dubbo源码学习之服务端接收消息 负载均衡（四）

@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
    NettyChannel channel = NettyChannel.getOrAddChannel(ctx.getChannel(), url, handler);
    try {
        
        handler.received(channel, e.getMessage());
    } finally {
        NettyChannel.removeChannelIfDisconnected(ctx.getChannel());
    }
}

public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
    return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler))));
}

public NettyServer(URL url, ChannelHandler handler) throws RemotingException{
    super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
}

protected ChannelHandler wrapInternal(ChannelHandler handler, URL url) {
    return new MultiMessageHandler(new HeartbeatHandler(ExtensionLoader.getExtensionLoader(Dispatcher.class)
                                    .getAdaptiveExtension().dispatch(handler, url)));
}

public void received(Channel channel, Object message) throws RemotingException {
    channel.setAttribute(KEY_READ_TIMESTAMP, System.currentTimeMillis());
    ExchangeChannel exchangeChannel = HeaderExchangeChannel.getOrAddChannel(channel);
    try {
        if (message instanceof Request) {
            // handle request.
            Request request = (Request) message;
            if (request.isEvent()) {
                handlerEvent(channel, request);
            } else {
                if (request.isTwoWay()) {
                    //这里 ================
                    Response response = handleRequest(exchangeChannel, request);
                    channel.send(response);
                } else {
                    handler.received(exchangeChannel, request.getData());
                }
            }
        } else if (message instanceof Response) {
            handleResponse(channel, (Response) message);
        } else if (message instanceof String) {
            if (isClientSide(channel)) {
                Exception e = new Exception("Dubbo client can not supported string message: " + message + " in channel: " + channel + ", url: " + channel.getUrl());
                logger.error(e.getMessage(), e);
            } else {
                String echo = handler.telnet(channel, (String) message);
                if (echo != null && echo.length() > 0) {
                    channel.send(echo);
                }
            }
        } else {
            handler.received(exchangeChannel, message);
        }
    } finally {
        HeaderExchangeChannel.removeChannelIfDisconnected(channel);
    }
}

Response handleRequest(ExchangeChannel channel, Request req) throws RemotingException {
    Response res = new Response(req.getId(), req.getVersion());
    if (req.isBroken()) {
        Object data = req.getData();

        String msg;
        if (data == null) msg = null;
        else if (data instanceof Throwable) msg = StringUtils.toString((Throwable) data);
        else msg = data.toString();
        res.setErrorMessage("Fail to decode request due to: " + msg);
        res.setStatus(Response.BAD_REQUEST);

        return res;
    }
    // find handler by message class.
    Object msg = req.getData();
    try {
        // handle data.这里===================
        Object result = handler.reply(channel, msg);
        res.setStatus(Response.OK);
        res.setResult(result);
    } catch (Throwable e) {
        res.setStatus(Response.SERVICE_ERROR);
        res.setErrorMessage(StringUtils.toString(e));
    }
    return res;
}

private ExchangeHandler requestHandler = new ExchangeHandlerAdapter() {
    
    public Object reply(ExchangeChannel channel, Object message) throws RemotingException {
        if (message instanceof Invocation) {
            Invocation inv = (Invocation) message;
            Invoker<?> invoker = getInvoker(channel, inv);
            //如果是callback 需要处理高版本调用低版本的问题
            if (Boolean.TRUE.toString().equals(inv.getAttachments().get(IS_CALLBACK_SERVICE_INVOKE))){
                String methodsStr = invoker.getUrl().getParameters().get("methods");
                boolean hasMethod = false;
                if (methodsStr == null || methodsStr.indexOf(",") == -1){
                    hasMethod = inv.getMethodName().equals(methodsStr);
                } else {
                    String[] methods = methodsStr.split(",");
                    for (String method : methods){
                        if (inv.getMethodName().equals(method)){
                            hasMethod = true;
                            break;
                        }
                    }
                }
                if (!hasMethod){
                    logger.warn(new IllegalStateException("The methodName "+inv.getMethodName()+" not found in callback service interface ,invoke will be ignored. please update the api interface. url is:" + invoker.getUrl()) +" ,invocation is :"+inv );
                    return null;
                }
            }
            RpcContext.getContext().setRemoteAddress(channel.getRemoteAddress());
            //这里==========================
            return invoker.invoke(inv);
        }

wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments);