首先了解一下dubbo怎么解析自定义的标签的。
第一种：xml
在 dubbo-config 模块的 dubbo-config-spring 下面，找到resources下面的META-INF下面的spring.handlers文件，该文件主要是指定标签校验为本地实现类，该文件里面的内容也是以key、value存储的，key就是我们在xml里面必须要添加的schema头，value就是解析的类，然后再去定义一个xsd文件，通过我们的定义按照这个文件进行约束供我们进行实现。里面配置了一个DubboNamespaceHandler 类，该类实现于spring-framework下面的beans模块的 NamespaceHandlerSupport 抽象类，该抽象类又实现于 NamespaceHandler 接口，这个接口里面有一个init()方法，DubboNamespaceHandler 通过init()方法会把我们在xml里面配置的标签通过 DubboBeanDefinitionParser 给解析出来
在init()方法里面可以看到registerBeanDefinitionParser()方法的第一个参数就是我们在xml里面配置的<dubbo:xxx> 标签，然后把这些标签解析为 DubboBeanDefinitionParser 构造方法里面出入的class类型，比如第一个application，会把配置文件里面的<dubbo:application>转为 ApplicationConfig ,最后转为 BeanDefinition 能够让spring管理dubbo
public class DubboNamespaceHandler extends NamespaceHandlerSupport implements ConfigurableSourceBeanMetadataElement {
static {
Version.checkDuplicate(DubboNamespaceHandler.class);
}
@Override
public void init() {
registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
registerBeanDefinitionParser("config-center", new DubboBeanDefinitionParser(ConfigCenterBean.class, true));
registerBeanDefinitionParser("metadata-report", new DubboBeanDefinitionParser(MetadataReportConfig.class, true));
registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
registerBeanDefinitionParser("metrics", new DubboBeanDefinitionParser(MetricsConfig.class, true));
registerBeanDefinitionParser("ssl", new DubboBeanDefinitionParser(SslConfig.class, true));
registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
registerBeanDefinitionParser("annotation", new AnnotationBeanDefinitionParser());
}
......
}DubboBeanDefinitionParser 实现于 spring-framework的beans模块的 BeanDefinitionParser 接口，该接口有一个
BeanDefinition parse(Element element, ParserContext parserContext)方法，该方法主要是解析我们xml里面的标签。
在 DubboBeanDefinitionParser 接口的主要实现代码
@Override
public BeanDefinition parse(Element element, ParserContext parserContext) {
return parse(element, parserContext, beanClass, required);
}
@SuppressWarnings("unchecked")
private static RootBeanDefinition parse(Element element, ParserContext parserContext, Class<?> beanClass, boolean required) {
RootBeanDefinition beanDefinition = new RootBeanDefinition();
beanDefinition.setBeanClass(beanClass);
beanDefinition.setLazyInit(false);
String id = resolveAttribute(element, "id", parserContext);
if (StringUtils.isEmpty(id) && required) {
String generatedBeanName = resolveAttribute(element, "name", parserContext);
if (StringUtils.isEmpty(generatedBeanName)) {
if (ProtocolConfig.class.equals(beanClass)) {
generatedBeanName = "dubbo";
} else {
generatedBeanName = resolveAttribute(element, "interface", parserContext);
}
}
if (StringUtils.isEmpty(generatedBeanName)) {
generatedBeanName = beanClass.getName();
}
id = generatedBeanName;
int counter = 2;
while (parserContext.getRegistry().containsBeanDefinition(id)) {
id = generatedBeanName + (counter++);
}
}
if (StringUtils.isNotEmpty(id)) {
if (parserContext.getRegistry().containsBeanDefinition(id)) {
throw new IllegalStateException("Duplicate spring bean id " + id);
}
parserContext.getRegistry().registerBeanDefinition(id, beanDefinition);
beanDefinition.getPropertyValues().addPropertyValue("id", id);
}
if (ProtocolConfig.class.equals(beanClass)) {
for (String name : parserContext.getRegistry().getBeanDefinitionNames()) {
