版权声明：本文为博主原创文章，转载请注明出处。 https://blog.csdn.net/heroqiang/article/details/82766196
阅读须知
- dubbo版本：2.6.0
- spring版本：4.3.8
- 文章中使用/* */注释的方法会做深入分析
正文
承接provider初始化篇，本篇文章我们来分析provider的暴露过程。
ServiceConfig：
private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
String name = protocolConfig.getName();
if (name == null || name.length() == 0) {
name = "dubbo";
}
Map<String, String> map = new HashMap<String, String>();
map.put(Constants.SIDE_KEY, Constants.PROVIDER_SIDE);
map.put(Constants.DUBBO_VERSION_KEY, Version.getVersion());
map.put(Constants.TIMESTAMP_KEY, String.valueOf(System.currentTimeMillis()));
if (ConfigUtils.getPid() > 0) {
map.put(Constants.PID_KEY, String.valueOf(ConfigUtils.getPid()));
}
// 为几个配置追加参数
appendParameters(map, application);
appendParameters(map, module);
appendParameters(map, provider, Constants.DEFAULT_KEY);
appendParameters(map, protocolConfig);
appendParameters(map, this);
// method配置
if (methods != null && methods.size() > 0) {
for (MethodConfig method : methods) {
// 追加参数
appendParameters(map, method, method.getName());
String retryKey = method.getName() + ".retry";
// retry设置
if (map.containsKey(retryKey)) {
String retryValue = map.remove(retryKey);
if ("false".equals(retryValue)) {
map.put(method.getName() + ".retries", "0");
}
}
List<ArgumentConfig> arguments = method.getArguments();
// 转换参数类型
if (arguments != null && arguments.size() > 0) {
for (ArgumentConfig argument : arguments) {
if (argument.getType() != null && argument.getType().length() > 0) {
Method[] methods = interfaceClass.getMethods();
if (methods != null && methods.length > 0) {
// 遍历接口的所有方法
for (int i = 0; i < methods.length; i++) {
String methodName = methods[i].getName();
// 目标方法和签名
if (methodName.equals(method.getName())) {
Class<?>[] argtypes = methods[i].getParameterTypes();
// 参数索引-1表示未设置
if (argument.getIndex() != -1) {
if (argtypes[argument.getIndex()].getName().equals(argument.getType())) {
// 追加参数
appendParameters(map, argument, method.getName() + "." + argument.getIndex());
} else {
throw new IllegalArgumentException("argument config error : the index attribute and type attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType());
}
} else {
// 方法中的多个回调
for (int j = 0; j < argtypes.length; j++) {
Class<?> argclazz = argtypes[j];
if (argclazz.getName().equals(argument.getType())) {
appendParameters(map, argument, method.getName() + "." + j);
if (argument.getIndex() != -1 && argument.getIndex() != j) {
throw new IllegalArgumentException("argument config error : the index attribute and type attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType());
}
}
}
}
}
}
}
} else if (argument.getIndex() != -1) {
appendParameters(map, argument, method.getName() + "." + argument.getIndex());
} else {
throw new IllegalArgumentException("argument config must set index or type attribute.eg: <dubbo:argument index='0' .../> or <dubbo:argument type=xxx .../>");
}
}
}
}
}
// 判断服务是否是GenericService类型
if (ProtocolUtils.isGeneric(generic)) {
map.put("generic", generic);
map.put("methods", Constants.ANY_VALUE);
} else {
String revision = Version.getVersion(interfaceClass, version);
if (revision != null && revision.length() > 0) {
map.put("revision", revision);
}
// 使用javaassist生成接口的包装类，获取方法名称
String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
if (methods.length == 0) {
