引言：Netty是由JBOSS提供的一个java开源框架。Netty提供异步的、事件驱动的网络应用程序框架和工具，用以快速开发高性能、高可靠性的网络服务器和客户端程序。也就是说，Netty 是一个基于NIO的客户、服务器端编程框架，使用Netty 可以确保你快速和简单的开发出一个网络应用，例如实现了某种协议的客户，服务端应用。Netty相当简化和流线化了网络应用的编程开发过程，例如，TCP和UDP的socket服务开发。
下面我们就基于netty和tomcat实现一个websocket服务。(本示例基于maven构建，创建项目过程此处不再赘述)
项目依赖
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.12.Final</version>
</dependency>
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.1.3</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<!-- sevlet -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
服务端程序
首先重写ChannelInitializer的初始化方法
package com.mxpio.nettywebsocket.server;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.stream.ChunkedWriteHandler;
public class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel e) throws Exception {
e.pipeline().addLast("http-codec", new HttpServerCodec());
e.pipeline().addLast("aggregator", new HttpObjectAggregator(65536));
e.pipeline().addLast("http-chunked", new ChunkedWriteHandler());
e.pipeline().addLast("handler", new MyWebSocketServerHandler());
}
}
定义全局ChannelGroup
package com.mxpio.nettywebsocket.server;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;
public class Global {
public static ChannelGroup group = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
}
服务端核心类MyWebSocketServerHandler
package com.mxpio.nettywebsocket.server;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;
import com.mxpio.nettywebsocket.server.Global;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.codec.http.websocketx.CloseWebSocketFrame;
import io.netty.handler.codec.http.websocketx.PingWebSocketFrame;
import io.netty.handler.codec.http.websocketx.PongWebSocketFrame;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketServerHandshaker;
import io.netty.handler.codec.http.websocketx.WebSocketServerHandshakerFactory;
import io.netty.util.CharsetUtil;
public class MyWebSocketServerHandler extends SimpleChannelInboundHandler<Object> {
private static final Logger logger = Logger.getLogger(WebSocketServerHandshaker.class.getName());
private WebSocketServerHandshaker handshaker;
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
// 添加
Global.group.add(ctx.channel());
System.out.println("客户端与服务端连接开启");
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
// 移除
Global.group.remove(ctx.channel());
System.out.println("客户端与服务端连接关闭");
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
if (msg instanceof FullHttpRequest) {
handleHttpRequest(ctx, ((FullHttpRequest) msg));
} else if (msg instanceof WebSocketFrame) {
handlerWebSocketFrame(ctx, (WebSocketFrame) msg);
}
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
private void handlerWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame) {
// 判断是否关闭链路的指令
if (frame instanceof CloseWebSocketFrame) {
handshaker.close(ctx.channel(), (CloseWebSocketFrame) frame.retain());
}
// 判断是否ping消息
if (frame instanceof PingWebSocketFrame) {
ctx.channel().write(new PongWebSocketFrame(frame.content().retain()));
return;
}
// 本例程仅支持文本消息，不支持二进制消息
if (!(frame instanceof TextWebSocketFrame)) {
System.out.println("本例程仅支持文本消息，不支持二进制消息");
throw new UnsupportedOperationException(
String.format("%s frame types not supported", frame.getClass().getName()));
}
// 返回应答消息
String request = ((TextWebSocketFrame) frame).text();
System.out.println("服务端收到：" + request);
if (logger.isLoggable(Level.FINE)) {
logger.fine(String.format("%s received %s", ctx.channel(), request));
}
TextWebSocketFrame tws = new TextWebSocketFrame(new Date().toString() + ctx.channel().id() + "：" + request);
// 群发
Global.group.writeAndFlush(tws);
// 返回【谁发的发给谁】
// ctx.channel().writeAndFlush(tws);
}
private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest req) {
if (!req.decoderResult().isSuccess() || (!"websocket".equals(req.headers().get("Upgrade")))) {
sendHttpResponse(ctx, req,
new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.BAD_REQUEST));
