Netty基础—Netty实现消息推送服务
1.Netty实现HTTP服务器
(1)HTTP请求消息和响应消息
HTTP请求消息由三部分组成：请求行、请求头、请求体。HTTP响应消息也由三部分组成：响应行、响应头、响应体。
(2)Netty实现的HTTP协议栈的优势
Netty实现的HTTP协议栈无论在性能还是在可靠性上，都表现优异，非常适合在非Web容器下的场景使用。相比于传统的Tomcat、Jetty等Web容器，它更加轻量和小巧，灵活性和定制性也更好。
(3)Netty实现的HTTP服务器
public class NettyHttpServer {
private static final Logger logger = LogManager.getLogger(NettyHttpServer.class);
private static final int DEFAULT_PORT = 8998;
private int port;
public NettyHttpServer(int port) {
this.port = port;
}
public void start() throws Exception {
logger.info("Netty Http Server is starting.");
EventLoopGroup bossEventLoopGroup = new NioEventLoopGroup();
EventLoopGroup workerEventLoopGroup = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossEventLoopGroup, workerEventLoopGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline()
//数据进来是自上而下，数据回去时自下而上
.addLast("http-decoder", new HttpRequestDecoder())
.addLast("http-aggregator", new HttpObjectAggregator(65536))
.addLast("http-encoder", new HttpResponseEncoder())
.addLast("http-chunked", new ChunkedWriteHandler())
.addLast("netty-http-server-handler", new NettyHttpServerHandler());
}
});
ChannelFuture channelFuture = serverBootstrap.bind(port).sync();
logger.info("Netty Http Server is started, listened[" + port + "].");
channelFuture.channel().closeFuture().sync();
} finally {
bossEventLoopGroup.shutdownGracefully();
workerEventLoopGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
NettyHttpServer nettyHttpServer = new NettyHttpServer(DEFAULT_PORT);
nettyHttpServer.start();
}
}
public class NettyHttpServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
private static final Logger logger = LogManager.getLogger(NettyHttpServerHandler.class);
protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
logger.info(request);
}
}启动NettyHttpServer，然后在浏览器进行访问，就可以看到输出如下：
Netty Http Server is starting.
Netty Http Server is started, listened[8998].
HttpObjectAggregator$AggregatedFullHttpRequest(decodeResult: success, version: HTTP/1.1, content: CompositeByteBuf(ridx: 0, widx: 0, cap: 0, components=0))
GET / HTTP/1.1
Host: localhost:8998
Connection: keep-alive
sec-ch-ua: ".Not/A)Brand";v="99", "Google Chrome";v="103", "Chromium";v="103"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "macOS"
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: none
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Accept-Encoding: gzip, deflate, br
Accept-Language: zh-CN,zh;q=0.9,en;q=0.8,id;q=0.7,ar;q=0.6
Cookie: _ga=GA1.1.629604539.1641093986
content-length: 0(4)请求的解析处理和响应的编码处理
HTTP服务器最关键的就是请求的解析处理和响应的编码处理，比如会向ChannelPipeline中先后添加不同的解码器和编码器。
首先添加HTTP请求消息解码器HttpRequestDecoder，因为浏览器会把按照HTTP协议组织起来的请求数据序列化成字节数组发送给服务器，而HttpRequestDecoder可以按照HTTP协议从接收到的字节数组中读取出一个完整的请求数据。
然后添加HttpObjectAggregator解码器，它的作用是将多个消息转换为单一的FullHttpRequest或者FullHttpResponse。
接着添加HTTP响应消息编码器HttpResponseEncoder，它的作用是对HTTP响应消息进行编码。
以及添加ChunkedWriteHandler处理器，用来支持异步发送大的码流时也不会占用过多的内存，防止内存溢出。
最后添加NettyHttpServerHandler处理器，用于处理HTTP服务器的响应输出。
public class NettyHttpServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
private static final Logger logger = LogManager.getLogger(NettyHttpServerHandler.class);
protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
String method = request.getMethod().name();
String uri = request.getUri();
logger.info("Receives Http Request: " + method + " " + uri + ".");
String html = "<html><body>Hello, I am Netty Http Server.</body></html>";
