版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/rubulai/article/details/84996876
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 == 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;
}
在标签的解析进入DubboBeanDefinitionParser的parse方法之前会先通过DubboNamespaceHandler的init初始化方法：在该方法中会先将所有的dubbo标签类型放在一个HashMap中(key为标签名，value为对应的标签解析对象)，会将标签封装成对应的组件，这样在解析到这个标签时也就知道这个标签对应的是哪个类了。Spring的标签解析是逐个解析的，并不是在将配置文件一次性读完之后，一次性解析，而是读一个标签解析一个标签，因此dubbo的配置也可以参杂在Spring的bean配置文件中，效果是一样的，只不过单拉出来一个配置文件显得更规整
public class DubboNamespaceHandler extends NamespaceHandlerSupport {
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("monitor", new DubboBeanDefinitionParser(MonitorConfig.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());
}
static {
Version.checkDuplicate(DubboNamespaceHandler.class);
}
}
可以看到在解析到service和reference时并不是对应一个配置类(XxxConfig)，而是一个Bean：
registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
三、服务暴露流程
在将标签封装为组件的时候，如果标签是service则会将该标签封装为ServiceBean，这个ServiceBean的源码如下：实现了InitializingBean和ApplicationListener两个接口，这两个接口的实现方法是afterPropertiesSet和onApplicationEvent
public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean,
ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, BeanNameAware {
// ...
public void onApplicationEvent(ContextRefreshedEvent event) {
if ((isDelay()) && (!(isExported())) && (!(isUnexported()))) {
if (logger.isInfoEnabled()) {
logger.info("The service ready on spring started. service: " + getInterface());
}
export();
}
}
//...
public void afterPropertiesSet() throws Exception {
if (getProvider() == null) {
Map providerConfigMap = (this.applicationContext == null) ? null
: BeanFactoryUtils.beansOfTypeIncludingAncestors(this.applicationContext, ProviderConfig.class,
false, false);
if ((providerConfigMap != null) && (providerConfigMap.size() > 0)) {
Map protocolConfigMap = (this.applicationContext == null) ? null
: BeanFactoryUtils.beansOfTypeIncludingAncestors(this.applicationContext, ProtocolConfig.class,
false, false);
if ((((protocolConfigMap == null) || (protocolConfigMap.size() == 0)))
&& (providerConfigMap.size() > 1)) {
List providerConfigs = new ArrayList();
for (ProviderConfig config : providerConfigMap.values()) {
if ((config.isDefault() != null) && (config.isDefault().booleanValue())) {
providerConfigs.add(config);
}
}
if (!(providerConfigs.isEmpty()))
setProviders(providerConfigs);
} else {
ProviderConfig providerConfig = null;
for (ProviderConfig config : providerConfigMap.values()) {
if ((config.isDefault() == null) || (config.isDefault().booleanValue())) {
if (providerConfig != null) {
throw new IllegalStateException(
"Duplicate provider configs: " + providerConfig + " and " + config);
}
providerConfig = config;
}
}
if (providerConfig != null) {
setProvider(providerConfig);
}
}
}
}
if ((getApplication() == null) && (((getProvider() == null) || (getProvider().getApplication() == null)))) {
Map applicationConfigMap = (this.applicationContext == null) ? null
: BeanFactoryUtils.beansOfTypeIncludingAncestors(this.applicationContext, ApplicationConfig.class,
false, false);
if ((applicationConfigMap != null) && (applicationConfigMap.size() > 0)) {
ApplicationConfig applicationConfig = null;
for (ApplicationConfig config : applicationConfigMap.values()) {
if ((config.isDefault() == null) || (config.isDefault().booleanValue())) {
if (applicationConfig != null) {
throw new IllegalStateException(
"Duplicate application configs: " + applicationConfig + " and " + config);
}
applicationConfig = config;
}
}
if (applicationConfig != null) {
setApplication(applicationConfig);
}
}
}
if ((getModule() == null) && (((getProvider() == null) || (getProvider().getModule() == null)))) {
Map moduleConfigMap = (this.applicationContext == null) ? null
: BeanFactoryUtils.beansOfTypeIncludingAncestors(this.applicationContext, ModuleConfig.class, false,
false);
if ((moduleConfigMap != null) && (moduleConfigMap.size() > 0)) {
ModuleConfig moduleConfig = null;
for (ModuleConfig config : moduleConfigMap.values()) {