BeanDefinition definition = parserContext.getRegistry().getBeanDefinition(name);
PropertyValue property = definition.getPropertyValues().getPropertyValue("protocol");
if (property != null) {
Object value = property.getValue();
if (value instanceof ProtocolConfig && id.equals(((ProtocolConfig) value).getName())) {
definition.getPropertyValues().addPropertyValue("protocol", new RuntimeBeanReference(id));
}
}
}
} else if (ServiceBean.class.equals(beanClass)) {
String className = resolveAttribute(element, "class", parserContext);
if (StringUtils.isNotEmpty(className)) {
RootBeanDefinition classDefinition = new RootBeanDefinition();
classDefinition.setBeanClass(ReflectUtils.forName(className));
classDefinition.setLazyInit(false);
parseProperties(element.getChildNodes(), classDefinition, parserContext);
beanDefinition.getPropertyValues().addPropertyValue("ref", new BeanDefinitionHolder(classDefinition, id + "Impl"));
}
} else if (ProviderConfig.class.equals(beanClass)) {
parseNested(element, parserContext, ServiceBean.class, true, "service", "provider", id, beanDefinition);
} else if (ConsumerConfig.class.equals(beanClass)) {
parseNested(element, parserContext, ReferenceBean.class, false, "reference", "consumer", id, beanDefinition);
}
Set<String> props = new HashSet<>();
ManagedMap parameters = null;
for (Method setter : beanClass.getMethods()) {
String name = setter.getName();
if (name.length() > 3 && name.startsWith("set")
&& Modifier.isPublic(setter.getModifiers())
&& setter.getParameterTypes().length == 1) {
Class<?> type = setter.getParameterTypes()[0];
String beanProperty = name.substring(3, 4).toLowerCase() + name.substring(4);
String property = StringUtils.camelToSplitName(beanProperty, "-");
props.add(property);
// check the setter/getter whether match
Method getter = null;
try {
getter = beanClass.getMethod("get" + name.substring(3), new Class<?>[0]);
} catch (NoSuchMethodException e) {
try {
getter = beanClass.getMethod("is" + name.substring(3), new Class<?>[0]);
} catch (NoSuchMethodException e2) {
// ignore, there is no need any log here since some class implement the interface: EnvironmentAware,
// ApplicationAware, etc. They only have setter method, otherwise will cause the error log during application start up.
}
}
if (getter == null
|| !Modifier.isPublic(getter.getModifiers())
|| !type.equals(getter.getReturnType())) {
continue;
}
if ("parameters".equals(property)) {
parameters = parseParameters(element.getChildNodes(), beanDefinition, parserContext);
} else if ("methods".equals(property)) {
parseMethods(id, element.getChildNodes(), beanDefinition, parserContext);
} else if ("arguments".equals(property)) {
parseArguments(id, element.getChildNodes(), beanDefinition, parserContext);
} else {
String value = resolveAttribute(element, property, parserContext);
if (value != null) {
value = value.trim();
if (value.length() > 0) {
if ("registry".equals(property) && RegistryConfig.NO_AVAILABLE.equalsIgnoreCase(value)) {
RegistryConfig registryConfig = new RegistryConfig();
registryConfig.setAddress(RegistryConfig.NO_AVAILABLE);
beanDefinition.getPropertyValues().addPropertyValue(beanProperty, registryConfig);
} else if ("provider".equals(property) || "registry".equals(property) || ("protocol".equals(property) && AbstractServiceConfig.class.isAssignableFrom(beanClass))) {