ByteBuf byteBuf = Unpooled.copiedBuffer(html, CharsetUtil.UTF_8);
FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
response.headers().set("content-type", "text/html;charset=UTF-8");
response.content().writeBytes(byteBuf);
byteBuf.release();
ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
}
}2.Netty实现WebSocket
(1)HTTP协议的弊端
一.HTTP协议为半双工通信
半双工通信指数据可以在客户端和服务端两个方向传输，但是不能同时传输。它意味着同一时刻，只能有一个方向上的数据在进行传输。
二.HTTP消息冗长而繁琐
HTTP消息包含消息头、消息体、换行符等，通常情况下采用文本方式传输。相比于其他的二进制通信协议，冗长而繁琐。
(2)消息推送之Ajax短轮询
Ajax短轮询是基于HTTP短连接的。具体就是用一个定时器由浏览器对服务器发出HTTP请求，由服务器返回数据给客户端浏览器。
Ajax短轮询的代码实现简单。但由于HTTP请求的Header非常冗长，里面可用数据的比例非常低，所以比较占用带宽和服务器资源，且数据同步不及时。
(3)消息推送之WebSocket
WebSocket本质是一个TCP连接，采用的是全双工通信。
WebSocket中，浏览器和服务器只需要做一个握手动作，两者之间就会形成一条快速通道进行直接数据传输。由于WebSocket基于TCP双向全双工进行消息传递，所以在同一时刻既可以发送消息，也可以接收消息，比HTTP半双工性能好。
WebSocket通过ping/pong帧来保持链路激活，实时性很高，但是浏览器支持度低、代码实现复杂。
(4)WebSocket连接的建立
建立WebSocket连接时，需要通过客户端或者浏览器发出握手请求，这个握手请求是一个HTTP请求。该HTTP请求包含了附加头信息"Upgrade:WebSocket"，表明这是一个申请协议升级的HTTP请求。
服务端解析这些附加的头信息，然后生成应答信息返回给客户端。这样客户端和服务端的WebSocket连接就建立起来了，双方可以通过这个连接通道自由地传递信息，并且这个连接会持续存在直到一方主动关闭连接。
(5)基于WebSocket协议开发NettyServer
可以基于TCP协议用Netty来开发客户端和服务端进行相互通信，但粘包半包问题需要手动进行处理。
可以基于HTTP协议用Netty来开发一个HTTP服务器，服务器接收浏览器发送过来的HTTP请求后，返回HTTP响应回浏览器。
也可以基于WebSocket协议来开发一个Netty服务器，此时前端HTML代码会基于socket协议和Netty服务器建立长连接。这样Netty服务器就可以和浏览器里运行的HTML通过WebSocket协议建立长连接，从而使得Netty服务器可以主动推送数据给浏览器里的HTML页面。
WebSocket协议底层也是基于TCP协议来实现的，只不过是在TCP协议的基础上封装了一层更高层次的WebSocket协议。
public class NettyWebSocketServer {
private static final Logger logger = LogManager.getLogger(NettyWebSocketServer.class);
private static final int DEFAULT_PORT = 8998;
private int port;
public NettyWebSocketServer(int port) {
this.port = port;
}
public void start() throws Exception {
logger.info("Netty WebSocket Server is starting.");
EventLoopGroup bossEventLoopGroup = new NioEventLoopGroup();
EventLoopGroup workerEventLoopGroup = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossEventLoopGroup, workerEventLoopGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline()
.addLast(new HttpServerCodec())
.addLast(new ChunkedWriteHandler())
.addLast(new HttpObjectAggregator(1024 * 32))
.addLast(new WebSocketServerProtocolHandler("/websocket"))
.addLast("netty-web-socket-server-handler", new NettyWebSocketServerHandler());
}
});
ChannelFuture channelFuture = serverBootstrap.bind(port).sync();
logger.info("Netty WebSocket Server server is started, listened[" + port + "].");
channelFuture.channel().closeFuture().sync();
} finally {
bossEventLoopGroup.shutdownGracefully();
workerEventLoopGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
NettyWebSocketServer nettyHttpServer = new NettyWebSocketServer(DEFAULT_PORT);
nettyHttpServer.start();
}
}(6)WebSocketServer的请求数据处理逻辑开发
public class NettyWebSocketServerHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
private static final Logger logger = LogManager.getLogger(NettyWebSocketServerHandler.class);
private static ChannelGroup webSocketClients = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
//WebSocket网页代码里发送过来的数据
String request = msg.text();
logger.info("Netty Server receives request: " + request + ".");
TextWebSocketFrame response = new TextWebSocketFrame("Hello, I am Netty Server.");
ctx.writeAndFlush(response);
}
//如果一个网页WebSocket客户端跟Netty Server建立了连接之后，会触发这个方法
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
webSocketClients.add(ctx.channel());
}
@Override
