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dubbo源码更新两篇文章-dubbo完结，下次预计更新Spring源码系列文章
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docs/rpc/dubbo/06.Dubbo源码系列V1-Dubbo第六节-服务引入源码解析.md
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docs/rpc/dubbo/06.Dubbo源码系列V1-Dubbo第六节-服务引入源码解析.md
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docs/rpc/dubbo/07.Dubbo源码系列V1-Dubbo第七节-服务调用源码解析.md
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docs/rpc/dubbo/07.Dubbo源码系列V1-Dubbo第七节-服务调用源码解析.md
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---
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title: 07.Dubbo源码系列V1-Dubbo第七节-服务调用源码解析
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tags:
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- Dubbo
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- rpc
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categories:
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- rpc
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- Dubbo源码系列v1
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keywords: Dubbo，rpc
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description: 服务调用源码解析
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cover: 'https://cdn.jsdelivr.net/gh/youthlql/youthlql/img/dubbo.png'
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abbrlink: 84653c9d
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date: 2021-11-09 14:11:58
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---
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## 第七节: Dubbo服务调用源码解析
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### 服务导出的Netty启动源码
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> 最主要的就是构造一个Handler处理链路
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#### DubboProtocol
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```java
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public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
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URL url = invoker.getUrl();
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// 唯一标识一个服务的key
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String key = serviceKey(url);
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// 构造一个Exporter进行服务导出
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DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
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exporterMap.put(key, exporter);
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// 省略...
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// 开启NettyServer
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// 请求--->invocation--->服务key--->exporterMap.get(key)--->exporter--->invoker--->invoker.invoke(invocation)-->执行服务
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openServer(url);
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return exporter;
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}
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private void openServer(URL url) {
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// find server.
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String key = url.getAddress(); // 获得ip地址和port， 192.168.40.17:20880
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// NettyClient, NettyServer
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//client can export a service which's only for server to invoke
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boolean isServer = url.getParameter(IS_SERVER_KEY, true);
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if (isServer) {
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// 缓存Server对象
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ExchangeServer server = serverMap.get(key);
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// DCL，Double Check Lock
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if (server == null) {
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synchronized (this) {
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server = serverMap.get(key);
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if (server == null) {
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// 创建Server，并进行缓存
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serverMap.put(key, createServer(url));
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}
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}
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} else {
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// server supports reset, use together with override
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// 服务重新导出时，就会走这里
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server.reset(url);
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}
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}
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}
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private ExchangeServer createServer(URL url) {
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url = URLBuilder.from(url)
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// send readonly event when server closes, it's enabled by default
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.addParameterIfAbsent(CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString())
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// enable heartbeat by default
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.addParameterIfAbsent(HEARTBEAT_KEY, String.valueOf(DEFAULT_HEARTBEAT))
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.addParameter(CODEC_KEY, DubboCodec.NAME)
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.build();
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// 协议的服务器端实现类型，比如：dubbo协议的mina,netty等，http协议的jetty,servlet等，默认为netty
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String str = url.getParameter(SERVER_KEY, DEFAULT_REMOTING_SERVER);
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if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
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throw new RpcException("Unsupported server type: " + str + ", url: " + url);
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}
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// 通过url绑定端口，和对应的请求处理器
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ExchangeServer server;
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try {
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// requestHandler是请求处理器，类型为ExchangeHandler
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// 表示从url的端口接收到请求后，requestHandler来进行处理
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server = Exchangers.bind(url, requestHandler);
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} catch (RemotingException e) {
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throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e);
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}
