netty websockt之断连重试

断连重试有以下两点考虑：

1、连接异常，比如网络抖动导致连接失败；

2、连接过程中断开连接重试；

主要用到两个工具类：

ChannelFutureListener监听ChannelFuture..isSuccess()；

ChannelInboundHandlerAdapter重写channelInactive，当连接变为不活跃，则回调该方法。

完整代码如下：

@Component
public class WebSocketClient {

    private Channel channel;

    private Bootstrap bootstrap;

    private URI uri;

    private MessageHandler messageHandler;

    private WebSocketClientHandler handler;

    private volatile AtomicInteger atomicCount = new AtomicInteger(0);

    public WebSocketClient initClient(String host, MessageHandler messageHandler) throws Exception {
        this.messageHandler = messageHandler;
        if (StringUtils.isEmpty(host)) {
            throw new RuntimeException("未配置host.");
        }
        uri = new URI(host);
        String scheme = uri.getScheme() == null? WssSchemeEnum.WS.getValue() : uri.getScheme();

        //判断是否ssl连接，如果是则设置为可信
        final boolean ssl = WssSchemeEnum.WSS.getValue().equalsIgnoreCase(scheme);
        final SslContext sslCtx;
        if (ssl) {
            sslCtx = SslContextBuilder.forClient()
                    .trustManager(InsecureTrustManagerFactory.INSTANCE).build();
        } else {
            sslCtx = null;
        }

        EventLoopGroup group = new NioEventLoopGroup();
        try {
            bootstrap = new Bootstrap();
            bootstrap.group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer() {
                        @Override
                        protected void initChannel(SocketChannel ch) {
                            ChannelPipeline p = ch.pipeline();
                            p.addFirst(new ChannelInboundHandlerAdapter() {
                                @Override
                                public void channelInactive(ChannelHandlerContext ctx) throws Exception {
                                    log.error("【{}】检测到wss断连, 第 {} 次发起重连.", exchange, atomicCount.incrementAndGet());
                                    super.channelInactive(ctx);
                                    ctx.channel().eventLoop().schedule(WebSocketClient.this::doConnect, 3000, TimeUnit.MILLISECONDS);
                                }
                            });
                            if (sslCtx != null) {
                                p.addLast(sslCtx.newHandler(ch.alloc(), uri.getHost(), getUriPort(uri)));
                            }
                            p.addLast(new HttpClientCodec());
                            p.addLast(new HttpObjectAggregator(8192));
                            p.addLast(WebSocketClientCompressionHandler.INSTANCE);
                            handler = new WebSocketClientHandler(
                                    WebSocketClientHandshakerFactory.newHandshaker(
                                            uri, WebSocketVersion.V13, null, true, new DefaultHttpHeaders()), exchange, messageHandler);
                            p.addLast(handler);
                        }
                    });
        } catch (Exception e) {
            log.error("wss创建client异常. e:", e);
            if (bootstrap != null) {
                bootstrap.config().group().shutdownGracefully();
            }
            throw new RuntimeException("初始化wss连接异常. e: " + e);
        }
        doConnect();
        return this;
    }

    public void doConnect() {
        try {
            ChannelFuture future = bootstrap.connect(uri.getHost(), getUriPort(uri)).sync();
            handler.handshakeFuture().sync();
            future.addListener((ChannelFutureListener) cf -> {
                        if (future.isSuccess()) {
                            channel = future.channel();
                            WssManger.addChannel(exchange, channel);
                            log.info("连接成功.");
                            messageHandler.connectSuccessAction(future.channel());
                            atomicCount.set(0);
                        } else {
                            log.error("监听断连, wss第 {} 次发起重连. ", atomicCount.incrementAndGet());
                            future.channel().eventLoop().schedule(WebSocketClient.this::doConnect, 3000, TimeUnit.MILLISECONDS);
                        }
                    });
        }catch (Exception e) {
            log.error("连接异常. e:" + e);
            if (bootstrap != null) {
                log.info("wss连接异常，第 {} 次发起重连.", atomicCount.incrementAndGet());
                bootstrap.config().group().schedule(WebSocketClient.this::doConnect, 3000, TimeUnit.MILLISECONDS);
            }
        }
    }

    /**
     * 根据URI获取对应的port
     *
     * @param uri uri
     * @return port
     */
    private int getUriPort(URI uri) {
        String scheme = uri.getScheme() == null? WssSchemeEnum.WS.getValue() : uri.getScheme();
        if (!WssSchemeEnum.allScheme().contains(scheme)) {
            throw new RuntimeException("Only WS(S) is supported.");
        }
        if (uri.getPort() == -1) {
            if (WssSchemeEnum.WS.getValue().equalsIgnoreCase(scheme)) {
                return WssSchemeEnum.WS.getPort();
            } else if (WssSchemeEnum.WSS.getValue().equalsIgnoreCase(scheme)) {
                return WssSchemeEnum.WSS.getPort();
            } else {
                return -1;
            }
        } else {
            return uri.getPort();
        }
    }
}