public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
logger.info("websocket client is closed, channel id: " + ctx.channel().id().asLongText() + "[" + ctx.channel().id().asShortText() + "]");
}
}(7)WebSocketServer的HTTP与chunk处理分析
浏览器里面运行的是HTML网页代码，WebSocket就是在HTML网页代码里嵌入WebSocket代码，可以让浏览器里的HTML网页代码跟NettyServer建立连接，并且是基于长连接发送数据。
浏览器会按照WebSocket协议(底层基于HTTP协议)组织请求数据格式，然后把数据序列化成字节数组，接着通过网络连接把字节数组传输发送给NettyServer，NettyServer会通过数据处理链条来进行处理接收到的字节数组数据。
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline()
//浏览器的字节数组数据进来以后，字节数组数据先用http协议来处理，把字节数组转换为一个HttpRequest请求对象
//最后数据返回给浏览器前，又会对HttpResponse对象进行编码成字节数组
.addLast(new HttpServerCodec())
//chunked write用于大量数据流时的分chunk块，也就是数据实在是太大了就必须得分chunk
//大量数据流进来时，可以分chunk块来读；大量数据流出去时，可以分chunk块来写；
.addLast(new ChunkedWriteHandler())
//如果想要让很多http不要拆分成很多段过来，可以把完整的请求数据聚合到一起再给过来
.addLast(new HttpObjectAggregator(1024 * 32))
//基于前面已经转换好的请求数据对象，会在这里基于WebSocket协议再次做一个处理
//由于传输时是基于http协议传输过来的，而封装的内容是按webSocket协议来封装的http请求数据
//所以必须在这里提取http请求里面的数据，然后按照WebSocket协议来进行解析处理，把数据提取出来作为WebSocket的数据片段
.addLast(new WebSocketServerProtocolHandler("/websocket"))
//响应数据输出时，顺序是反的，第一步原始数据必须先经过WebSocket协议转换
//WebSocket协议数据，必须经过HTTP协议处理，但最终会encode编码成一个HTTP协议的响应数据
//然后服务端将HTTP响应数据序列化的字节数组，传输给浏览器
//浏览器拿到字节数组后进行反序列化，拿到一个HTTP协议响应数据，提取出内容再按照WebSocket协议来处理
//最终把普通的数据给WebSocket代码
.addLast("netty-web-socket-server-handler", new NettyWebSocketServerHandler());
}(8)WebSocket网页客户端代码开发与实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>websocket网页</title>
</head>
<body onload="connectServer();">
<script type="text/javascript">
var websocket;
function connectServer() {
if ("WebSocket" in window) {
console.log("Your browser supports websocket!");
websocket = new WebSocket("ws://localhost:8998/websocket");
websocket.onopen = function() {
console.log("Send request to netty server.");
websocket.send("I am websocket client.");
}
websocket.onmessage = function(ev) {
var response = ev.data;
console.log("Receive response from netty server: " + response);
}
}
}
</script>
</body>
</html>启动Netty Server，然后打开该HTML即可看到console的输出。
WebSocket和Netty Server配合起来开发说明：
如果Server端要主动推送一些通知(push)给网页端正在浏览网页的用户，如推送用户可能感兴趣的商品、关注的新闻。那么在用户进入网页后可以询问用户，是否愿意收到服务端发送的xx提示和通知。如果用户愿意，那么网页里的WebSocket完全可以跟NettyServer构建一个长连接。这样NettyServer在必要时，就可以反向推送通知(push)给用户，浏览器里的网页可能会弹出一个push通知用户xx讯息。
3.Netty实现的消息推送系统
(1)基于WebSocket的消息推送系统说明
首先需要一个运营系统能够基于NettyClient和PushServer建立WebSocket长连接，然后浏览器客户端也要和PushServer建立好WebSocket长连接，接着运营系统会让NettyClient发送Push推送消息给PushServer，最后PushServer再把推送消息发送给浏览器客户端。
首先启动PushServer，然后打开多个网页客户端查看console，接着启动运营客系统在控制台输入消息，这样就可以完成一个完整的消息推送的交互了。
(2)消息推送系统的PushServer
public class NettyPushServer {
private static final Logger logger = LogManager.getLogger(NettyPushServer.class);
private static final int DEFAULT_PORT = 8998;
private int port;
public NettyPushServer(int port) {
this.port = port;
}
public void start() throws Exception {
logger.info("Netty Push Server is starting.");
EventLoopGroup bossEventLoopGroup = new NioEventLoopGroup();
EventLoopGroup workerEventLoopGroup = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossEventLoopGroup, workerEventLoopGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline()
.addLast("logging", new LoggingHandler("DEBUG"))
.addLast("http-codec", new HttpServerCodec())
.addLast("aggregator", new HttpObjectAggregator(65536))
.addLast("http-chunked", new ChunkedWriteHandler())
.addLast("netty-push-server-handler", new NettyPushServerHandler());