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// 协议的客户端实现类型，比如：dubbo协议的mina,netty等
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str = url.getParameter(CLIENT_KEY);
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if (str != null && str.length() > 0) {
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Set<String> supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions();
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if (!supportedTypes.contains(str)) {
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throw new RpcException("Unsupported client type: " + str);
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}
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}
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return server;
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}
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```
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1. NettyClient<------>Socket连接，数据传输层<------>NettyServer。Netty这两端只要建立了连接就可以互相发送数据。
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2. ExchangeClient------数据交换层------ExchangeServer。这是Dubbo抽象出来的概念，主要就是抽象出了请求和响应这两个概念。
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3. ExchangeXXX里面包了Netty的东西
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```java
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private ExchangeHandler requestHandler = new ExchangeHandlerAdapter() {
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@Override
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public CompletableFuture<Object> reply(ExchangeChannel channel, Object message) throws RemotingException {
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if (!(message instanceof Invocation)) {
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throw new RemotingException(channel, "Unsupported request: "
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+ (message == null ? null : (message.getClass().getName() + ": " + message))
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+ ", channel: consumer: " + channel.getRemoteAddress() + " --> provider: " + channel.getLocalAddress());
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}
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// 转成Invocation对象，要开始用反射执行方法了
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Invocation inv = (Invocation) message;
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Invoker<?> invoker = getInvoker(channel, inv); // 服务实现者
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// need to consider backward-compatibility if it's a callback
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if (Boolean.TRUE.toString().equals(inv.getAttachments().get(IS_CALLBACK_SERVICE_INVOKE))) {
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String methodsStr = invoker.getUrl().getParameters().get("methods");
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boolean hasMethod = false;
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if (methodsStr == null || !methodsStr.contains(",")) {
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hasMethod = inv.getMethodName().equals(methodsStr);
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} else {
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String[] methods = methodsStr.split(",");
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for (String method : methods) {
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if (inv.getMethodName().equals(method)) {
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hasMethod = true;
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break;
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}
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}
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}
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if (!hasMethod) {
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logger.warn(new IllegalStateException("The methodName " + inv.getMethodName()
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+ " not found in callback service interface ,invoke will be ignored."
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+ " please update the api interface. url is:"
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+ invoker.getUrl()) + " ,invocation is :" + inv);
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return null;
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}
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}
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// 这里设置了，service中才能拿到remoteAddress
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RpcContext.getContext().setRemoteAddress(channel.getRemoteAddress());
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// 执行服务，得到结果
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Result result = invoker.invoke(inv);
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// 返回一个CompletableFuture
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return result.completionFuture().thenApply(Function.identity());
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}
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@Override
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public void received(Channel channel, Object message) throws RemotingException {
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if (message instanceof Invocation) {
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// 这是服务端接收到Invocation时的处理逻辑
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reply((ExchangeChannel) channel, message);
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} else {
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super.received(channel, message);
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}
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}
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private void invoke(Channel channel, String methodKey) {
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Invocation invocation = createInvocation(channel, channel.getUrl(), methodKey);
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if (invocation != null) {
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try {
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received(channel, invocation);
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} catch (Throwable t) {
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logger.warn("Failed to invoke event method " + invocation.getMethodName() + "(), cause: " + t.getMessage(), t);
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}
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}
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}
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};
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Invoker<?> getInvoker(Channel channel, Invocation inv) throws RemotingException {
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boolean isCallBackServiceInvoke = false;
