Netty 搭建 WebSocket 服务端
一、编码器、解码器
... ...
@Autowired
private HttpRequestHandler httpRequestHandler;
@Autowired
private TextWebSocketFrameHandler textWebSocketFrameHandler;
... ...
.childHandler(new ChannelInitializer<SocketChannel> () {
@Override
protected void initChannel(SocketChannel channel) throws Exception {
// WebSocket 是基于 Http 协议的，要使用 Http 解编码器
channel.pipeline().addLast("http-codec", new HttpServerCodec());
// 用于大数据流的分区传输
channel.pipeline().addLast("http-chunked",new ChunkedWriteHandler());
// 将多个消息转换为单一的 request 或者 response 对象，最终得到的是 FullHttpRequest 对象
channel.pipeline().addLast("aggregator", new HttpObjectAggregator(65536));
// 创建 WebSocket 之前会有唯一一次 Http 请求 (Header 中包含 Upgrade 并且值为 websocket)
channel.pipeline().addLast("http-request",httpRequestHandler);
// 处理所有委托管理的 WebSocket 帧类型以及握手本身
// 入参是 ws://server:port/context_path 中的 contex_path
channel.pipeline().addLast("websocket-server", new WebSocketServerProtocolHandler(socketUri));
// WebSocket RFC 定义了 6 种帧，TextWebSocketFrame 是我们唯一真正需要处理的帧类型
channel.pipeline().addLast("text-frame",textWebSocketFrameHandler);
}
});
... ...
其中 HttpRequestHandler 和 TextWebSocketFrameHandler 是自定义 Handler
1.1 HttpRequestHandler
@Component
@ChannelHandler.Sharable
public class HttpRequestHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
private static final Logger LOGGER = LoggerFactory.getLogger(HttpRequestHandler.class);
@Value("${server.socket-uri}")
private String socketUri;
@Override
protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest msg) throws Exception {
if (msg.uri().startsWith(socketUri)) {
String userId = UriUtil.getParam(msg.uri(), "userId");
if (userId != null) {
// todo: 用户校验，重复登录判断
ChannelSupervise.addChannel(userId, ctx.channel());
ctx.fireChannelRead(msg.setUri(socketUri).retain());
} else {
ctx.close();
}
} else {
ctx.close();
}
}
}
1.2 TextWebSocketFrameHandler
@Component
@ChannelHandler.Sharable
public class TextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
private static final Logger LOGGER = LoggerFactory.getLogger(TextWebSocketFrameHandler.class);
@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
if (evt instanceof WebSocketServerProtocolHandler.HandshakeComplete) {
ctx.pipeline().remove(HttpRequestHandler.class);
}
super.userEventTriggered(ctx, evt);
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
String requestMsg = msg.text();
String responseMsg = "服务端接收客户端消息：" + requestMsg;
TextWebSocketFrame resp = new TextWebSocketFrame(responseMsg);
ctx.writeAndFlush(resp.retain());
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
LOGGER.error(ctx.channel().id().asShortText(), cause);
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception { // (6)
ChannelSupervise.removeChannel(ctx.channel());
LOGGER.info("[%s]断开连接", ctx.channel().id().asShortText());
}
}
二、主动向客户端推送消息
2.1 推送工具类
public class ChannelSupervise {
private static ChannelGroup GlobalGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
private static ConcurrentMap<String, ChannelId> UserChannelMap = new ConcurrentHashMap();
private static ConcurrentMap<String, String> ChannelUserMap = new ConcurrentHashMap();
public static void addChannel(String userId, Channel channel){
GlobalGroup.add(channel);
UserChannelMap.put(userId, channel.id());
ChannelUserMap.put(channel.id().asShortText(), userId);
}
public static void removeChannel(Channel channel){
GlobalGroup.remove(channel);
String userId = ChannelUserMap.get(channel.id().asShortText());
UserChannelMap.remove(userId);
ChannelUserMap.remove(channel.id().asShortText());
}
public static void sendToUser(String userId, String msg){
TextWebSocketFrame textWebSocketFrame = new TextWebSocketFrame(msg);
Channel channel = GlobalGroup.find(UserChannelMap.get(userId));
channel.writeAndFlush(textWebSocketFrame);
}
public static void sendToAll(String msg){
TextWebSocketFrame textWebSocketFrame = new TextWebSocketFrame(msg);
GlobalGroup.writeAndFlush(textWebSocketFrame);
}
}
支持向具体某个客户端发送消息，或者群发消息
2.2 推送接口
@RestController
public class WebsocketController {
@RequestMapping("sendToAll")
public void sendToAll(String msg) {
ChannelSupervise.sendToAll(msg);
}
@RequestMapping("sendToUser")
public void sendToUser(String userId, String msg) {
ChannelSupervise.sendToUser(userId, msg);
}
}
三、测试
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>WebSocket客户端</title>
</head>
<body>
<script type="text/javascript">
var socket;
function connect(){
var userId = document.getElementById('userId').value;
if(window.WebSocket){
// 参数就是与服务器连接的地址
// socket = new WebSocket('ws://localhost:8081/ws');
socket = new WebSocket('ws://localhost:8081/ws?userId=' + userId);
// 客户端收到服务器消息的时候就会执行这个回调方法
socket.onmessage = function (event) {
var response = document.getElementById('response');
response.innerHTML = response.innerHTML
+ '<p style="color:LimeGreen;"> 接收：' + event.data + '</p>';
}
// 连接建立的回调函数
socket.onopen = function(event){
var status = document.getElementById('status');
status.innerHTML = '<p style="color:YellowGreen;">WebSocket 连接开启</p>';
}
// 连接断掉的回调函数
socket.onclose = function (event) {
var status = document.getElementById('status');
status.innerHTML = '<p style="color:Red;">WebSocket 连接关闭</p>';
}
}else{
var status = document.getElementById('status');
status.innerHTML = '<p style="color:Red;">浏览器不支持 WebSocket</p>';
}
}
// 发送数据
function send(message){
if(!window.WebSocket){
return;
}
var ta = document.getElementById('response');
ta.innerHTML = ta.innerHTML + '<p style="color:SkyBlue;"> 发送：' + message + '</p>';
// 当websocket状态打开
if(socket.readyState == WebSocket.OPEN){
socket.send(message);
}else{
var response = document.getElementById("response");
response.innerHTML = '<p style="color:Red;">连接没有开启</p>';
}
}
</script>
<form onsubmit="return false">
<label for="userId">用户ID:</label>
<input type="text" name="userId" id="userId" />
<input type ="button" value="连接服务器" onclick="connect();">
</form>
<div id ="status"></div>
<form onsubmit="return false">
<input name = "message" style="width: 200px;"></input>
<input type ="button" value="发送消息" onclick="send(this.form.message.value);">
</form>
<div id ="response"></div>
<input type="button" onclick="javascript:document.getElementById('response').innerHTML=''" value="清空消息">
</body>
</html>
注意
因为自定义 Handler 使用依赖注入实例化，所以需要添加 @ChannelHandler.Sharable 注解，否则会报错：is not a @Sharable handler, so can’t be added or removed multiple times.
参考
完整代码：GitHub