logger.warn("NO method found in service interface " + interfaceClass.getName());
map.put("methods", Constants.ANY_VALUE);
} else {
map.put("methods", StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ","));
}
}
// token配置
if (!ConfigUtils.isEmpty(token)) {
if (ConfigUtils.isDefault(token)) {
map.put("token", UUID.randomUUID().toString());
} else {
map.put("token", token);
}
}
// 协议的名称配置为injvm
if ("injvm".equals(protocolConfig.getName())) {
protocolConfig.setRegister(false);
map.put("notify", "false");
}
// contextPath配置
String contextPath = protocolConfig.getContextpath();
if ((contextPath == null || contextPath.length() == 0) && provider != null) {
contextPath = provider.getContextpath();
}
/* 注册并绑定服务提供者的IP地址，可以单独配置 */
String host = this.findConfigedHosts(protocolConfig, registryURLs, map);
/* 为提供者注册端口和绑定端口，可以单独配置 */
Integer port = this.findConfigedPorts(protocolConfig, name, map);
URL url = new URL(name, host, port, (contextPath == null || contextPath.length() == 0 ? "" : contextPath + "/") + path, map);
if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
.hasExtension(url.getProtocol())) {
url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
.getExtension(url.getProtocol()).getConfigurator(url).configure(url);
}
String scope = url.getParameter(Constants.SCOPE_KEY);
// scope配置为none不暴露服务
if (!Constants.SCOPE_NONE.toString().equalsIgnoreCase(scope)) {
if (!Constants.SCOPE_REMOTE.toString().equalsIgnoreCase(scope)) {
/* 没有配置为remote，暴露本地服务 */
exportLocal(url);
}
// 没有配置为local，暴露远程服务
if (!Constants.SCOPE_LOCAL.toString().equalsIgnoreCase(scope)) {
if (logger.isInfoEnabled()) {
logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);
}
// 判断是否有注册中心配置
if (registryURLs != null && registryURLs.size() > 0) {
for (URL registryURL : registryURLs) {
url = url.addParameterIfAbsent("dynamic", registryURL.getParameter("dynamic"));
// 加载监视器地址
URL monitorUrl = loadMonitor(registryURL);
if (monitorUrl != null) {
url = url.addParameterAndEncoded(Constants.MONITOR_KEY, monitorUrl.toFullString());
}
if (logger.isInfoEnabled()) {
logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL);
}
// 获取invoker
Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));
DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
/* 暴露服务 */
Exporter<?> exporter = protocol.export(wrapperInvoker);
exporters.add(exporter);
}
} else {
Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, url);
DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
Exporter<?> exporter = protocol.export(wrapperInvoker);
exporters.add(exporter);
}
}
}
this.urls.add(url);
}
ServiceConfig：
private String findConfigedHosts(ProtocolConfig protocolConfig, List<URL> registryURLs, Map<String, String> map) {
boolean anyhost = false;
// 从系统属性中获取dubbo ip绑定配置，如果是非法ip（空、localhost、0.0.0.0、127.*.*.*都属于非法），抛出异常
String hostToBind = getValueFromConfig(protocolConfig, Constants.DUBBO_IP_TO_BIND);
// 如果从环境中没有获取到配置，继续寻找
if (hostToBind != null && hostToBind.length() > 0 && isInvalidLocalHost(hostToBind)) {
throw new IllegalArgumentException("Specified invalid bind ip from property:" + Constants.DUBBO_IP_TO_BIND + ", value:" + hostToBind);
}
if (hostToBind == null || hostToBind.length() == 0) {
hostToBind = protocolConfig.getHost(); // 从协议配置中获取
if (provider != null && (hostToBind == null || hostToBind.length() == 0)) {
// 到这里没有找到则再次尝试从provider配置中获取
hostToBind = provider.getHost();
}
if (isInvalidLocalHost(hostToBind)) {