}
});
ChannelFuture channelFuture = serverBootstrap.bind(port).sync();
logger.info("Netty Push Server is started, listened[" + port + "].");
channelFuture.channel().closeFuture().sync();
} finally {
bossEventLoopGroup.shutdownGracefully();
workerEventLoopGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
NettyPushServer nettyHttpServer = new NettyPushServer(DEFAULT_PORT);
nettyHttpServer.start();
}
}
public class NettyPushServerHandler extends SimpleChannelInboundHandler<Object> {
private static final Logger logger = LogManager.getLogger(NettyPushServerHandler.class);
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
logger.info("Client Connection Established: " + ctx.channel());
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
logger.info("Client Disconnected: " + ctx.channel());
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
if (msg instanceof FullHttpRequest) {
handleHttpRequest(ctx, (FullHttpRequest) msg);
} else if(msg instanceof WebSocketFrame) {
handleWebSocketFrame(ctx, (WebSocketFrame) msg);
}
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame webSocketFrame) {
}
private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest request) {
}
}(3)消息推送系统的连接管理封装
//用来管理连接
public class ChannelManager {
private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
private static ConcurrentHashMap<String, ChannelId> channelIds = new ConcurrentHashMap<String, ChannelId>();
public static void add(Channel channel) {
channelGroup.add(channel);
channelIds.put(channel.id().asShortText(), channel.id());
}
public static void remove(Channel channel) {
channelGroup.remove(channel);
channelIds.remove(channel.id().asShortText());
}
public static Channel get(String id) {
return channelGroup.find(channelIds.get(id));
}
public static void pushToAllChannels(TextWebSocketFrame webSocketFrame) {
channelGroup.writeAndFlush(webSocketFrame);
}
}
public class NettyPushServerHandler extends SimpleChannelInboundHandler<Object> {
...
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
logger.info("Client Connection Established: " + ctx.channel());
ChannelManager.add(ctx.channel());
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
logger.info("Client Disconnected: " + ctx.channel());
ChannelManager.remove(ctx.channel());
}
...
}(4)消息推送系统的ping-pong探测
public class NettyPushServerHandler extends SimpleChannelInboundHandler<Object> {
...
private WebSocketServerHandshaker webSocketServerHandshaker;
...
protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
if (msg instanceof FullHttpRequest) {
handleHttpRequest(ctx, (FullHttpRequest) msg);
} else if(msg instanceof WebSocketFrame) {
handleWebSocketFrame(ctx, (WebSocketFrame) msg);
}
}
private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame webSocketFrame) {
//WebSocket网页客户端发送的是ping消息，它会不停的ping服务端，看看长连接是否存活和有效
if (webSocketFrame instanceof PingWebSocketFrame) {
logger.info("Receive ping frame from client: " + ctx.channel());
WebSocketFrame pongWebSocketFrame = new PongWebSocketFrame(webSocketFrame.content().retain());
ctx.channel().write(pongWebSocketFrame);
return;
}
//WebSocket网页客户端发送一个请求过来，请求关闭这个WebSocket连接
if (webSocketFrame instanceof CloseWebSocketFrame) {
logger.info("Receive close WebSocket request from client: " + ctx.channel());
webSocketServerHandshaker.close(ctx.channel(), ((CloseWebSocketFrame) webSocketFrame).retain());
return;
}
...
