由于http协议为应答模式的连接，无法保持长连接于是引入了websocket套接字长连接概念，能够保持数据持久性的交互；本篇文章将告知读者如何使用netty实现简单的消息推送功能
websocket请求头
GET / HTTP/1.1
Host: 127.0.0.1:8096
Connection: Upgrade
Pragma: no-cache
Cache-Control: no-cache
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.82 Safari/537.36
Upgrade: websocket
Origin: http://localhost:8056
Sec-WebSocket-Version: 13
websocket请求头 会有 Connection 升级为 Upgrade, 并且Upgrade 属性值为 websocket
引入依赖
引入netty和 引擎模板依赖
<dependencies>
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.55.Final</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
</dependencies>
创建Nio线程组，并在辅助启动器中中注入 自定义处理器；定义套接字端口为8096；
/**
* @author lsc
* <p> </p>
*/
@Slf4j
public class WebSocketServer {
public void init(){
NioEventLoopGroup boss=new NioEventLoopGroup();
NioEventLoopGroup work=new NioEventLoopGroup();
try {
ServerBootstrap bootstrap=new ServerBootstrap();
bootstrap.group(boss,work);
bootstrap.channel(NioServerSocketChannel.class);
// 自定义处理器
bootstrap.childHandler(new SocketChannelInitializer());
Channel channel = bootstrap.bind(8096).sync().channel();
log.info("------------webSocket服务器启动成功-----------："+channel);
channel.closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
log.info("---------运行出错----------："+e);
}finally {
boss.shutdownGracefully();
work.shutdownGracefully();
log.info("------------websocket服务器已关闭----------------");
}
}
}
SocketChannelInitializer 中定义了聚合器 HttpObjectAggregator 将多个http片段消息聚合成完整的http消息，并且指定大小为65536；最后注入自定义的WebSocketHandler；
/**
* @author lsc
* <p> </p>
*/
public class SocketChannelInitializer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) {
//设置log监听器
ch.pipeline().addLast("logging",new LoggingHandler("DEBUG"));
//设置解码器
ch.pipeline().addLast("http-codec",new HttpServerCodec());
//聚合器
ch.pipeline().addLast("aggregator",new HttpObjectAggregator(65536));
//用于大数据的分区传输
ch.pipeline().addLast("http-chunked",new ChunkedWriteHandler());
//自定义业务handler
ch.pipeline().addLast("handler",new WebSocketHandler());
}
}
WebSocketHandler 中对接收的消息进行判定，如果是websocket 消息 则将消息广播给所有通道；
/**
* @author lsc
* <p> </p>
*/
@Slf4j
public class WebSocketHandler extends SimpleChannelInboundHandler<Object> {
// 存放已经连接的通道
private static ConcurrentMap<String, Channel> ChannelMap=new ConcurrentHashMap();
@Override
protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
if (msg instanceof FullHttpRequest){
System.out.println("------------收到http消息--------------"+msg);
handleHttpRequest(ctx,(FullHttpRequest)msg);
}else if (msg instanceof WebSocketFrame){
//处理websocket客户端的消息
String message = ((TextWebSocketFrame) msg).text();
System.out.println("------------收到消息--------------"+message);
// ctx.channel().writeAndFlush(new TextWebSocketFrame(message));
// 将消息回复给所有连接
Collection<Channel> values = ChannelMap.values();
for (Channel channel: values){
channel.writeAndFlush(new TextWebSocketFrame(message));
}
}
}
/**
* @author lsc
* <p> 处理http请求升级</p>
*/
private void handleHttpRequest(ChannelHandlerContext ctx,
FullHttpRequest req) throws Exception {
// 该请求是不是websocket upgrade请求
if (isWebSocketUpgrade(req)) {
String ws = "ws://127.0.0.1:8096";
WebSocketServerHandshakerFactory factory = new WebSocketServerHandshakerFactory(ws, null, false);
WebSocketServerHandshaker handshaker = factory.newHandshaker(req);
if (handshaker == null) {// 请求头不合法, 导致handshaker没创建成功
WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
} else {
// 响应该请求
handshaker.handshake(ctx.channel(), req);
}
return;
}
}
//n1.GET? 2.Upgrade头 包含websocket字符串?
private boolean isWebSocketUpgrade(FullHttpRequest req) {
HttpHeaders headers = req.headers();
return req.method().equals(HttpMethod.GET)
&& headers.get(HttpHeaderNames.UPGRADE).equals("websocket");
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
//添加连接
log.debug("客户端加入连接："+ctx.channel());
Channel channel = ctx.channel();
ChannelMap.put(channel.id().asShortText(),channel);
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
//断开连接
log.debug("客户端断开连接："+ctx.channel());
Channel channel = ctx.channel();
ChannelMap.remove(channel.id().asShortText());
}
}
最后将WebSocketServer 注入spring监听器，在服务启动的时候运行；
@Slf4j
@Component
public class ApplicationConfig implements ApplicationListener<ApplicationReadyEvent> {
@Override
public void onApplicationEvent(ApplicationReadyEvent applicationReadyEvent) {
WebSocketServer webSocketServer = new WebSocketServer();
webSocketServer.init();
}
}
编写 IndexController 对视图进行转发
/**
* @author lsc
* <p> </p>
*/
@Controller
public class IndexController {
@GetMapping("index")
public ModelAndView index(){
ModelAndView modelAndView = new ModelAndView("socket");
return modelAndView;
}
}
html
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>用户页面</title>
</head>
<body>
<div id="msg"></div>
<input type="text" id="text">
<input type="submit" value="send" onclick="send()">
</body>
<script>
var msg = document.getElementById("msg");
var wsServer = 'ws://127.0.0.1:8096';
var websocket = new WebSocket(wsServer);
//监听连接打开
websocket.onopen = function (evt) {
msg.innerHTML = "The connection is open";
};
//监听服务器数据推送
websocket.onmessage = function (evt) {
msg.innerHTML += "<br>" + evt.data;
};
//监听连接关闭
websocket.onclose = function (evt) {
alert("连接关闭");
};
function send() {
var text = document.getElementById("text").value
websocket.send(text);
}
</script>
</html>
附上配置文件
server:
port: 8056
spring:
# 引擎模板配置
thymeleaf:
cache: false # 关闭缓存
mode: html # 去除htm5严格校验
prefix: classpath:/templates/ # 指定 thymeleaf 模板路径
encoding: UTF-8 # 指定字符集编码
suffix: .html
运行服务后
前端页面显示消息
服务端打印消息
源码获取：知识追寻者公众号回复：netty
配套教程