if ((config.isDefault() == null) || (config.isDefault().booleanValue())) {
if (moduleConfig != null) {
throw new IllegalStateException(
"Duplicate module configs: " + moduleConfig + " and " + config);
}
moduleConfig = config;
}
}
if (moduleConfig != null) {
setModule(moduleConfig);
}
}
}
if ((((getRegistries() == null) || (getRegistries().isEmpty())))
&& (((getProvider() == null) || (getProvider().getRegistries() == null)
|| (getProvider().getRegistries().isEmpty())))
&& (((getApplication() == null) || (getApplication().getRegistries() == null)
|| (getApplication().getRegistries().isEmpty())))) {
Map registryConfigMap = (this.applicationContext == null) ? null
: BeanFactoryUtils.beansOfTypeIncludingAncestors(this.applicationContext, RegistryConfig.class,
false, false);
if ((registryConfigMap != null) && (registryConfigMap.size() > 0)) {
List registryConfigs = new ArrayList();
for (RegistryConfig config : registryConfigMap.values()) {
if ((config.isDefault() == null) || (config.isDefault().booleanValue())) {
registryConfigs.add(config);
}
}
if ((registryConfigs != null) && (!(registryConfigs.isEmpty()))) {
super.setRegistries(registryConfigs);
}
}
}
if ((getMonitor() == null) && (((getProvider() == null) || (getProvider().getMonitor() == null)))
&& (((getApplication() == null) || (getApplication().getMonitor() == null)))) {
Map monitorConfigMap = (this.applicationContext == null) ? null
: BeanFactoryUtils.beansOfTypeIncludingAncestors(this.applicationContext, MonitorConfig.class,
false, false);
if ((monitorConfigMap != null) && (monitorConfigMap.size() > 0)) {
MonitorConfig monitorConfig = null;
for (MonitorConfig config : monitorConfigMap.values()) {
if ((config.isDefault() == null) || (config.isDefault().booleanValue())) {
if (monitorConfig != null) {
throw new IllegalStateException(
"Duplicate monitor configs: " + monitorConfig + " and " + config);
}
monitorConfig = config;
}
}
if (monitorConfig != null) {
setMonitor(monitorConfig);
}
}
}
if ((((getProtocols() == null) || (getProtocols().isEmpty()))) && (((getProvider() == null)
|| (getProvider().getProtocols() == null) || (getProvider().getProtocols().isEmpty())))) {
Map protocolConfigMap = (this.applicationContext == null) ? null
: BeanFactoryUtils.beansOfTypeIncludingAncestors(this.applicationContext, ProtocolConfig.class,
false, false);
if ((protocolConfigMap != null) && (protocolConfigMap.size() > 0)) {
List protocolConfigs = new ArrayList();
for (ProtocolConfig config : protocolConfigMap.values()) {
if ((config.isDefault() == null) || (config.isDefault().booleanValue())) {
protocolConfigs.add(config);
}
}
if ((protocolConfigs != null) && (!(protocolConfigs.isEmpty()))) {
super.setProtocols(protocolConfigs);
}
}
}
if ((((getPath() == null) || (getPath().length() == 0))) && (this.beanName != null)
&& (this.beanName.length() > 0) && (getInterface() != null) && (getInterface().length() > 0)
&& (this.beanName.startsWith(getInterface()))) {
setPath(this.beanName);
}
if (!(isDelay()))
export();
}
//...
}
在afterPropertiesSet()中会将标签中的配置信息保存起来，在onApplicationEvent()中调用export()暴露服务，具体的服务暴露流程参看下图：
四、服务引用流程
此处说的服务引用是说在消费者端的Controller或者Service组件中通过@Autowired注入Dubbo的组件，我们知道在服务的消费者端是没有服务接口的实现的，那服务对象时怎么注入成功的呢，其实注入的是一个代理对象，原理如下：
在将标签封装为组件的时候，如果标签是reference则会将该标签封装为ReferenceBean，这个ReferenceBean的源码如下：实现了FactoryBean接口，是一个工厂Bean
public class ReferenceBean<T> extends ReferenceConfig<T>
implements FactoryBean, ApplicationContextAware, InitializingBean, DisposableBean {
private static final long serialVersionUID = 213195494150089726L;
private transient ApplicationContext applicationContext;
//...
public Object getObject() throws Exception {
return get();
}
public Class<?> getObjectType() {
return getInterfaceClass();
}
@Parameter(excluded = true)
public boolean isSingleton() {
return true;
}
//...
}
由于ReferenceBean实现了FactoryBean接口，因此在获取该Bean的实例时会调用getObject()，在该方法中会调用get()，之后会调用createProxy()创建代理，具体的服务引用流程如下图：
五、服务调用流程
通过代理对象，在调用的过程中有容错、负载均衡、超时、失败重试等机制