/**
* For 'provider' 'protocol' 'registry', keep literal value (should be id/name) and set the value to 'registryIds' 'providerIds' protocolIds'
* The following process should make sure each id refers to the corresponding instance, here's how to find the instance for different use cases:
* 1. Spring, check existing bean by id, see{@link ServiceBean#afterPropertiesSet()}; then try to use id to find configs defined in remote Config Center
* 2. API, directly use id to find configs defined in remote Config Center; if all config instances are defined locally, please use {@link ServiceConfig#setRegistries(List)}
*/
beanDefinition.getPropertyValues().addPropertyValue(beanProperty + "Ids", value);
} else {
Object reference;
if (isPrimitive(type)) {
if ("async".equals(property) && "false".equals(value)
|| "timeout".equals(property) && "0".equals(value)
|| "delay".equals(property) && "0".equals(value)
|| "version".equals(property) && "0.0.0".equals(value)
|| "stat".equals(property) && "-1".equals(value)
|| "reliable".equals(property) && "false".equals(value)) {
// backward compatibility for the default value in old version's xsd
value = null;
}
reference = value;
} else if (ONRETURN.equals(property) || ONTHROW.equals(property) || ONINVOKE.equals(property)) {
int index = value.lastIndexOf(".");
String ref = value.substring(0, index);
String method = value.substring(index + 1);
reference = new RuntimeBeanReference(ref);
beanDefinition.getPropertyValues().addPropertyValue(property + METHOD, method);
} else {
if ("ref".equals(property) && parserContext.getRegistry().containsBeanDefinition(value)) {
BeanDefinition refBean = parserContext.getRegistry().getBeanDefinition(value);
if (!refBean.isSingleton()) {
throw new IllegalStateException("The exported service ref " + value + " must be singleton! Please set the " + value + " bean scope to singleton, eg: <bean id=\"" + value + "\" scope=\"singleton\" ...>");
}
}
reference = new RuntimeBeanReference(value);
}
beanDefinition.getPropertyValues().addPropertyValue(beanProperty, reference);
}
}
}
}
}
}
NamedNodeMap attributes = element.getAttributes();
int len = attributes.getLength();
for (int i = 0; i < len; i++) {
Node node = attributes.item(i);
String name = node.getLocalName();
if (!props.contains(name)) {
if (parameters == null) {
parameters = new ManagedMap();
}
String value = node.getNodeValue();
parameters.put(name, new TypedStringValue(value, String.class));
}
}
if (parameters != null) {
beanDefinition.getPropertyValues().addPropertyValue("parameters", parameters);
}
return beanDefinition;
}这里面的判断有兴趣的可以自行debug研究，再来看看Annotation是怎么实现的。
第二种：Annotation
通过 DubboComponentScan 注解，该注解spring的 @Import 注解导入了 DubboComponentScanRegistrar.class ，该注解实现于 ImportBeanDefinitionRegistrar 接口，springboot里面很多地方都是通过该接口进行扩展的，这里不做深入研究。
服务发布
再来看下上面提到过的init()方法，我们知道服务发布是通过 @Service 注解(该注解在2.7.7版本已被废弃，通过DubboService 取代)实现的，会把我们 @Service 注解配置的类或者<dubbo:service>标签配置的类转为ServiceBean
可以看到该类实现了五个接口
-
InitializingBean（执行初始化方法） -
DisposableBean（执行销毁方法） -
ApplicationContextAware（获取ApplicationContext上下文） -
ApplicationListener<ContextRefreshedEvent>（事件监听，2.7.7已去掉） -
BeanNameAware（获取当前的beanName） -
ApplicationEventPublisherAware（发布事件）
这五个接口都是spring的