anyhost = true;
try {
// 如果到这里获取的ip为空或者非法，则尝试赋值为本地主机地址
hostToBind = InetAddress.getLocalHost().getHostAddress();
} catch (UnknownHostException e) {
logger.warn(e.getMessage(), e);
}
if (isInvalidLocalHost(hostToBind)) {
if (registryURLs != null && registryURLs.size() > 0) {
for (URL registryURL : registryURLs) {
try {
Socket socket = new Socket();
try {
SocketAddress addr = new InetSocketAddress(registryURL.getHost(), registryURL.getPort());
socket.connect(addr, 1000);
hostToBind = socket.getLocalAddress().getHostAddress();
break;
} finally {
try {
socket.close();
} catch (Throwable e) {
}
}
} catch (Exception e) {
logger.warn(e.getMessage(), e);
}
}
}
if (isInvalidLocalHost(hostToBind)) {
// 如果到这里获取的ip还是为空或者非法，则尝试从本地网卡查找第一个有效的IP，如果没有获取到，则赋值为127.0.0.1
hostToBind = getLocalHost();
}
}
}
}
map.put(Constants.BIND_IP_KEY, hostToBind);
// 尝试从系统属性中获取注册中心ip配置
String hostToRegistry = getValueFromConfig(protocolConfig, Constants.DUBBO_IP_TO_REGISTRY);
if (hostToRegistry != null && hostToRegistry.length() > 0 && isInvalidLocalHost(hostToRegistry)) {
throw new IllegalArgumentException("Specified invalid registry ip from property:" + Constants.DUBBO_IP_TO_REGISTRY + ", value:" + hostToRegistry);
} else if (hostToRegistry == null || hostToRegistry.length() == 0) {
// 没有从系统环境中获取到则赋值为绑定的ip
hostToRegistry = hostToBind;
}
map.put(Constants.ANYHOST_KEY, String.valueOf(anyhost));
return hostToRegistry;
}
ServiceConfig：
private Integer findConfigedPorts(ProtocolConfig protocolConfig, String name, Map<String, String> map) {
Integer portToBind = null;
// 从系统环境中解析绑定的端口
String port = getValueFromConfig(protocolConfig, Constants.DUBBO_PORT_TO_BIND);
// 将端口转换成int类型并判断是否合法（在0-65535范围之内）
portToBind = parsePort(port);
// 如果没有找到绑定端口的配置，继续寻找
if (portToBind == null) {
// 从protocol配置中寻找
portToBind = protocolConfig.getPort();
if (provider != null && (portToBind == null || portToBind == 0)) {
// 从provider配置中寻找
portToBind = provider.getPort();
}
// 默认protocol配置中寻找
final int defaultPort = ExtensionLoader.getExtensionLoader(Protocol.class).getExtension(name).getDefaultPort();
if (portToBind == null || portToBind == 0) {
portToBind = defaultPort;
}
if (portToBind == null || portToBind <= 0) {
// 获取随机端口，从缓存中获取，缓存中没有会返回Integer.MIN
portToBind = getRandomPort(name);
if (portToBind == null || portToBind < 0) {
// 获取可用端口
portToBind = getAvailablePort(defaultPort);
// 放入缓存
putRandomPort(name, portToBind);
}
logger.warn("Use random available port(" + portToBind + ") for protocol " + name);
}
}
map.put(Constants.BIND_PORT_KEY, String.valueOf(portToBind));
// 注册中心端口，默认情况下不用作绑定端口
String portToRegistryStr = getValueFromConfig(protocolConfig, Constants.DUBBO_PORT_TO_REGISTRY);
Integer portToRegistry = parsePort(portToRegistryStr);
if (portToRegistry == null) {
portToRegistry = portToBind;
}
return portToRegistry;
}
ServiceConfig：
private void exportLocal(URL url) {
// 判断协议是否不是injvm
if (!Constants.LOCAL_PROTOCOL.equalsIgnoreCase(url.getProtocol())) {
URL local = URL.valueOf(url.toFullString())
.setProtocol(Constants.LOCAL_PROTOCOL) // 设置injvm协议
.setHost(LOCALHOST) // 127.0.0.1
.setPort(0);
ServiceClassHolder.getInstance().pushServiceClass(getServiceClass(ref));
/* 获取invoker，暴露服务 */
Exporter<?> exporter = protocol.export(
proxyFactory.getInvoker(ref, (Class) interfaceClass, local));
exporters.add(exporter); // 添加到已暴露的服务列表中
