Dubbo接收request的过程其实和client端接收response的过程有点像。建议先阅读上一篇文章。
从NettyHandler开始受到tcp请求，再一直传递到HeaderExchangeHandler的过程和client端接收response过程基本一样，不再详细描述.
@Override
public void received(Channel channel, Object message) throws RemotingException {
channel.setAttribute(KEY_READ_TIMESTAMP, System.currentTimeMillis());
final 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()) {
//处理request请求
handleRequest(exchangeChannel, request);
} else {
handler.received(exchangeChannel, request.getData());
}
}
} else if (message instanceof Response) {
//处理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);
}
}
void handleRequest(final ExchangeChannel channel, Request req) throws RemotingException {
Response res = new Response(req.getId(), req.getVersion());
//暂时不理解这个Broken是什么意思
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);
channel.send(res);
return;
}
// find handler by message class.
Object msg = req.getData();
try {
// handle data.
//代码执行到这里，就是开始调用我们实现的业务代码去获取数据
//这个handler就是DubboProtocol里的handler对象，调用其reply()方法执行，通过放射执行业务代码获取数据
CompletableFuture<Object> future = handler.reply(channel, msg);
if (future.isDone()) {
res.setStatus(Response.OK);
res.setResult(future.get());
channel.send(res);
return;
}
future.whenComplete((result, t) -> {
try {
if (t == null) {
res.setStatus(Response.OK);
res.setResult(result);
} else {
res.setStatus(Response.SERVICE_ERROR);
res.setErrorMessage(StringUtils.toString(t));
}
//把拿到的response写出去
channel.send(res);
} catch (RemotingException e) {
logger.warn("Send result to consumer failed, channel is " + channel + ", msg is " + e);
} finally {
// HeaderExchangeChannel.removeChannelIfDisconnected(channel);
}
});
} catch (Throwable e) {
res.setStatus(Response.SERVICE_ERROR);
res.setErrorMessage(StringUtils.toString(e));
channel.send(res);
}
}
当拿到response之后就会把response写出去，这里的channel对象就是HeaderExchangeChannel,后面会转发NettyChannel对象把数据写出去.
下面看下DubboProtocol里的handler的reply实现:
private ExchangeHandler requestHandler = new ExchangeHandlerAdapter() {
@Override
public CompletableFuture<Object> reply(ExchangeChannel channel, Object message) throws RemotingException {
if (message instanceof Invocation) {
Invocation inv = (Invocation) message;
Invoker<?> invoker = getInvoker(channel, inv);
// need to consider backward-compatibility if it's a callback
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.contains(",")) {
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 rpcContext = RpcContext.getContext();
boolean supportServerAsync = invoker.getUrl().getMethodParameter(inv.getMethodName(), Constants.ASYNC_KEY, false);
if (supportServerAsync) {
CompletableFuture<Object> future = new CompletableFuture<>();
rpcContext.setAsyncContext(new AsyncContextImpl(future));
}
rpcContext.setRemoteAddress(channel.getRemoteAddress());
//获取Invoker对象执行invoke
//这里会把filter执行一遍然后拿到结果
Result result = invoker.invoke(inv);
if (result instanceof AsyncRpcResult) {
return ((AsyncRpcResult) result).getResultFuture().thenApply(r -> (Object) r);
} else {
return CompletableFuture.completedFuture(result);
}
}
throw new RemotingException(channel, "Unsupported request: "
+ (message == null ? null : (message.getClass().getName() + ": " + message))
+ ", channel: consumer: " + channel.getRemoteAddress() + " --> provider: " + channel.getLocalAddress());
}
...省略
};
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