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boolean isStubServiceInvoke = false;
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int port = channel.getLocalAddress().getPort();
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String path = inv.getAttachments().get(PATH_KEY);
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// if it's callback service on client side
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isStubServiceInvoke = Boolean.TRUE.toString().equals(inv.getAttachments().get(STUB_EVENT_KEY));
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if (isStubServiceInvoke) {
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port = channel.getRemoteAddress().getPort();
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}
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//callback
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isCallBackServiceInvoke = isClientSide(channel) && !isStubServiceInvoke;
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if (isCallBackServiceInvoke) {
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path += "." + inv.getAttachments().get(CALLBACK_SERVICE_KEY);
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inv.getAttachments().put(IS_CALLBACK_SERVICE_INVOKE, Boolean.TRUE.toString());
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}
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// 从请求中拿到serviceKey，从exporterMap中拿到已经导出了的服务
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String serviceKey = serviceKey(port, path, inv.getAttachments().get(VERSION_KEY), inv.getAttachments().get(GROUP_KEY));
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DubboExporter<?> exporter = (DubboExporter<?>) exporterMap.get(serviceKey);
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if (exporter == null) {
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throw new RemotingException(channel, "Not found exported service: " + serviceKey + " in " + exporterMap.keySet() + ", may be version or group mismatch " +
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", channel: consumer: " + channel.getRemoteAddress() + " --> provider: " + channel.getLocalAddress() + ", message:" + inv);
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}
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// 拿到服务对应的Invoker
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return exporter.getInvoker();
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}
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```
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#### Exchangers
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```java
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public static ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
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if (url == null) {
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throw new IllegalArgumentException("url == null");
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}
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if (handler == null) {
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throw new IllegalArgumentException("handler == null");
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}
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// codec表示协议编码方式
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url = url.addParameterIfAbsent(Constants.CODEC_KEY, "exchange");
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// 通过url得到HeaderExchanger， 利用HeaderExchanger进行bind，将得到一个HeaderExchangeServer
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return getExchanger(url).bind(url, handler);
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}
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```
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#### HeaderExchange
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```java
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@Override
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public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
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// 下面会去启动Netty
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// 对handler包装了两层，表示当处理一个请求时，每层Handler负责不同的处理逻辑
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// 为什么在connect和bind时都是DecodeHandler，解码，解的是把InputStream解析成RpcInvocation对象
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// DecodeHandler -> HeaderExchangeHandler -> DubboProtocol(ExchangeHandlerAdapter) 一层一层包
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// 上面的handler处理完了交给下面的handler
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return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler))));
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}
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```
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#### HeaderExchangeServer
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HeaderExchangeServer里有一个server属性,这个server就是NettyServer
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```java
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private final Server server;
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//启动netty的时候会调用这个
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public HeaderExchangeServer(Server server) {
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Assert.notNull(server, "server == null");
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this.server = server;
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// 启动定义关闭Channel(socket)的Task
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startIdleCheckTask(getUrl());
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}
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```
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#### Transporters
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```java
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public static Server bind(URL url, ChannelHandler... handlers) throws RemotingException {
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if (url == null) {
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throw new IllegalArgumentException("url == null");
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}
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if (handlers == null || handlers.length == 0) {
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throw new IllegalArgumentException("handlers == null");
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}
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// 如果bind了多个handler，那么当有一个连接过来时，会循环每个handler去处理连接
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ChannelHandler handler;
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if (handlers.length == 1) {
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handler = handlers[0];
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} else {
