什么是Netty
- 高性能事件驱动、异步非阻塞；基于Netty可以建立高性能的HTTP服务器。
- 基于NIO的客户端，服务器端编程框架；可以快速简单开发网络应用，比如TCP/UDP的socket网络开发。
- 稳定性和伸缩性
Netty使用场景
BIO通信
BIO通信模型
伪异步IO通信
伪异步IO通信模型
NIO通信
- 缓冲区Buffer
- 通道Channel
- 多路复用器Selector
AIO通信
- 连接注册读写事件和回调函数
- 读写方法异步
- 主动通知程序
四种IO对比
- 客户端个数
- IO类型（按顺序依次为：阻塞同步IO、阻塞同步IO、非阻塞同步IO、非阻塞异步IO）
- API使用难度
- 调试难度
- 可靠性
- 吞吐量
原生NIO的缺陷
- 类库和API繁杂
- 工作量和难度大
- 入门门槛高
- JDK NIO存在bug
Netty的优势
WebSocket入门
什么是WebSocket？
- H5协议规范
- 握手机制
- 解决客户端与服务端实时通信而产生的技术
WebSocket的优点
- 节省通信开销
- 服务器主动传送数据给客户端
- 实时通信
WebSocket建立连接
WebSocket生命周期
WebSocket连接关闭
- 服务器关闭底层TCP连接
- 客户端发起TCP Close
Netty实现WebSocket通信案例
服务端
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;
/**
* 存储整个工程的全局配置
* @author liuyazhuang
*
*/
public class NettyConfig {
/**
* 存储每一个客户端接入进来时的channel对象
*/
public static ChannelGroup group = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
}
import java.util.Date;
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;
/**
* 接收/处理/响应客户端websocket请求的核心业务处理类
* @author liuyazhuang
*
*/
public class MyWebSocketHandler extends SimpleChannelInboundHandler<Object> {
private WebSocketServerHandshaker handshaker;
private static final String WEB_SOCKET_URL = "ws://localhost:8888/websocket";
// 客户端与服务端创建连接的时候调用
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
NettyConfig.group.add(ctx.channel());
System.out.println("客户端与服务端连接开启...");
}
// 客户端与服务端断开连接的时候调用
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
NettyConfig.group.remove(ctx.channel());
System.out.println("客户端与服务端连接关闭...");
}
// 服务端接收客户端发送过来的数据结束之后调用
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
// 工程出现异常的时候调用
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
// 服务端处理客户端websocket请求的核心方法
@Override
protected void messageReceived(ChannelHandlerContext context, Object msg) throws Exception {
// 处理客户端向服务端发起http握手请求的业务
if (msg instanceof FullHttpRequest) {
handHttpRequest(context, (FullHttpRequest)msg);
}else if (msg instanceof WebSocketFrame) { //处理websocket连接业务
handWebsocketFrame(context, (WebSocketFrame)msg);
}
}
/**
* 处理客户端与服务端之前的websocket业务
* @param ctx
* @param frame
*/
private void handWebsocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame){
// 判断是否是关闭websocket的指令
if (frame instanceof CloseWebSocketFrame) {
handshaker.close(ctx.channel(), (CloseWebSocketFrame)frame.retain());
}
// 判断是否是ping消息
if (frame instanceof PingWebSocketFrame) {
ctx.channel().write(new PongWebSocketFrame(frame.content().retain()));
return;
}
// 判断是否是二进制消息，如果是二进制消息，抛出异常
if( ! (frame instanceof TextWebSocketFrame) ){
System.out.println("目前我们不支持二进制消息");
throw new RuntimeException("【"+this.getClass().getName()+"】不支持消息");
}
// 返回应答消息
// 获取客户端向服务端发送的消息
String request = ((TextWebSocketFrame) frame).text();
System.out.println("服务端收到客户端的消息====>>>" + request);
TextWebSocketFrame tws = new TextWebSocketFrame(new Date().toString()
+ ctx.channel().id()
+ " ===>>> "
+ request);
// 群发，服务端向每个连接上来的客户端群发消息
NettyConfig.group.writeAndFlush(tws);
}
/**
* 处理客户端向服务端发起http握手请求的业务
* @param ctx
* @param req
*/
private void handHttpRequest(ChannelHandlerContext ctx, FullHttpRequest req){
if (!req.getDecoderResult().isSuccess()
|| ! ("websocket".equals(req.headers().get("Upgrade")))) {
sendHttpResponse(ctx, req,
new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.BAD_REQUEST));
return;
}
WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
WEB_SOCKET_URL, null, false);
handshaker = wsFactory.newHandshaker(req);
if (handshaker == null) {
WebSocketServerHandshakerFactory.sendUnsupportedWebSocketVersionResponse(ctx.channel());
}else{
handshaker.handshake(ctx.channel(), req);
}
}
/**
* 服务端向客户端响应消息
* @param ctx
* @param req
* @param res
*/
private void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest req,
DefaultFullHttpResponse res){
if (res.getStatus().code() != 200) {
ByteBuf buf = Unpooled.copiedBuffer(res.getStatus().toString(), CharsetUtil.UTF_8);
res.content().writeBytes(buf);
buf.release();
}
// 服务端向客户端发送数据
ChannelFuture f = ctx.channel().writeAndFlush(res);
if (res.getStatus().code() != 200) {
f.addListener(ChannelFutureListener.CLOSE);
}
}
}
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;
/**
* 初始化连接时候的各个组件
* @author liuyazhuang
*
*/
public class MyWebSocketChannelHandler 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 MyWebSocketHandler());
}
}
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;
/**
* 程序的入口，负责启动应用
* @author liuyazhuang
*
*/
public class Main {
public static void main(String[] args) {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workGroup);
b.channel(NioServerSocketChannel.class);
b.childHandler(new MyWebSocketChannelHandler());
System.out.println("服务端开启等待客户端连接....");
Channel ch = b.bind(8888).sync().channel();
ch.closeFuture().sync();
} catch (Exception e) {
e.printStackTrace();
}finally{
//优雅的退出程序
bossGroup.shutdownGracefully();
workGroup.shutdownGracefully();
}
}
}
客户端
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset = utf-8"/>
<title>WebSocket客户端</title>
<script type="text/javascript">
var socket;
if(!window.WebSocket){
window.WebSocket = window.MozWebSocket;
}
if(window.WebSocket){
socket = new WebSocket("ws://localhost:8888/websocket");
socket.onmessage = function(event){
var ta = document.getElementById('responseContent');
ta.value += event.data + "\r\n";
};
socket.onopen = function(event){
var ta = document.getElementById('responseContent');
ta.value = "你当前的浏览器支持WebSocket,请进行后续操作\r\n";
};
socket.onclose = function(event){
var ta = document.getElementById('responseContent');
ta.value = "";
ta.value = "WebSocket连接已经关闭\r\n";
};
}else{
alert("您的浏览器不支持WebSocket");
}
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>
</head>
<body>
<form onSubmit="return false;">
<input type = "text" name = "message" value = ""/>
<br/><br/>
<input type = "button" value = "发送WebSocket请求消息" onClick = "send(this.form.message.value)"/>
<hr color="red"/>
<h2>客户端接收到服务端返回的应答消息</h2>
<textarea id = "responseContent" style = "width:1024px; height:300px"></textarea>
</form>
</body>
</html>
网友评论