Netty + websocket聊天室
程序处理逻辑
图1.png
启用websocket
从标准的HTTP或者HTTPS协议切换到WebSocket时，将会使用一种称为升级握手的机制。因此，使用WebSocket的应用程序将始终以HTTP/S作为开始，然后再执行升级。这个升级动作发生的确切时刻特定于应用程序；它可能会发生在启动时，也可能会发生在请求了某个特定的URL之后
约定：
如果被请求的 URL 以/ws 结尾，那么我们将会把该协议升级为 WebSocket；
否则，服务器将使用基本的 HTTP/S
服务器逻辑:
图2.png
处理http请求以及websocket
图3.png
//扩展 SimpleChannel-InboundHandler 以处理FullHttpRequest 消息
public class HttpRequestHandler extends SimpleChannelInboundHandler {
private final String wsUri;
private static final File INDEX;
static {
URL location = HttpRequestHandler.class.getProtectionDomain().getCodeSource().getLocation();
try {
String path = location.toURI() + "index.html";
path = !path.contains("file:") ? path : path.substring(5);
INDEX = new File(path);
} catch (URISyntaxException e) {
throw new IllegalStateException("Unable to locate WebsocketChatClient.html", e);
}
}
public HttpRequestHandler(String wsUri) {
this.wsUri = wsUri;
}
@Override
public void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
if (wsUri.equalsIgnoreCase(request.uri())) {//如果请求了 WebSocket协议升级，则增加引用 计数（调用retain()方法），并将它传递给下一个ChannelInboundHandler
ctx.fireChannelRead(request.retain()); //
} else {
if (HttpUtil.is100ContinueExpected(request)) {//处理 100 Continue请求以符合 HTTP 1.1 规范
send100Continue(ctx); //
}
RandomAccessFile file = new RandomAccessFile(INDEX, "r");//
HttpResponse response = new DefaultHttpResponse(request.protocolVersion(), HttpResponseStatus.OK);
response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/html; charset=UTF-8");
boolean keepAlive = HttpUtil.isKeepAlive(request);
if (keepAlive) { //如果请求了keep-alive，则添加所需要的HTTP 头信息
response.headers().set(HttpHeaderNames.CONTENT_LENGTH, file.length());
response.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
}
ctx.write(response); //将 HttpResponse写到客户端
if (ctx.pipeline().get(SslHandler.class) == null) { //将 index.html写到客户端
ctx.write(new DefaultFileRegion(file.getChannel(), 0, file.length()));
} else {
ctx.write(new ChunkedNioFile(file.getChannel()));
}
ChannelFuture future = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);//写LastHttpContent并冲刷至客户端
if (!keepAlive) {//如果没有请求keep-alive，则在写操作完成后关闭 Channel
future.addListener(ChannelFutureListener.CLOSE); //
}
file.close();
}
}
private static void send100Continue(ChannelHandlerContext ctx) {
FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.CONTINUE);
ctx.writeAndFlush(response);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
Channel incoming = ctx.channel();
System.out.println("Client:" + incoming.remoteAddress() + "异常");
// 当出现异常就关闭连接
cause.printStackTrace();
ctx.close();
}
}
public class TextWebSocketFrameHandler extends SimpleChannelInboundHandler {
public static ChannelGroup channels = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
@Override
protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception { //
Channel incoming = ctx.channel();
for (Channel channel : channels) {
if (channel != incoming) {
channel.writeAndFlush(new TextWebSocketFrame("[" + incoming.remoteAddress() + "]" + msg.text()));
} else {
channel.writeAndFlush(new TextWebSocketFrame("[you]" + msg.text()));
}
}
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception { //
Channel incoming = ctx.channel();
// 广播
channels.writeAndFlush(new TextWebSocketFrame("[SERVER] - " + incoming.remoteAddress() + " 加入"));
channels.add(incoming);
System.out.println("Client:" + incoming.remoteAddress() + "加入");
}
@Override
public void handlerRemoved(ChannelHandlerContext ctx) throws Exception { //
Channel incoming = ctx.channel();
// 广播
channels.writeAndFlush(new TextWebSocketFrame("[SERVER] - " + incoming.remoteAddress() + " 离开"));
System.out.println("Client:" + incoming.remoteAddress() + "离开");
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception { //
Channel incoming = ctx.channel();
System.out.println("Client:" + incoming.remoteAddress() + "在线");
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception { //
Channel incoming = ctx.channel();
System.out.println("Client:" + incoming.remoteAddress() + "掉线");
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) //
throws Exception {
Channel incoming = ctx.channel();
System.out.println("Client:" + incoming.remoteAddress() + "异常");
// 当出现异常就关闭连接
cause.printStackTrace();
ctx.close();
}
}
public class WebSocketChatServerInitializer extends ChannelInitializer {
@Override
public void initChannel(SocketChannel ch) throws Exception {//（2）
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new HttpServerCodec());
pipeline.addLast(new HttpObjectAggregator(64*1024));
pipeline.addLast(new ChunkedWriteHandler());
pipeline.addLast(new HttpRequestHandler("/ws"));
pipeline.addLast(new WebSocketServerProtocolHandler("/ws"));
pipeline.addLast(new TextWebSocketFrameHandler());
}
}
Netty文档
ChannelGroup
线程安全的Set，包含开放的Channel，并在其上提供各种批量操作。 使用ChannelGroup，您可以将Channels划分为有意义的组（例如，基于每个服务或每个状态）。一个封闭的Channels会自动从集合中删除，因此您不必担心它的生命周期。 添加频道。 一个Channel可以属于多个ChannelGroup。
将消息广播到多个频道
如果需要将消息广播到多个频道，则可以添加与收件人关联的频道并调用write（Object）：
ChannelGroup recipients =
new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
recipients.add(channelA);
recipients.add(channelB);
..
recipients.write(Unpooled.copiedBuffer(
"Service will shut down for maintenance in 5 minutes.",
CharsetUtil.UTF_8));
使用ChannelGroup简化关机过程
如果ServerChannels和非ServerChannels都存在于同一ChannelGroup中，则首先对ServerChannels执行此组上所有请求的I / O操作，然后对其他Channels执行。
一次关闭服务器时，此规则非常有用：
ChannelGroup allChannels =
new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
public static void main(String[] args) throws Exception {
ServerBootstrap b = new ServerBootstrap(..);
...
b.childHandler(new MyHandler());
// Start the server
b.getPipeline().addLast("handler", new MyHandler());
Channel serverChannel = b.bind(..).sync();
allChannels.add(serverChannel);
... Wait until the shutdown signal reception ...
// Close the serverChannel and then all accepted connections.
allChannels.close().awaitUninterruptibly();
}
public class MyHandler extends ChannelInboundHandlerAdapter {
@Override
public void channelActive(ChannelHandlerContext ctx) {
// closed on shutdown.
allChannels.add(ctx.channel());
super.channelActive(ctx);
}
}
参考
<< Netty实战 >>