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handler = new ChannelHandlerDispatcher(handlers);
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}
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// 调用NettyTransporter去绑定，Transporter表示网络传输层
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return getTransporter().bind(url, handler);
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}
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public static Transporter getTransporter() {
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//@SPI默认配置的就是netty
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return ExtensionLoader.getExtensionLoader(Transporter.class).getAdaptiveExtension();
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}
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```
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#### NettyTransporter
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```java
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@Override
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public Server bind(URL url, ChannelHandler listener) throws RemotingException {
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return new NettyServer(url, listener);
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}
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```
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#### NettyServer
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```java
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public NettyServer(URL url, ChannelHandler handler) throws RemotingException {
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//多个handler一层一层的包装，有点像责任链模式，这个handler处理完了，交给下一个handler
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super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
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}
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```
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#### ChannelHandlers
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```java
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public class ChannelHandlers {
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// 单例模式
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private static ChannelHandlers INSTANCE = new ChannelHandlers();
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protected ChannelHandlers() {
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}
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public static ChannelHandler wrap(ChannelHandler handler, URL url) {
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return ChannelHandlers.getInstance().wrapInternal(handler, url);
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}
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protected static ChannelHandlers getInstance() {
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return INSTANCE;
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}
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static void setTestingChannelHandlers(ChannelHandlers instance) {
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INSTANCE = instance;
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}
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protected ChannelHandler wrapInternal(ChannelHandler handler, URL url) {
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// 先通过ExtensionLoader.getExtensionLoader(Dispatcher.class).getAdaptiveExtension().dispatch(handler, url)
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// 得到一个AllChannelHandler(handler, url)
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// 然后把AllChannelHandler包装成HeartbeatHandler，HeartbeatHandler包装成MultiMessageHandler
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// 所以当Netty接收到一个数据时，会经历MultiMessageHandler--->HeartbeatHandler---->AllChannelHandler
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// 而AllChannelHandler会调用handler
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return new MultiMessageHandler(new HeartbeatHandler(ExtensionLoader.getExtensionLoader(Dispatcher.class)
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||||
.getAdaptiveExtension().dispatch(handler, url)));
|
||||
}
|
||||
|
||||
}
|
||||
```
|
||||
|
||||
然后回到NettyServer调用super(XXX)，走到AbstractServer
|
||||
|
||||
#### AbstractServer
|
||||
|
||||
```java
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||||
public AbstractServer(URL url, ChannelHandler handler) throws RemotingException {
|
||||
super(url, handler);
|
||||
localAddress = getUrl().toInetSocketAddress();
|
||||
|
||||
String bindIp = getUrl().getParameter(Constants.BIND_IP_KEY, getUrl().getHost());
|
||||
int bindPort = getUrl().getParameter(Constants.BIND_PORT_KEY, getUrl().getPort());
|
||||
if (url.getParameter(ANYHOST_KEY, false) || NetUtils.isInvalidLocalHost(bindIp)) {
|
||||
bindIp = ANYHOST_VALUE;
|
||||
}
|
||||
bindAddress = new InetSocketAddress(bindIp, bindPort);
|
||||
this.accepts = url.getParameter(ACCEPTS_KEY, DEFAULT_ACCEPTS);
|
||||
this.idleTimeout = url.getParameter(IDLE_TIMEOUT_KEY, DEFAULT_IDLE_TIMEOUT);
|
||||
try {
|
||||
doOpen();//走到NettyServer
|
||||
if (logger.isInfoEnabled()) {
|
||||
logger.info("Start " + getClass().getSimpleName() + " bind " + getBindAddress() + ", export " + getLocalAddress());
|
||||
}
|
||||
} catch (Throwable t) {
|
||||
throw new RemotingException(url.toInetSocketAddress(), null, "Failed to bind " + getClass().getSimpleName()
|
||||
+ " on " + getLocalAddress() + ", cause: " + t.getMessage(), t);
|
||||
}
|
||||
//fixme replace this with better method
|
||||
DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension();
|
||||
executor = (ExecutorService) dataStore.get(Constants.EXECUTOR_SERVICE_COMPONENT_KEY, Integer.toString(url.getPort()));
|
||||
}
|
||||
```
|
||||
|
||||
#### NettyServer
|
||||
|
||||
```java
|
||||
protected void doOpen() throws Throwable {
|
||||
bootstrap = new ServerBootstrap();
|
||||
|
||||
bossGroup = new NioEventLoopGroup(1, new DefaultThreadFactory("NettyServerBoss", true));
|
||||
workerGroup = new NioEventLoopGroup(getUrl().getPositiveParameter(IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS),
|
||||
new DefaultThreadFactory("NettyServerWorker", true));
|
||||
|
||||
//最终再包装一个NettyServerHandler，这个就是最外层的Handler，请求来了它是第一个处理的
|
||||
final NettyServerHandler nettyServerHandler = new NettyServerHandler(getUrl(), this);
|
||||
channels = nettyServerHandler.getChannels();
|
||||
|
||||
bootstrap.group(bossGroup, workerGroup)
|
||||
.channel(NioServerSocketChannel.class)
|
||||
.childOption(ChannelOption.TCP_NODELAY, Boolean.TRUE)
|
||||
.childOption(ChannelOption.SO_REUSEADDR, Boolean.TRUE)
|
||||
.childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT)
|
||||
.childHandler(new ChannelInitializer<NioSocketChannel>() {
|
||||
@Override
|
||||
protected void initChannel(NioSocketChannel ch) throws Exception {
|
||||
// FIXME: should we use getTimeout()?
