Dubbo——架构和原理

一、架构设计图

1、service 业务逻辑层：接口和接口实现，dubbo的服务提供端暴露哪个接口和接口的实现，dubbo的服务消费端订阅的服务接口，用户仅需要关注这一层
2、config 配置层：对外配置接口，以 ServiceConfig、ReferenceConfig 为中心，可以直接初始化配置类(@Bean的方式)，也可以通过 Spring 解析配置生成配置类
3、proxy 服务代理层：服务接口透明代理，生成服务的客户端 Stub 和服务器端 Skeleton，以 ServiceProxy 为中心，扩展接口为 ProxyFactory
4、registry 注册中心层：封装服务地址的注册与发现，以服务 URL 为中心，扩展接口为 RegistryFactory，Registry，RegistryService
5、cluster 路由层：封装多个提供者的路由及负载均衡，并桥接注册中心，以 Invoker 为中心，扩展接口为 Cluster、Directory、Router、LoadBalance
6、monitor 监控层：RPC 调用次数和调用时间监控，以 Statistics 为中心，扩展接口为 MonitorFactory、Monitor、MonitorService
7、protocol 远程调用层：封装 RPC 调用，以 Invocation、Result 为中心，扩展接口为 Protocol、Invoke、Exporter
8、exchange 信息交换层：封装请求响应模式，同步转异步，以 Request、Response 为中心，扩展接口为 Exchanger、ExchangeChannel、ExchangeClient、ExchangeServer
9、transport 网络传输层：抽象 mina 和 netty 为统一接口，以 Message 为中心，扩展接口为 Channel、Transporter、Client、Server、Codec
10、serialize 数据序列化层：可复用的一些工具，扩展接口为 Serialization、ObjectInput、ObjectOutput、ThreadPool

二、标签解析
Spring解析配置文件中的每一个标签都会有相应的类来完成，这些类都实现了同一个接口：BeanDefinitionParser

public abstract interface BeanDefinitionParser {
public abstract BeanDefinition parse(Element paramElement, ParserContext paramParserContext);
}

该接口的继承树如下：其中就有DubboBeanDefinitionParser用来解析配置文件中的dubbo标签

DubboBeanDefinitionParser的parse方法如下：可以看出来其实就是解析每一个标签的配置，并给相应的对象属性赋值

private static BeanDefinition parse(Element element, ParserContext parserContext, Class<?> beanClass,
boolean required) {
RootBeanDefinition beanDefinition = new RootBeanDefinition();
beanDefinition.setBeanClass(beanClass);
beanDefinition.setLazyInit(false);
String id = element.getAttribute("id");
if ((((id == null) || (id.length() == 0))) && (required)) {
String generatedBeanName = element.getAttribute("name");
if ((generatedBeanName == null) || (generatedBeanName.length() == 0)) {
if (ProtocolConfig.class.equals(beanClass))
generatedBeanName = "dubbo";
else {
generatedBeanName = element.getAttribute("interface");
}
}
if ((generatedBeanName == null) || (generatedBeanName.length() == 0)) {
generatedBeanName = beanClass.getName();
}
id = generatedBeanName;
int counter = 2;
while (parserContext.getRegistry().containsBeanDefinition(id)) {
id = generatedBeanName + (counter++);
}
}
if ((id != null) && (id.length() > 0)) {
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 = element.getAttribute("class");
if ((className != null) && (className.length() > 0)) {
RootBeanDefinition classDefinition = new RootBeanDefinition();
classDefinition.setBeanClass(ReflectUtils.forName(className));
classDefinition.setLazyInit(false);
parseProperties(element.getChildNodes(), classDefinition);
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 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)) {
continue;
}
Class type = setter.getParameterTypes()[0];
String property = StringUtils.camelToSplitName(name.substring(3, 4).toLowerCase() + name.substring(4), "-");
props.add(property);
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 localNoSuchMethodException1) {
}
}
if ((getter == null) || (!(Modifier.isPublic(getter.getModifiers()))))
continue;
if (!(type.equals(getter.getReturnType()))) {
continue;
}

if ("parameters".equals(property)) {
parameters = parseParameters(element.getChildNodes(), beanDefinition);
} 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 = element.getAttribute(property);
if (value != null) {
value = value.trim();
if (value.length() > 0) {
if (("registry".equals(property)) && ("N/A".equalsIgnoreCase(value))) {
RegistryConfig registryConfig = new RegistryConfig();
registryConfig.setAddress("N/A");
beanDefinition.getPropertyValues().addPropertyValue(property, registryConfig);
} else if (("registry".equals(property)) && (value.indexOf(44) != -1)) {
parseMultiRef("registries", value, beanDefinition, parserContext);
} else if (("provider".equals(property)) && (value.indexOf(44) != -1)) {
parseMultiRef("providers", value, beanDefinition, parserContext);
} else if (("protocol".equals(property)) && (value.indexOf(44) != -1)) {
parseMultiRef("protocols", value, beanDefinition, parserContext);
} else {
Object reference;
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)))) {
value = null;
}
reference = value;
} else {
Object reference;
if (("protocol".equals(property))
&& (ExtensionLoader.getExtensionLoader(Protocol.class).hasExtension(value))
&& (((!(parserContext.getRegistry().containsBeanDefinition(value)))
|| (!(ProtocolConfig.class.getName().equals(parserContext.getRegistry()
.getBeanDefinition(value).getBeanClassName())))))) {
if ("dubbo:provider".equals(element.getTagName())) {
logger.warn("Recommended replace <dubbo:provider protocol=\"" + value
+ "\" ... /> to <dubbo:protocol name=\"" + value + "\" ... />");
}

ProtocolConfig protocol = new ProtocolConfig();
protocol.setName(value);
reference = protocol;
} else if ("onreturn".equals(property)) {
int index = value.lastIndexOf(".");
String returnRef = value.substring(0, index);
String returnMethod = value.substring(index + 1);
Object reference = new RuntimeBeanReference(returnRef);
beanDefinition.getPropertyValues().addPropertyValue("onreturnMethod", returnMethod);
} else if ("onthrow".equals(property)) {
int index = value.lastIndexOf(".");
String throwRef = value.substring(0, index);
String throwMethod = value.substring(index + 1);
Object reference = new RuntimeBeanReference(throwRef);
beanDefinition.getPropertyValues().addPropertyValue("onthrowMethod", throwMethod);
} else if ("oninvoke".equals(property)) {
int index = value.lastIndexOf(".");
String invokeRef = value.substring(0, index);
String invokeRefMethod = value.substring(index + 1);
Object reference = new RuntimeBeanReference(invokeRef);
beanDefinition.getPropertyValues().addPropertyValue("oninvokeMethod",
invokeRefMethod);
} 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(property, 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