logger.info("Export dubbo service " + interfaceClass.getName() + " to local registry");
}
}
在Dubbo源码解析之扩展点（ExtensionLoader）篇中，我们分析扩展点的实例化流程，这里将URL的protocol设置为injvm，所以这里的protocol为InjvmProtocol，并用ProtocolFilterWrapper和ProtocolListenerWrapper对protocol进行了包装（其他Protocol的扩展点如RegistryProtocol也同样会经过这两层包装）。
JavassistProxyFactory：
public <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) {
// 包装类无法处理类名包含$的类
final Wrapper wrapper = Wrapper.getWrapper(proxy.getClass().getName().indexOf('$') < 0 ? proxy.getClass() : type);
return new AbstractProxyInvoker<T>(proxy, type, url) {
@Override
protected Object doInvoke(T proxy, String methodName,
Class<?>[] parameterTypes,
Object[] arguments) throws Throwable {
return wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments);
}
};
}
export暴露流程首先会经过包装类的处理：
ProtocolFilterWrapper：
public <T> Exporter <T> export (Invoker <T> invoker) throws RpcException {
// RegistryProtocol忽略这层包装
if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
return protocol.export(invoker);
}
/* 构建Invoker调用链，调用下一个包装过程继续进行export */
return protocol.export(buildInvokerChain(invoker, Constants.SERVICE_FILTER_KEY, Constants.PROVIDER));
}
ProtocolFilterWrapper：
private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) {
Invoker<T> last = invoker;
// 获取所有自动激活的Filter
List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);
if (filters.size() > 0) {
for (int i = filters.size() - 1; i >= 0; i--) {
final Filter filter = filters.get(i);
final Invoker<T> next = last;
last = new Invoker<T>() {
public Class<T> getInterface() {
return invoker.getInterface();
}
public URL getUrl() {
return invoker.getUrl();
}
public boolean isAvailable() {
return invoker.isAvailable();
}
public Result invoke(Invocation invocation) throws RpcException {
// invoker调用时首先经过filter的过滤
return filter.invoke(next, invocation);
}
public void destroy() {
invoker.destroy();
}
@Override
public String toString() {
return invoker.toString();
}
};
}
}
return last;
}
这里的Filter有很多，EchoFilter、ClassLoaderFilter、GenericFIlter、ContextFilter、TraceFilter、TimeoutFilter、MonitorFilter、ExceptionFilter，功能不一一赘述，有兴趣的读者自行查看。接下来会经过下一个Protocol包装类：
ProtocolListenerWrapper：
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
// RegistryProtocol忽略本次包装
if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
return protocol.export(invoker);
}
/* 添加ExporterListener，暴露Invoker */
return new ListenerExporterWrapper<T>(protocol.export(invoker),
Collections.unmodifiableList(ExtensionLoader.getExtensionLoader(ExporterListener.class)
.getActivateExtension(invoker.getUrl(), Constants.EXPORTER_LISTENER_KEY)));
}
ExporterListener的作用是监听Exporter的export和unexport动作，dubbo本身没有具体实现，可以进行相应的扩展。接下来会真正的进入InjvmProtocol：
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
return new InjvmExporter<T>(invoker, invoker.getUrl().getServiceKey(), exporterMap);
}
InjvmExporter的作用比较简单，就是简单的在exporterMap中添加或删除key和自身Exporter的关系。本次服务暴露后，接下来是向注册中心暴露服务，URL的protocol设置为registry，所以这里的Protocol扩展点为RegistryProtocol，上面我们看到包装类都忽略了RegistryProtocol，直接来看RegistryProtocol的export实现：
RegistryProtocol：
public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
/* 暴露invoker */
final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);
// 从invoker中获取之前构建好的url
URL registryUrl = getRegistryUrl(originInvoker);
// 获取注册中心
final Registry registry = getRegistry(originInvoker);
// 获取已经注册的提供者的url
final URL registedProviderUrl = getRegistedProviderUrl(originInvoker);