}
...
}(5)消息推送系统的全连接推送
public class NettyPushServerHandler extends SimpleChannelInboundHandler<Object> {
...
protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
if (msg instanceof FullHttpRequest) {
handleHttpRequest(ctx, (FullHttpRequest) msg);
} else if(msg instanceof WebSocketFrame) {
handleWebSocketFrame(ctx, (WebSocketFrame) msg);
}
}
private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame webSocketFrame) {
//WebSocket网页客户端发送的是ping消息，它会不停的ping服务端，看看长连接是否存活和有效
if (webSocketFrame instanceof PingWebSocketFrame) {
logger.info("Receive ping frame from client: " + ctx.channel());
WebSocketFrame pongWebSocketFrame = new PongWebSocketFrame(webSocketFrame.content().retain());
ctx.channel().write(pongWebSocketFrame);
return;
}
//WebSocket网页客户端发送一个请求过来，请求关闭这个WebSocket连接
if (webSocketFrame instanceof CloseWebSocketFrame) {
logger.info("Receive close WebSocket request from client: " + ctx.channel());
webSocketServerHandshaker.close(ctx.channel(), ((CloseWebSocketFrame) webSocketFrame).retain());
return;
}
//WebSocket网页客户端发送请求，但它不是text文本请求
if (!(webSocketFrame instanceof TextWebSocketFrame)) {
logger.error("Netty Push Server only support text frame, does not support other type frame.");
String errorMsg = String.format("%s type frame is not supported.", webSocketFrame.getClass().getName());
throw new UnsupportedOperationException(errorMsg);
}
//WebSocket网页客户端发送一个文本请求过来，是TextFrame类型的
String request = ((TextWebSocketFrame)webSocketFrame).text();
logger.info("Receive text frame[" + request + "] from client: " + ctx.channel());
//构建响应
TextWebSocketFrame response = new TextWebSocketFrame(request);
//发送给所有连接，全连接推送
ChannelManager.pushToAllChannels(response);
}
...
}(6)消息推送系统的HTTP响应和握手
public class NettyPushServerHandler extends SimpleChannelInboundHandler<Object> {
...
private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest request) {
if (!request.decoderResult().isSuccess() || (!"websocket".equals(request.headers().get("Upgrade")))) {
DefaultFullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.BAD_REQUEST);
sendHttpResponse(ctx, request, response);
return;
}
logger.info("Receive handshake request from client: " + ctx.channel());
//握手建立
WebSocketServerHandshakerFactory factory = new WebSocketServerHandshakerFactory("ws://localhost:8998/push", null, false);
webSocketServerHandshaker = factory.newHandshaker(request);
if (webSocketServerHandshaker == null) {
WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
} else {
webSocketServerHandshaker.handshake(ctx.channel(), request);
logger.info("Netty push server handshake with client: " + ctx.channel());
}
}
//HTTP响应
private void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest request, DefaultFullHttpResponse response) {
if (response.status().code() != RESPONSE_CODE_OK) {
ByteBuf byteBuf = Unpooled.copiedBuffer(response.status().toString(), CharsetUtil.UTF_8);
response.content().writeBytes(byteBuf);
logger.info("Http Response is not ok: " + byteBuf.toString(CharsetUtil.UTF_8));
byteBuf.release();
}
ChannelFuture channelFuture = ctx.channel().writeAndFlush(response);
if (response.status().code() != RESPONSE_CODE_OK) {
channelFuture.addListener(ChannelFutureListener.CLOSE);
}
}
...
}(7)消息推送系统的运营客户端
public class OperationNettyClient {
private static final Logger logger = LogManager.getLogger(OperationNettyClient.class);
private static final String WEB_SOCKET_SCHEME = "ws";
private static final String WSS_SCHEME = "wss";
private static final String LOCAL_HOST = "127.0.0.1";
private static final String PUSH_SERVER_URI = System.getProperty("url", "ws://127.0.0.1:8998/push");
private static URI uri;
private static String scheme;
private static String host;
private static int port;
private static SslContext sslContext;
private EventLoopGroup eventLoopGroup;
public void start() throws Exception {
//...