在spring上下文加载的时候触发 ApplicationListener 接口的onApplicationEvent()方法监听，首先判断该服务是否发布过了，没有发布的话就调用export()方法。
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
if (!isExported() && !isUnexported()) {
if (logger.isInfoEnabled()) {
logger.info("The service ready on spring started. service: " + getInterface());
}
export();
}
}
@Override
public void export() {
// 这里调用父类
super.export();
// Publish ServiceBeanExportedEvent
publishExportEvent();
}再来看父类 ServiceConfig 的export()方法，
public synchronized void export() {
// 检查或更新配置，比如完善默认配置：端口号、协议
checkAndUpdateSubConfigs();
// 是否要发布服务，可通过@Service注解的export属性设置为fasle，就是不把该接口暴露出去，默认值为true
if (!shouldExport()) {
return;
}
// 是否延时发布，可通过@Service注解的delay属性设置，这里提供延时加载的功能可能是考虑到spring容器还没初始化就加载该类会出错
if (shouldDelay()) {
delayExportExecutor.schedule(this::doExport, getDelay(), TimeUnit.MILLISECONDS);
} else {
doExport();
}
}在通过doExport()方法调用doExportUrls()，首先加载我们配置的注册中心地址，通过URL来驱动
registry://ip:2181/org.apache.dubbo.registry.RegistryService/…
private void doExportUrls() {
List<URL> registryURLs = loadRegistries(true);
for (ProtocolConfig protocolConfig : protocols) {
String pathKey = URL.buildKey(getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), group, version);
ProviderModel providerModel = new ProviderModel(pathKey, ref, interfaceClass);
ApplicationModel.initProviderModel(pathKey, providerModel);
doExportUrlsFor1Protocol(protocolConfig, registryURLs);
}
}registries就是我们配置的注册中心的地址
然后会拼接上我们配置的dubbo应用名称、协议名、端口号等一系列参数。
然后判断如果是服务提供者并且当前地址里面的registry参数不为空的话就把当前地址添加到registryList注册中心集合里面。
遍历完再回到doExportUrls()方法里面，接着去遍历我们配置的协议规则，目前我们只配置dubbo这一种协议，然后去构建我们的服务接口
进入到doExportUrlsFor1Protocol()方法，先把之前构建好的参数封装到map里面，这个map里面最多可以有三十多个参数，因为有些没有配置，这里只显示了20个
然后通过把map变为一个URL，这个url就非常熟悉了，就是我们最终存放在zk的地址
dubbo://192.168.124.7:20880/com.tqz.dubbo.api.ISayHelloService?anyhost=true&application=springboot-dubbo-provider&bean.name=ServiceBean:com.tqz.dubbo.api.ISayHelloService&bind.ip=192.168.124.7&bind.port=20880&cluster=failsafe&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=com.tqz.dubbo.api.ISayHelloService&methods=sayHello&pid=73828&qos-enable=false®ister=true&release=2.7.2&side=provider&timeout=50000×tamp=1616175325378
这时候url已经组装好了，接下来就要进行服务的发布了。还是在doExportUrlsFor1Protocol()方法中，首先获取了一个服务发布的范围，这里一共分为两种，一种是在同一个jvm里面调用，没必要走远程通信会通过injvm://ip:port方式进行调用，另外一种是remote，也就是上面我们组装的url进行远程调用。如果我们配置了注册中心的地址，默认两种都会进行发布。这里我们假设是远程调用，遍历registryURLs，也就是我们之前的registry://ip:2181/org.apache.dubbo.registry.RegistryService/…
String scope = url.getParameter(SCOPE_KEY);
// don't export when none is configured
if (!SCOPE_NONE.equalsIgnoreCase(scope)) {
// 如果是本地发布
if (!SCOPE_REMOTE.equalsIgnoreCase(scope)) {
exportLocal(url);
}
// 如果是远程调用
if (!SCOPE_LOCAL.equalsIgnoreCase(scope)) {
if (!isOnlyInJvm() && logger.isInfoEnabled()) {
logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);
}
if (CollectionUtils.isNotEmpty(registryURLs)) {
for (URL registryURL : registryURLs) {
// registryURL等于：registry://ip:2181/org.apache.dubbo.registry.RegistryService/...
//if protocol is only injvm ,not register
if (LOCAL_PROTOCOL.equalsIgnoreCase(url.getProtocol())) {
continue;
}
url = url.addParameterIfAbsent(DYNAMIC_KEY, registryURL.getParameter(DYNAMIC_KEY));
URL monitorUrl = loadMonitor(registryURL);
if (monitorUrl != null) {
url = url.addParameterAndEncoded(MONITOR_KEY, monitorUrl.toFullString());
}
......