// 判断是否延迟发布
boolean register = registedProviderUrl.getParameter("register", true);
// 将提供者注册到提供者消费者注册表中
ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registedProviderUrl);
if (register) {
// 注册提供者
register(registryUrl, registedProviderUrl);
// 将提供者消费者注册表的相关提供者设置为已注册
ProviderConsumerRegTable.getProviderWrapper(originInvoker).setReg(true);
}
// 获取订阅覆盖数据的url
final URL overrideSubscribeUrl = getSubscribedOverrideUrl(registedProviderUrl);
// 覆盖监听器
final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
// 订阅
registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
// 确保每次暴露都会返回一个新的实例
return new Exporter<T>() {
public Invoker<T> getInvoker() {
return exporter.getInvoker();
}
public void unexport() {
try {
exporter.unexport();
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
try {
registry.unregister(registedProviderUrl);
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
try {
overrideListeners.remove(overrideSubscribeUrl);
registry.unsubscribe(overrideSubscribeUrl, overrideSubscribeListener);
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
}
};
}
这里有关注册中心的获取、注册、订阅等相关操作，我们用单独的文章来分析，详见：传送门。
RegistryProtocol：
private <T> ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker) {
String key = getCacheKey(originInvoker); // 缓存key，就是providerUrl
// bounds为providerurl和exporter的映射，目的是为了解决RMI重复出现端口冲突的问题，已经暴露的服务不再暴露。
ExporterChangeableWrapper<T> exporter = (ExporterChangeableWrapper<T>) bounds.get(key);
if (exporter == null) {
synchronized (bounds) {
exporter = (ExporterChangeableWrapper<T>) bounds.get(key);
if (exporter == null) {
// invokerDelegete的URL protocol为dubbo
final Invoker<?> invokerDelegete = new InvokerDelegete<T>(originInvoker, getProviderUrl(originInvoker));
/* 暴露服务 */
exporter = new ExporterChangeableWrapper<T>((Exporter<T>) protocol.export(invokerDelegete), originInvoker);
bounds.put(key, exporter);
}
}
}
return exporter;
}
DubboProtocol：
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
URL url = invoker.getUrl();
String key = serviceKey(url); // 格式（分组/接口全称:服务版本:端口），接口和端口是一定存在的，分组和服务版本不一定
DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
exporterMap.put(key, exporter);
// 是否为调度事件暴露一个stub服务
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);
}
}
/* 开启服务 */
openServer(url);
optimizeSerialization(url); // 优化序列化
return exporter;
}
DubboProtocol：
private void openServer(URL url) {
String key = url.getAddress();
// 客户端可以暴露仅用于服务端调用的服务
boolean isServer = url.getParameter(Constants.IS_SERVER_KEY, true);
if (isServer) {
ExchangeServer server = serverMap.get(key);
if (server == null) {
/* 创建服务 */
serverMap.put(key, createServer(url));
} else {
// 服务端支持重置，与重写一起使用
server.reset(url);
}
}
}
DubboProtocol：
private ExchangeServer createServer(URL url) {
// 当服务器关闭时发送只读事件，默认为true
url = url.addParameterIfAbsent(Constants.CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString());
// 默认启用心跳
url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));
// server，默认为netty
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, DubboCodec.NAME);
ExchangeServer server;
try {
/* 绑定 */
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;
}
Exchangers：
public static ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
if (url == null) {
throw new IllegalArgumentException("url == null");
}
if (handler == null) {
throw new IllegalArgumentException("handler == null");