|
||||
int idleTimeout = UrlUtils.getIdleTimeout(getUrl());
|
||||
// 这里就会拿到DubboCodec，接收到数据之后就会进行解码
|
||||
NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyServer.this);
|
||||
ch.pipeline()//.addLast("logging",new LoggingHandler(LogLevel.INFO))//for debug
|
||||
.addLast("decoder", adapter.getDecoder())
|
||||
.addLast("encoder", adapter.getEncoder())
|
||||
.addLast("server-idle-handler", new IdleStateHandler(0, 0, idleTimeout, MILLISECONDS))
|
||||
.addLast("handler", nettyServerHandler);
|
||||
}
|
||||
});
|
||||
// bind
|
||||
ChannelFuture channelFuture = bootstrap.bind(getBindAddress());
|
||||
channelFuture.syncUninterruptibly();
|
||||
channel = channelFuture.channel();
|
||||
|
||||
}
|
||||
```
|
||||
|
||||
|
||||
|
||||
#### 分割
|
||||
|
||||
### 服务提供端执行逻辑
|
||||
|
||||
#### 概述
|
||||
|
||||
1. NettyServerHandler：接收数据
|
||||
2. MultiMessageHandler：判断接收到的数据是否是MultiMessage，如果是则获取MultiMessage中的单个Message，传递给HeartbeatHandler进行处理
|
||||
3. HeartbeatHandler：判断是不是心跳消息，如果是不是则把Message传递给AllChannelHandler
|
||||
4. AllChannelHandler：把接收到的Message封装为一个ChannelEventRunnable对象，扔给线程池进行处理
|
||||
5. ChannelEventRunnable：在ChannelEventRunnable的run方法中会调用DecodeHandler处理Message
|
||||
6. DecodeHandler：按Dubbo协议的数据格式，解析当前请求的path，versio，方法，方法参数等等，然后把解析好了的请求交给HeaderExchangeHandler
|
||||
7. HeaderExchangeHandler：处理Request数据，首先构造一个Response对象，然后调用ExchangeHandlerAdapter得到一个CompletionStage future，然后给future通过whenComplete绑定一个回调函数，当future执行完了之后，就可以从回调函数中得到ExchangeHandlerAdapter的执行结果，并把执行结果设置给Response对象，通过channel发送出去。
|
||||
8. ExchangeHandlerAdapter：从本机已经导出的Exporter中根据当前Request所对应的服务key，去寻找Exporter对象，从Exporter中得到Invoker，然后执行invoke方法，此Invoker为ProtocolFilterWrapper$CallbackRegistrationInvoker
|
||||
9. ProtocolFilterWrapper$CallbackRegistrationInvoker：负责执行过滤器链，并且在执行完了之后回调每个过滤器的onResponse或onError方法
|
||||
10. EchoFilter：判断当前请求是不是一个回升测试，如果是，则不继续执行过滤器链了（服务实现者Invoker也不会调用了）
|
||||
11. ClassLoaderFilter：设置当前线程的classloader为当前要执行的服务接口所对应的classloader
|
||||
12. GenericFilter：把泛化调用发送过来的信息包装为RpcInvocation对象
|
||||
13. ContextFilter：设置RpcContext.getContext()的参数
|
||||
14. TraceFilter：先执行下一个invoker的invoke方法，调用成功后录调用信息
|
||||
15. TimeoutFilter：调用时没有特别处理，只是记录了一下当前时间，当整个filter链都执行完了之后回调TimeoutFilter的onResponse方法时，会判断本次调用是否超过了timeout
|
||||
16. MonitorFilter：记录当前服务的执行次数
|
||||
17. ExceptionFilter：调用时没有特别处理，在回调onResponse方法时，对不同的异常进行处理，详解Dubbo的异常处理
|
||||
18. DelegateProviderMetaDataInvoker：过滤器链结束，调用下一个Invoker
|
||||
19. AbstractProxyInvoker：在服务导出时，根据服务接口，服务实现类对象生成的，它的invoke方法就会执行服务实现类对象的方法，得到结果