return;
}
WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
"ws://localhost:7397/websocket", null, false);
handshaker = wsFactory.newHandshaker(req);
if (handshaker == null) {
WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
} else {
handshaker.handshake(ctx.channel(), req);
}
}
private static void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest req, DefaultFullHttpResponse res) {
// 返回应答给客户端
if (res.status().code() != 200) {
ByteBuf buf = Unpooled.copiedBuffer(res.status().toString(), CharsetUtil.UTF_8);
res.content().writeBytes(buf);
buf.release();
}
// 如果是非Keep-Alive，关闭连接
ChannelFuture f = ctx.channel().writeAndFlush(res);
if (!isKeepAlive(req) || res.status().code() != 200) {
f.addListener(ChannelFutureListener.CLOSE);
}
}
private static boolean isKeepAlive(FullHttpRequest req) {
return false;
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
启动器
1.java application方式启动
package com.mxpio.nettywebsocket.server;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
public class NettyServer {
public static void main(String[] args) {
new NettyServer().run();
}
public void run() {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workGroup);
b.channel(NioServerSocketChannel.class);
b.childHandler(new ChildChannelHandler());
System.out.println("服务端开启等待客户端连接 ... ...");
Channel ch = b.bind(7397).sync().channel();
ch.closeFuture().sync();
} catch (Exception e) {
e.printStackTrace();
} finally {
bossGroup.shutdownGracefully();
workGroup.shutdownGracefully();
}
}
}
2.在tomcat中基于listener启动
1.编写NettyListener继承ServletContextListener
package com.mxpio.nettywebsocket.listener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import com.mxpio.nettywebsocket.server.ChildChannelHandler;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
public class NettyListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
System.err.println("nettyListener Startup!");
new Thread() {
@Override
public void run() {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workGroup);
b.channel(NioServerSocketChannel.class);
b.childHandler(new ChildChannelHandler());
System.out.println("服务端开启等待客户端连接 ... ...");
Channel ch = b.bind(7397).sync().channel();
ch.closeFuture().sync();
} catch (Exception e) {
e.printStackTrace();
} finally {
bossGroup.shutdownGracefully();
workGroup.shutdownGracefully();
}
}
}.start();
System.err.println("nettyListener end!");
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
}
}
2.web.xml配置：
<listener>
<listener-class>com.mxpio.nettywebsocket.listener.NettyListener</listener-class>
</listener>
测试客户端web页面
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>websocket演示</title>
</head>
</head>
<script type="text/javascript">
var socket;
if (!window.WebSocket) {
window.WebSocket = window.MozWebSocket;
}
if (window.WebSocket) {
socket = new WebSocket("ws://localhost:7397/websocket");
socket.onmessage = function(event) {
var ta = document.getElementById('responseText');
ta.value += event.data + "\r\n";
};
socket.onopen = function(event) {
var ta = document.getElementById('responseText');
ta.value = "打开WebSoket 服务正常，浏览器支持WebSoket!" + "\r\n";
};
socket.onclose = function(event) {
var ta = document.getElementById('responseText');
ta.value = "";
ta.value = "WebSocket 关闭" + "\r\n";
};
} else {
alert("您的浏览器不支持WebSocket协议！");
}
function send(message) {
if (!window.WebSocket) {
return;
}
if (socket.readyState == WebSocket.OPEN) {
socket.send(message);
} else {
alert("WebSocket 连接没有建立成功！");
}
}
</script>
<body>
<form onSubmit="return false;">
<input type="text" name="message" value="Netty The Sinper" /> <br />
<br /> <input type="button" value="发送 WebSocket 请求消息"
onClick="send(this.form.message.value)" />
<hr color="blue" />
<h3>服务端返回的应答消息</h3>
<textarea id="responseText" style="width: 1024px; height: 300px;"></textarea>
</form>
</body>
</html>
至此，一个简单的webSocket示例就完成了。