}
url = url.addParameterIfAbsent(Constants.CODEC_KEY, "exchange");
/* 获取exchanger（默认为HeaderExchanger），绑定 */
return getExchanger(url).bind(url, handler);
}
HeaderExchanger：
public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
/* 绑定，构建server */
return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler))));
}
Transporters：
public static Server bind(URL url, ChannelHandler... handlers) throws RemotingException {
if (url == null) {
throw new IllegalArgumentException("url == null");
}
if (handlers == null || handlers.length == 0) {
throw new IllegalArgumentException("handlers == null");
}
ChannelHandler handler;
if (handlers.length == 1) {
handler = handlers[0];
} else {
handler = new ChannelHandlerDispatcher(handlers);
}
/* 获取Transporter，绑定 */
return getTransporter().bind(url, handler);
}
NettyTransporter：
public Server bind(URL url, ChannelHandler listener) throws RemotingException {
/* 构建NettyServer */
return new NettyServer(url, listener);
}
NettyServer：
public NettyServer(URL url, ChannelHandler handler) throws RemotingException {
/* 为url设置线程名称，包装handler，调用父类构造方法初始化 */
super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
}
AbstractServer：
public AbstractServer(URL url, ChannelHandler handler) throws RemotingException {
super(url, handler);
localAddress = getUrl().toInetSocketAddress();
String bindIp = getUrl().getParameter(Constants.BIND_IP_KEY, getUrl().getHost()); // ip
int bindPort = getUrl().getParameter(Constants.BIND_PORT_KEY, getUrl().getPort()); // 端口
if (url.getParameter(Constants.ANYHOST_KEY, false) || NetUtils.isInvalidLocalHost(bindIp)) {
bindIp = NetUtils.ANYHOST;
}
bindAddress = new InetSocketAddress(bindIp, bindPort); // 绑定地址
this.accepts = url.getParameter(Constants.ACCEPTS_KEY, Constants.DEFAULT_ACCEPTS);
this.idleTimeout = url.getParameter(Constants.IDLE_TIMEOUT_KEY, Constants.DEFAULT_IDLE_TIMEOUT);
try {
doOpen(); /* 开启服务 */
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);
}
DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension();
executor = (ExecutorService) dataStore.get(Constants.EXECUTOR_SERVICE_COMPONENT_KEY, Integer.toString(url.getPort()));
}
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)); // worker线程池
ChannelFactory channelFactory = new NioServerSocketChannelFactory(boss, worker, getUrl().getPositiveParameter(Constants.IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS));
bootstrap = new ServerBootstrap(channelFactory);
final NettyHandler nettyHandler = new NettyHandler(getUrl(), this);
channels = nettyHandler.getChannels();
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
public ChannelPipeline getPipeline() {
NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyServer.this);
ChannelPipeline pipeline = Channels.pipeline();
// 解码器
pipeline.addLast("decoder", adapter.getDecoder());
// 编码器
pipeline.addLast("encoder", adapter.getEncoder());
// 处理器
pipeline.addLast("handler", nettyHandler);
return pipeline;
}
});
// 绑定
channel = bootstrap.bind(getBindAddress());
}
这我们看到了dubbo使用netty来开启服务，需要读者对netty的知识有一定的了解，这里使用的是netty3，dubbo目前已经有netty4的使用，在com.alibaba.dubbo.remoting.transport.netty4包下。这里我们要对handler的包装过程有清楚的认知，大致如下：
DubboProtocol.requestHandler --> DecodeHandler --> HeaderExchangeHandler --> MultiMessageHandler --> HeartbeatHandler --> AllChannelHandler --> NettyHandler
到这里，整个服务的暴露就完成了，我们是从本地服务暴露开始分析的，用了很大篇幅来讲解这个过程，远程服务暴露也是同样复用这个流程。