}
public static void main(String[] args) throws Exception {
uri = new URI(PUSH_SERVER_URI);
scheme = getScheme(uri);
host = getHost(uri);
port = getPort(uri, scheme);
checkScheme(scheme);
initSslContext(scheme);
}
private static String getScheme(URI pushServerUri) {
return pushServerUri.getScheme() == null ? WEB_SOCKET_SCHEME : pushServerUri.getScheme();
}
private static String getHost(URI pushServerUri) {
return pushServerUri.getHost() == null ? LOCAL_HOST : pushServerUri.getHost();
}
private static int getPort(URI pushServerUri, String scheme) {
int port;
if (pushServerUri.getPort() == -1) {
if (WEB_SOCKET_SCHEME.equals(scheme)) {
port = 80;
} else if(WSS_SCHEME.equals(scheme)) {
port = 443;
} else {
port = -1;
}
} else {
port = pushServerUri.getPort();
}
return port;
}
//检查scheme是否是ws或wss
private static void checkScheme(String scheme) {
if (!WEB_SOCKET_SCHEME.equals(scheme) && !WSS_SCHEME.equals(scheme)) {
logger.error("Only Support ws or wss scheme.");
throw new RuntimeException("Only Support ws or wss scheme.");
}
}
//如果WebSocket使用了SSL，也就是wss，那么初始化对应的sslContext
private static void initSslContext(String scheme) throws Exception {
boolean enableSSL = WSS_SCHEME.equals(scheme);
if (enableSSL) {
sslContext = SslContextBuilder.forClient().trustManager(InsecureTrustManagerFactory.INSTANCE).build();
} else {
sslContext = null;
}
}
}(8)运营客户端连接PushServer
public class OperationNettyClient {
private static final Logger logger = LogManager.getLogger(OperationNettyClient.class);
private static final String WEB_SOCKET_SCHEME = "ws";
private static final String WSS_SCHEME = "wss";
private static final String LOCAL_HOST = "127.0.0.1";
private static final String PUSH_SERVER_URI = System.getProperty("url", "ws://127.0.0.1:8998/push");
private static final String INPUT_MESSAGE_QUIT = "quit";
private static final String INPUT_MESSAGE_CLOSE = "close";
private static final String INPUT_MESSAGE_PING = "ping";
private static URI uri;
private static String scheme;
private static String host;
private static int port;
private static SslContext sslContext;
private EventLoopGroup eventLoopGroup;
public Channel start() throws Exception {
logger.info("Operation Netty Client is connecting.");
eventLoopGroup = new NioEventLoopGroup();
WebSocketClientHandshaker webSocketClientHandshaker = WebSocketClientHandshakerFactory.newHandshaker(uri, WebSocketVersion.V13, null, true, new DefaultHttpHeaders());
final OperationNettyClientHandler operationNettyClientHandler = new OperationNettyClientHandler(webSocketClientHandshaker);
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(eventLoopGroup)
.channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline channelPipeline = ch.pipeline();
if (sslContext != null) {
channelPipeline.addLast(sslContext.newHandler(ch.alloc(), host, port));
}
channelPipeline.addLast(new HttpClientCodec())
.addLast(new HttpObjectAggregator(65536))
.addLast(WebSocketClientCompressionHandler.INSTANCE)
.addLast(operationNettyClientHandler);
}
});
Channel channel = bootstrap.connect(uri.getHost(), port).sync().channel();
logger.info("Operation Netty Client connected to push server.");
operationNettyClientHandler.channelFuture().sync();
return channel;
}
public void shutdownGracefully() {
eventLoopGroup.shutdownGracefully();
}
public static void main(String[] args) throws Exception {
uri = new URI(PUSH_SERVER_URI);
scheme = getScheme(uri);
host = getHost(uri);
port = getPort(uri, scheme);
checkScheme(scheme);
initSslContext(scheme);
OperationNettyClient operationNettyClient = new OperationNettyClient();
try {
Channel channel = operationNettyClient.start();
} finally {
operationNettyClient.shutdownGracefully();
}
}
...