|
||||
|
||||
#### JavassistProxyFactory
|
||||
|
||||
```java
|
||||
public class JavassistProxyFactory extends AbstractProxyFactory {
|
||||
|
||||
@Override
|
||||
@SuppressWarnings("unchecked")
|
||||
public <T> T getProxy(Invoker<T> invoker, Class<?>[] interfaces) {
|
||||
return (T) Proxy.getProxy(interfaces).newInstance(new InvokerInvocationHandler(invoker));
|
||||
}
|
||||
|
||||
@Override
|
||||
public <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) {
|
||||
|
||||
// TODO Wrapper cannot handle this scenario correctly: the classname contains '$'
|
||||
// 如果现在被代理的对象proxy本身就是一个已经被代理过的对象，那么则取代理类的Wrapper，否则取type（接口）的Wrapper
|
||||
// Wrapper是针对某个类或某个接口的包装类，通过wrapper对象可以更方便的去执行某个类或某个接口的方法
|
||||
final Wrapper wrapper = Wrapper.getWrapper(proxy.getClass().getName().indexOf('$') < 0 ? proxy.getClass() : type);
|
||||
|
||||
// proxy是服务实现类
|
||||
// type是服务接口
|
||||
// url是一个注册中心url，但同时也记录了
|
||||
return new AbstractProxyInvoker<T>(proxy, type, url) {
|
||||
@Override
|
||||
protected Object doInvoke(T proxy, String methodName,
|
||||
Class<?>[] parameterTypes,
|
||||
Object[] arguments) throws Throwable {
|
||||
|
||||
// 执行proxy的method方法
|
||||
// 执行的proxy实例的方法
|
||||
// 如果没有wrapper，则要通过原生的反射技术去获取Method对象，然后执行
|
||||
return wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments);
|
||||
}
|
||||
};
|
||||
}
|
||||
|
||||
}
|
||||
```
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
### 服务消费端执行逻辑
|
||||
|
||||
|
||||
|
||||
1. MockClusterInvoker.invoke(new RpcInvocation(method, args))：Mock逻辑
|
||||
2. AbstractClusterInvoker.invoke(invocation)：把RpcContext中设置的Attachments添加到invocation对象上，调用路由链从服务目录上筛选出适合的服务Invoker，获得服务均衡策略loadbalance
|
||||
3. FailoverClusterInvoker.doInvoke(invocation, invokers, loadbalance)：根据负载均衡策略选出一个invoker，然后执行
|
||||
4. InvokerWrapper.invoke(invocation)：没做什么事情
|
||||
5. CallbackRegistrationInvoker.invoke(invocation)：开始执行Filter链，执行完得到结果后，会获取ListenableFilter中的listener，执行listener的onResponse方法
|
||||
6. ConsumerContextFilter.invoke(invocation)：设置RpcContext中LocalAddress、RemoteAddress、RemoteApplicationName参数
|
||||
7. FutureFilter.invoke(invocation)：
|
||||
8. MonitorFilter.invoke(invocation)：方法的执行次数+1
|
||||
9. ListenerInvokerWrapper.invoke(invocation)：没做什么事情
|
||||
10. AsyncToSyncInvoker.invoke(invocation)：异步转同步，会先用下层Invoker去异步执行，然后阻塞Integer.MAX_VALUE时间，直到拿到了结果
|
||||
11. AbstractInvoker.invoke(invocation)：主要调用DubboInvoker的doInvoke方法，如果doInvoker方法出现了异常，会进行包装，包装成AsyncRpcResult
|
||||
