本文将深入分析dubbo的服务发布涉及到的流程及主要类的代码。首先，我们先从类的关系图来看一下dubbo发布服务涉及到的相关类。
1.类图
上图展示了部分服务发布过程中需要使用到的类和接口，其中：
spring适配涉及到的类：DubboNamespaceHandler、DubboBeanDefinitionParser、ServiceBean;
配置信息存储：ServicdConfig、RegistryConfig、MonitorConfig、ProtocolConfig、ProviderConfig等；
应用协议：Protocol、DubboProtocol、HessianProtocol、ThriftProtocol、RmiProtocol、AbstractProxyProtocol、AbstractProtocol等；
Server相关：Exchanger、HeaderExchanger、ExchangeServer、HeaderExchangeServer、Transporters、Transporter、NettyTransporter、NettyServer等；
2.时序图
我们通过时序图来分析一下在发布服务的过程中，上面的类是如何串联在一起的：
a.spring容器通过DubboBeanDefinitionParser类的对象来解析xml文件中的标签，生成ServiceConfig等配置对象；
b.ServiceConfig的export()等发布服务的方法被调用；
c.通过spi机制确定Protocol接口的实现对象为DubboProtocol的对象，调用它的openServer()等方法；
d.通过spi机制确定Transporter接口的实现对象为NettyTransporter，调用它的bind()方法；
e.调用NettyServer类，启动netty服务，绑定端口。
3.核心代码解析
a.DubboProtocol
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
URL url = invoker.getUrl();//获取url信息
// export service.
String key = serviceKey(url);//产生与发布的接口映射的key ,格式例如：com.alibaba.dubbo.demo.DemoService:20882
DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);//创建DubboExporter对象
exporterMap.put(key, exporter);//缓存此对象
//export an stub service for dispaching event
Boolean isStubSupportEvent = url.getParameter(Constants.STUB_EVENT_KEY,Constants.DEFAULT_STUB_EVENT);
Boolean isCallbackservice = url.getParameter(Constants.IS_CALLBACK_SERVICE, false);
if (isStubSupportEvent && !isCallbackservice){
String stubServiceMethods = url.getParameter(Constants.STUB_EVENT_METHODS_KEY);
if (stubServiceMethods == null || stubServiceMethods.length() == 0 ){
if (logger.isWarnEnabled()){
logger.warn(new IllegalStateException("consumer [" +url.getParameter(Constants.INTERFACE_KEY) +
"], has set stubproxy support event ,but no stub methods founded."));
}
} else {
stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
}
}
openServer(url);//打开服务
return exporter;
}
private void openServer(URL url) {
// find server.
String key = url.getAddress();
//client 也可以暴露一个只有server可以调用的服务。
boolean isServer = url.getParameter(Constants.IS_SERVER_KEY,true);
if (isServer) {
ExchangeServer server = serverMap.get(key);
if (server == null) {
serverMap.put(key, createServer(url));//创建新的服务
} else {
//server支持reset,配合override功能使用
server.reset(url);
}
}
}
private ExchangeServer createServer(URL url) {
//默认开启server关闭时发送readonly事件
url = url.addParameterIfAbsent(Constants.CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString());
//默认开启heartbeat
url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));
String str = url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_SERVER);
if (str != null && str.length() > 0 && ! ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str))
throw new RpcException("Unsupported server type: " + str + ", url: " + url);
url = url.addParameter(Constants.CODEC_KEY, Version.isCompatibleVersion() ? COMPATIBLE_CODEC_NAME : DubboCodec.NAME);
ExchangeServer server;
try {
server = Exchangers.bind(url, requestHandler);
} catch (RemotingException e) {
throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e);
}
str = url.getParameter(Constants.CLIENT_KEY);
if (str != null && str.length() > 0) {
Set<String> supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions();
if (!supportedTypes.contains(str)) {
throw new RpcException("Unsupported client type: " + str);
}
}
return server;
}
b.NettyServer
protected void doOpen() throws Throwable {
NettyHelper.setNettyLoggerFactory();
ExecutorService boss = Executors.newCachedThreadPool(new NamedThreadFactory("NettyServerBoss", true));//boss线程池
ExecutorService worker = Executors.newCachedThreadPool(new NamedThreadFactory("NettyServerWorker", true));//工作线程池
ChannelFactory channelFactory = new NioServerSocketChannelFactory(boss, worker, getUrl().getPositiveParameter(Constants.IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS));
bootstrap = new ServerBootstrap(channelFactory);//服务启动类
final NettyHandler nettyHandler = new NettyHandler(getUrl(), this);
channels = nettyHandler.getChannels();
// https://issues.jboss.org/browse/NETTY-365
// https://issues.jboss.org/browse/NETTY-379
// final Timer timer = new HashedWheelTimer(new NamedThreadFactory("NettyIdleTimer", true));
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
public ChannelPipeline getPipeline() {
NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec() ,getUrl(), NettyServer.this);
ChannelPipeline pipeline = Channels.pipeline();
/*int idleTimeout = getIdleTimeout();
if (idleTimeout > 10000) {
pipeline.addLast("timer", new IdleStateHandler(timer, idleTimeout / 1000, 0, 0));
}*/
pipeline.addLast("decoder", adapter.getDecoder());//增加解码器
pipeline.addLast("encoder", adapter.getEncoder());//增加编码器
pipeline.addLast("handler", nettyHandler);//业务处理类
return pipeline;
}
});
// bind
channel = bootstrap.bind(getBindAddress());
}