}(9)运营客户端的Handler处理器
public class OperationNettyClientHandler extends SimpleChannelInboundHandler<Object> {
private static final Logger logger = LogManager.getLogger(OperationNettyClientHandler.class);
private WebSocketClientHandshaker webSocketClientHandshaker;
private ChannelFuture channelFuture;
public OperationNettyClientHandler(WebSocketClientHandshaker webSocketClientHandshaker) {
this.webSocketClientHandshaker = webSocketClientHandshaker;
}
public ChannelFuture channelFuture() {
return channelFuture;
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
channelFuture = ctx.newPromise();
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
webSocketClientHandshaker.handshake(ctx.channel());
logger.info("Operation Netty Client send WebSocket handshake request.");
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
logger.info("netty client disconnected.");
}
protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
Channel channel = ctx.channel();
if (!webSocketClientHandshaker.isHandshakeComplete()) {
try {
webSocketClientHandshaker.finishHandshake(channel, (FullHttpResponse) msg);
logger.info("Netty Client connected.");
((ChannelPromise)channelFuture).setSuccess();
} catch(WebSocketHandshakeException e) {
logger.error("WebSocket handshake failed.", e);
((ChannelPromise)channelFuture).setFailure(e);
}
return;
}
if (msg instanceof FullHttpResponse) {
FullHttpResponse response = (FullHttpResponse) msg;
throw new IllegalStateException("Not Supported HTTP Response.");
}
WebSocketFrame webSocketFrame = (WebSocketFrame) msg;
if (webSocketFrame instanceof TextWebSocketFrame) {
TextWebSocketFrame textWebSocketFrame = (TextWebSocketFrame) webSocketFrame;
logger.info("Receives text frame: " + textWebSocketFrame.text());
} else if(webSocketFrame instanceof PongWebSocketFrame) {
logger.info("Receives pong frame: " + webSocketFrame);
} else if(webSocketFrame instanceof CloseWebSocketFrame) {
logger.info("Receives close WebSocket frame, Netty Client is closing.");
channel.close();
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
logger.error("Operation Netty client handler exception caught.", cause);
if (!channelFuture.isDone()) {
((ChannelPromise)channelFuture).setFailure(cause);
}
ctx.close();
}
}(10)运营客户端发送推送消息
public class OperationNettyClient {
...
public void waitInputMessage(Channel channel) throws Exception {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
while(true) {
logger.info("Wait for input message.");
String message = bufferedReader.readLine();
if (INPUT_MESSAGE_QUIT.equals(message)) {
break;
} else if(INPUT_MESSAGE_CLOSE.equals(message)) {
channel.writeAndFlush(new CloseWebSocketFrame());
channel.closeFuture().sync();
break;
} else if(INPUT_MESSAGE_PING.equals(message)) {
WebSocketFrame webSocketFrame = new PingWebSocketFrame(Unpooled.wrappedBuffer(new byte[] {8, 1, 8, 1}));
channel.writeAndFlush(webSocketFrame);
} else {
WebSocketFrame webSocketFrame = new TextWebSocketFrame(message);
channel.writeAndFlush(webSocketFrame);
}
}
}
public static void main(String[] args) throws Exception {
uri = new URI(PUSH_SERVER_URI);
scheme = getScheme(uri);
host = getHost(uri);
port = getPort(uri, scheme);
checkScheme(scheme);
initSslContext(scheme);
OperationNettyClient operationNettyClient = new OperationNettyClient();
try {
Channel channel = operationNettyClient.start();
//运营客户端发送消息入口
operationNettyClient.waitInputMessage(channel);
} finally {
operationNettyClient.shutdownGracefully();
}
}
...
}(11)浏览器客户端接收推送消息
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>websocket网页</title>
</head>
<body onload="connectServer();">
<script type="text/javascript">
var websocket;
function connectServer() {
if ("WebSocket" in window) {
console.log("your browser supports websocket!");
websocket = new WebSocket("ws://localhost:8998/push");
websocket.onopen = function() {
console.log("established connection with push server.");
}
websocket.onmessage = function(ev) {
var response = ev.data;
console.log("receives push message from netty server: " + response);
}
}
}
</script>
</body>
</html>文章转载自：东阳马生架构
原文链接：Netty基础—7.Netty实现消息推送服务 - 东阳马生架构 - 博客园
体验地址：引迈 - JNPF快速开发平台_低代码开发平台_零代码开发平台_流程设计器_表单引擎_工作流引擎_软件架构