12. DubboInvoker.doInvoke(invocation)：从clients轮询出一个client进行数据发送，如果配置了不关心结果，则调用ReferenceCountExchangeClient的send方法，否则调用ReferenceCountExchangeClient的request方法
|
||||
13. ReferenceCountExchangeClient.request(Object request, int timeout)：没做什么事情
|
||||
14. HeaderExchangeClient.request(Object request, int timeout)：没做什么事情
|
||||
15. HeaderExchangeChannel.request(Object request, int timeout)：构造一个Request对象，并且会构造一个DefaultFuture对象来阻塞timeout的时间来等待结果，在构造DefaultFuture对象时，会把DefaultFuture对象和req的id存入FUTURES中，FUTURES是一个Map，当HeaderExchangeHandler接收到结果时，会从这个Map中根据id获取到DefaultFuture对象，然后返回Response。
|
||||
16. AbstractPeer.send(Object message)：从url中获取send参数，默认为false
|
||||
17. AbstractClient.send(Object message, boolean sent)：没做什么
|
||||
18. NettyChannel.send(Object message, boolean sent)：调用NioSocketChannel的writeAndFlush发送数据，然后判断send如果是true，那么则阻塞url中指定的timeout时间，因为如果send是false，在HeaderExchangeChannel中会阻塞timeout时间
|
||||
19. NioSocketChannel.writeAndFlush(Object msg)：最底层的Netty非阻塞式的发送数据
|
||||
|
||||
|
||||
|
||||
总结一下上面调用流程：
|
||||
|
||||
1. 最外层是Mock逻辑，调用前，调用后进行Mock
|
||||
2. 从服务目录中，根据当前调用的方法和路由链，筛选出部分服务Invoker（DubboInvoker）
|
||||
3. 对服务Invoker进行负载均衡，选出一个服务Invoker
|
||||
4. 执行Filter链
|
||||
5. AsyncToSyncInvoker完成异步转同步，因为DubboInvoker的执行是异步非阻塞的，所以如果是同步调用，则会在此处阻塞，知道拿到响应结果
|
||||
6. DubboInvoker开始异步非阻塞的调用
|
||||
7. HeaderExchangeChannel中会阻塞timeout的时间来等待结果，该timeout就是用户在消费端所配置的timeout
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
### Dubbo的异常处理
|
||||
|
||||
当服务消费者在调用一个服务时，服务提供者在执行服务逻辑时可能会出现异常，对于Dubbo来说，服务消费者需要在消费端抛出这个异常，那么这个功能是怎么做到的呢？
|
||||
|
||||
|
||||
|
||||
服务提供者在执行服务时，如果出现了异常，那么框架会把异常捕获，捕获异常的逻辑在AbstractProxyInvoker中，捕获到异常后，会把异常信息包装为正常的AppResponse对象，只是AppResponse的value属性没有值，exception属性有值。
|
||||
|
||||
|
||||
|
||||
此后，服务提供者会把这个AppResponse对象发送给服务消费端，服务消费端是在InvokerInvocationHandler中调用AppResponse的recreate方法重新得到一个结果，在recreate方法中会去失败AppResponse对象是否正常，也就是是否存在exception信息，如果存在，则直接throw这个exception，从而做到**服务执行时出现的异常，在服务消费端抛出**。
|
||||
|
||||
|
||||
|
||||
那么这里存在一个问题，如果服务提供者抛出的异常类，在服务消费者这边不存在，那么服务消费者也就抛不出这个异常了，那么dubbo是怎么处理的呢？
|
||||
|
||||
|
||||
|
||||
这里就涉及到了ExceptionFilter，它是服务提供者端的一个过滤器，它主要是在服务提供者执行完服务后会去识别异常：
|
||||
|
||||
1. 如果是需要开发人员捕获的异常，那么忽略，直接把这个异常返回给消费者
|
||||
2. 如果在当前所执行的方法签名上有声明，那么忽略，直接把这个异常返回给消费者
|
||||
3. 如果抛出的异常不需要开发人员捕获，或者方法上没有申明，那么服务端或记录一个error日志
|
||||
4. 异常类和接口类在同一jar包里，那么忽略，直接把这个异常返回给消费者
|
||||
5. 如果异常类是JDK自带的异常，那么忽略，直接把这个异常返回给消费者
|
||||
6. 如果异常类是Dubbo自带的异常，那么忽略，直接把这个异常返回给消费者
|
||||
7. **否则，把异常信息包装成RuntimeException，并覆盖AppResponse对象中的exception属性**
|
||||
Reference in New Issue
Block a user