// For providers, this is used to enable custom proxy to generate invoker
String proxy = url.getParameter(PROXY_KEY);
if (StringUtils.isNotEmpty(proxy)) {
registryURL = registryURL.addParameter(PROXY_KEY, proxy);
}
Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString()));
DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
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);
}
/**
* @since 2.7.0
* ServiceData Store
*/
MetadataReportService metadataReportService = null;
if ((metadataReportService = getMetadataReportService()) != null) {
metadataReportService.publishProvider(url);
}
}
}
this.urls.add(url);上面的先不用关心，直接看
Exporter<?> exporter = protocol.export(wrapperInvoker)这行，这时候的protocol是成员属性
private static final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();自适应扩展点，之前分析过 Protocol 接口的export()方法和refer()方法都有 @Adaptive 注解，会根据代理生成字节码Protocol$Adaptive，回过头来再看下这个类。在我们上面的registryURLs是registry://ip:2181/org.apache.dubbo.registry.RegistryService/…，所以生成字节码类里面的export()方法里面的extName一定是registry
public class Protocol$Adaptive implements org.apache.dubbo.rpc.Protocol {
public void destroy() {
throw new UnsupportedOperationException("The method public abstract void org.apache.dubbo.rpc.Protocol.destroy() of interface org.apache.dubbo.rpc.Protocol is not adaptive method!");
}
public int getDefaultPort() {
throw new UnsupportedOperationException("The method public abstract int org.apache.dubbo.rpc.Protocol.getDefaultPort() of interface org.apache.dubbo.rpc.Protocol is not adaptive method!");
}
public org.apache.dubbo.rpc.Exporter export(org.apache.dubbo.rpc.Invoker arg0) throws org.apache.dubbo.rpc.RpcException {
if (arg0 == null) throw new IllegalArgumentException("org.apache.dubbo.rpc.Invoker argument == null");
if (arg0.getUrl() == null)
throw new IllegalArgumentException("org.apache.dubbo.rpc.Invoker argument getUrl() == null");
org.apache.dubbo.common.URL url = arg0.getUrl();
String extName = (url.getProtocol() == null ? "dubbo" : url.getProtocol());
if (extName == null)
throw new IllegalStateException("Failed to get extension (org.apache.dubbo.rpc.Protocol) name from url (" + url.toString() + ") use keys([protocol])");
// extName等于：registry
org.apache.dubbo.rpc.Protocol extension = (org.apache.dubbo.rpc.Protocol) ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.Protocol.class).getExtension(extName);
return extension.export(arg0);
}
public org.apache.dubbo.rpc.Invoker refer(java.lang.Class arg0, org.apache.dubbo.common.URL arg1) throws org.apache.dubbo.rpc.RpcException {
if (arg1 == null) throw new IllegalArgumentException("url == null");
org.apache.dubbo.common.URL url = arg1;
String extName = (url.getProtocol() == null ? "dubbo" : url.getProtocol());
if (extName == null)
throw new IllegalStateException("Failed to get extension (org.apache.dubbo.rpc.Protocol) name from url (" + url.toString() + ") use keys([protocol])");
org.apache.dubbo.rpc.Protocol extension = (org.apache.dubbo.rpc.Protocol) ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.Protocol.class).getExtension(extName);
return extension.refer(arg0, arg1);
}
}在去dubbo的META-INF里面看下org.apache.dubbo.rpc.Protocol文件，在里面可以找到一个key为registry的，所以exprot()方法里面最后的extension应该等于 RegistryProtocol
进入到 RegistryProtocol 的export()方法，首先获取了注册中心的地址和服务提供者的地址
@Override
public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
URL registryUrl = getRegistryUrl(originInvoker);
// url to export locally
URL providerUrl = getProviderUrl(originInvoker);
// Subscribe the override data
// FIXME When the provider subscribes, it will affect the scene : a certain JVM exposes the service and call
// the same service. Because the subscribed is cached key with the name of the service, it causes the
// subscription information to cover.
// 服务更改进行重新，比如在控制台进行了更改
final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl);
final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
//export invoker
// 启动一个Netty服务
final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl);
// url to registry
final Registry registry = getRegistry(originInvoker);
final URL registeredProviderUrl = getRegisteredProviderUrl(providerUrl, registryUrl);
ProviderInvokerWrapper<T> providerInvokerWrapper = ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registeredProviderUrl);
//to judge if we need to delay publish
boolean register = registeredProviderUrl.getParameter("register", true);
if (register) {
register(registryUrl, registeredProviderUrl);
providerInvokerWrapper.setReg(true);
}
// Deprecated! Subscribe to override rules in 2.6.x or before.
registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
exporter.setRegisterUrl(registeredProviderUrl);
exporter.setSubscribeUrl(overrideSubscribeUrl);
//Ensure that a new exporter instance is returned every time export
return new DestroyableExporter<>(exporter);
}接下来我们看看是怎么启动的，在doLocalExport()方法里，bounds就是一个 ConcurrentHashMap，这里使用了jdk1.8特性，判断当前的key是否存在，就如不存在就put到该map中，然后通过protocol.export()方法暴露出去。这里的protocol会经过层层的包装，
- QosProtocolWrapper(ProtocolListenerWrapper(ProtocolFilterWrapper(DubboProtocol)))
最终也就是我们配置的dubbo协议
@SuppressWarnings("unchecked")
private <T> ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker, URL providerUrl) {
String key = getCacheKey(originInvoker);
return (ExporterChangeableWrapper<T>) bounds.computeIfAbsent(key, s -> {
Invoker<?> invokerDelegate = new InvokerDelegate<>(originInvoker, providerUrl);
return new ExporterChangeableWrapper<>((Exporter<T>) protocol.export(invokerDelegate), originInvoker);
});
}该方法前面的都不用关心，直接看最后两行，首先开启一个服务，暴露我们配置的20880协议，然后优化序列化
@Override
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
URL url = invoker.getUrl();
// export service.
String key = serviceKey(url);
DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
exporterMap.put(key, exporter);
//export an stub service for dispatching event
Boolean isStubSupportEvent = url.getParameter(STUB_EVENT_KEY, DEFAULT_STUB_EVENT);
Boolean isCallbackservice = url.getParameter(IS_CALLBACK_SERVICE, false);
if (isStubSupportEvent && !isCallbackservice) {
String stubServiceMethods = url.getParameter(STUB_EVENT_METHODS_KEY);
if (stubServiceMethods == null || stubServiceMethods.length() == 0) {
if (logger.isWarnEnabled()) {
logger.warn(new IllegalStateException("consumer [" + url.getParameter(INTERFACE_KEY) +
"], has set stubproxy support event ,but no stub methods founded."));
}
} else {
stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
}
}
openServer(url);
optimizeSerialization(url);
return exporter;
}在openServer里面会调用createServer()方法，默认开启server关闭时发送readonly事件，以及心跳机制事件，DEFAULT_REMOTING_SERVER的默认值是netty，还有其他的例如：mina、grizzy。
private ExchangeServer createServer(URL url) {
url = URLBuilder.from(url)
// send readonly event when server closes, it's enabled by default
.addParameterIfAbsent(CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString())
// enable heartbeat by default
.addParameterIfAbsent(HEARTBEAT_KEY, String.valueOf(DEFAULT_HEARTBEAT))
.addParameter(CODEC_KEY, DubboCodec.NAME)
.build();
String str = url.getParameter(SERVER_KEY, DEFAULT_REMOTING_SERVER);
if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
throw new RpcException("Unsupported server type: " + str + ", url: " + url);
}
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(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;
}然后通过 Exchangers.bind(url, requestHandler) ->
org.apache.dubbo.remoting.exchange.support.header.HeaderExchanger#bind ->
org.apache.dubbo.remoting.Transporters#bind(org.apache.dubbo.common.URL, org.apache.dubbo.remoting.ChannelHandler...) ->
org.apache.dubbo.remoting.transport.netty4.NettyTransporter#bind
进入到该方法，会初始化 NettyServer
@Override
public Server bind(URL url, ChannelHandler listener) throws RemotingException {
return new NettyServer(url, listener);
}public NettyServer(URL url, ChannelHandler handler) throws RemotingException {
super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
}调用父类的构造方法，然后调用doOpen()方法，该方法为抽象方法，由刚刚的实现类 NettyServer 去实现
public AbstractServer(URL url, ChannelHandler handler) throws RemotingException {
......
try {
doOpen();
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);
}
......
}由刚刚的实现类 NettyServer 去实现，到这里就把服务给暴露出去了。
@Override
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));
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());
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();
}回过头来看看服务发布做了哪些事情
- 基于spirng进行解析配置文件存储到config
- 各种判断逻辑，保证配置信息安全性
- 组装url：registry:// -> zookeeper:// -> dubbo:// -> injvm
- 构建一个Invoker（代理）
- RegistryProtocol.export()
- 各种包装（qos/filter/lisenter）
- DubboProtocol.export()发布服务
- 启动一个NettyServer#doOpen()
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