhost:7000/hello 表示请求的URI
// WebSocketServerProtocolHandler 核心时将http协议升级为ws协议,保持长连接
// 是通过状态码 101切换的,请求地址要匹配
pipeline.addLast(new WebSocketServerProtocolHandler("/hello"));
pipeline.addLast(new MyTextWebSocketFrameHandler());
}
});
ChannelFuture channelFuture = serverBootstrap.bind(7000).sync();

System.out.println("Server start listen at " + 7000);
channelFuture.channel().closeFuture().sync();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}



服务端handler


package com.github.bjlhx15.netty.demo.netty.websocket;

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

import java.time.LocalDateTime;

//TextWebSocketFrame表示一个文本帧
public class MyTextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
@Override
protected void channelRead0(ChannelHandlerContext channelHandlerContext, TextWebSocketFrame textWebSocketFrame) throws Exception {
System.out.println("服务端收到消息:" + textWebSocketFrame.text());
//回复
channelHandlerContext.channel().writeAndFlush(new TextWebSocketFrame("服务器事件:"
+ LocalDateTime.now() + " " + textWebSocketFrame.text()));
}

@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
//id 表示唯一至,asLongText是唯一的,asShortText不是唯一的
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("handlerRemoved 被调用:" + cause.getMessage());
ctx.close();
}
}



客户端页面


<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form onsubmit="return false">
<textarea name="message" style="height: 300px;width: 300px"></textarea>
<input type="button" value="发送消息" 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>
<script>
var socket;
if (window.WebSocket) {
socket = new WebSocket("ws://localhost:7000/hello");
socket.onmessage = function (ev) {
let rt = document.getElementById("responseText");
rt.value = rt.value + "\n" + ev.data;
}
socket.onopen = function (ev) {
let rt = document.getElementById("responseText");
rt.value = "连接开启";
}
socket.onclose = function (ev) {
let rt = document.getElementById("responseText");
rt.value = rt.value + "\n" + "连接关闭";
}
} else {
alert("浏览器不支持");
}

function send(msg) {
if (!window.socket) {
return;
}
if (socket.readyState == WebSocket.OPEN) {
socket.send(msg);
} else {
alert("连接没有开启")
}

}
</script>
</html>

使用idea run下main以及html即可调试。


作者:李宏旭