We can see that when Dubbo container spring is started, the spring context is started. At this time, it will parse the bean configuration file of spring. The specific parsing work is done by Dubbo config spring. We can see that the corresponding classes are referenced in the Dubbo demo provider project.
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:dubbo="http://code.alibabatech.com/schema/dubbo" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd "> <!-- Provider application information for dependency calculation --> <dubbo:applicationname="hello-world-app" /> <!-- Use zookeeper Broadcast registry exposure service address --> <dubbo:registryprotocol="zookeeper" address="127.0.0.1:2181" /> <!-- use dubbo Protocol exposes service on port 20880 --> <dubbo:protocol name="dubbo"port="20880" /> <dubbo:monitorprotocol="registry"></dubbo:monitor> <!-- Declare the service interface to be exposed --> <dubbo:serviceinterface="demo.service.DemoService" ref="demoService"/> <!-- And local bean Same implementation services --> <bean id="demoService"class="demo.service.DemoServiceImpl" /> </beans>
There's one thing that hasn't been found here, that is, how does spring read the corresponding configuration file under Dubbo config spring? My personal guess is that spring will scan the META-INF folder under each jar to see if there are two files spring.handlers and spring.schemas.
In Dubbo, first register parsers with com.alibaba.dubbo.config.spring.schema.NamespaceHandler. When spring parses xml configuration files, these parsers will be called to generate corresponding BeanDefinition for spring management:
public class DubboNamespaceHandler extends NamespaceHandlerSupport { static { Version.checkDuplicate(DubboNamespaceHandler.class); } public void init() { //Configure < Dubbo: Application > tag resolver registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true)); //Configure the < Dubbo: module > tag parser registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true)); //Configure the < Dubbo: Registry > tag parser registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true)); //Configure the < Dubbo: monitor > tag parser registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true)); //Configure the < Dubbo: provider > tag resolver registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true)); //Configure the < Dubbo: consumer > tag parser registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true)); //Configure the < Dubbo: Protocol > tag parser registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true)); //Configure < Dubbo: Service > tag resolver registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true)); //Configure the < Dubbo: renewal > tag resolver registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false)); //Configure < Dubbo: annotation > tag resolver registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true)); } }
From here, we can see that there are not many supported tags. All parsers are encapsulated in dubbobean definition Parser. The corresponding class is the incoming beanClass. For example, the application is ApplicationConfig. module is ModuleConfig. After the Parser transformation, the provider.xml may look like the following (specific parsing will not be explained)
<bean id="hello-world-app" class="com.alibaba.dubbo.config.ApplicationConfig"/> <bean id="registryConfig" class="com.alibaba.dubbo.config.RegistryConfig"> <property name="address" value="10.125.195.174:2181"/> <property name="protocol" value="zookeeper"/> </bean> <bean id="dubbo" class="com.alibaba.dubbo.config.ProtocolConfig"> <property name="port" value="20880"/> </bean> <bean id="demo.service.DemoService" class="com.alibaba.dubbo.config.spring.ServiceBean"> <property name="interface" value="demo.service.DemoService"/> <property name="ref" ref="demoService"/> </bean> <bean id="demoService" class="demo.service.DemoServiceImpl" />
To summarize:
ApplicationConfig, RegistryConfig, and ProtocolConfig are just ordinary POJOs. Responsible for receiving data.
The real processing logic is in ServiceBean. See the code for details:
public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean, ApplicationContextAware, ApplicationListener, BeanNameAware { private static final long serialVersionUID = 213195494150089726L; private static transient ApplicationContext SPRING_CONTEXT; private transient ApplicationContext applicationContext; private transient String beanName; private transient boolean supportedApplicationListener; public ServiceBean() { super(); } public ServiceBean(Service service) { super(service); } public static ApplicationContext getSpringContext() { return SPRING_CONTEXT; } //Set the corresponding applicationConext public void setApplicationContext(ApplicationContext applicationContext) { this.applicationContext = applicationContext; SpringExtensionFactory.addApplicationContext(applicationContext); if (applicationContext != null) { SPRING_CONTEXT = applicationContext; try { Method method = applicationContext.getClass().getMethod("addApplicationListener", new Class<?>[]{ApplicationListener.class}); // Compatible with spring 2.0.1 method.invoke(applicationContext, new Object[] {this}); supportedApplicationListener = true; } catch (Throwable t) { if (applicationContext instanceof AbstractApplicationContext) { try { Method method = AbstractApplicationContext.class.getDeclaredMethod("addListener", new Class<?>[]{ApplicationListener.class}); // Compatible with spring 2.0.1 if (! method.isAccessible()) { method.setAccessible(true); } method.invoke(applicationContext, new Object[] {this}); supportedApplicationListener = true; } catch (Throwable t2) { } } } } } public void setBeanName(String name) { this.beanName = name; } public void onApplicationEvent(ApplicationEvent event) { //If the current provider has not exported after the container is loaded, call the export method once (this is for the case of delayed export) if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) { if (isDelay() && ! isExported() && ! isUnexported()) { if (logger.isInfoEnabled()) { logger.info("The service ready on spring started. service: " + getInterface()); } export(); } } } //Delay export or not private boolean isDelay() { Integer delay = getDelay(); ProviderConfig provider = getProvider(); if (delay == null && provider != null) { delay = provider.getDelay(); } return supportedApplicationListener && (delay == null || delay.intValue() == -1); } @SuppressWarnings({ "unchecked", "deprecation" }) public void afterPropertiesSet() throws Exception { //The provider here is actually the ProviderConfig object. If the provider is empty, spring has not initialized the ProtocolConfig bean when it creates the current bean. This is to make a front and back order guarantee if (getProvider() == null) { Map<String, ProviderConfig> providerConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProviderConfig.class, false, false); if (providerConfigMap != null && providerConfigMap.size() > 0) { Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false); if ((protocolConfigMap == null || protocolConfigMap.size() == 0) && providerConfigMap.size() > 1) { // Compatible with older versions List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>(); for (ProviderConfig config : providerConfigMap.values()) { if (config.isDefault() != null && config.isDefault().booleanValue()) { providerConfigs.add(config); } } if (providerConfigs.size() > 0) { 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); } } } } //As above, create the ApplicationConfig bean manually if (getApplication() == null && (getProvider() == null || getProvider().getApplication() == null)) { Map<String, ApplicationConfig> applicationConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(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 no module is created, manually create the module. In the HelloWorld example, module is not used. if (getModule() == null && (getProvider() == null || getProvider().getModule() == null)) { Map<String, ModuleConfig> moduleConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(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); } } } //Initialize registry if ((getRegistries() == null || getRegistries().size() == 0) && (getProvider() == null || getProvider().getRegistries() == null || getProvider().getRegistries().size() == 0) && (getApplication() == null || getApplication().getRegistries() == null || getApplication().getRegistries().size() == 0)) { Map<String, RegistryConfig> registryConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, RegistryConfig.class, false, false); if (registryConfigMap != null && registryConfigMap.size() > 0) { List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>(); for (RegistryConfig config : registryConfigMap.values()) { if (config.isDefault() == null || config.isDefault().booleanValue()) { registryConfigs.add(config); } } if (registryConfigs != null && registryConfigs.size() > 0) { super.setRegistries(registryConfigs); } } } //Initialize monitor (not used in HelloWorld example) if (getMonitor() == null && (getProvider() == null || getProvider().getMonitor() == null) && (getApplication() == null || getApplication().getMonitor() == null)) { Map<String, MonitorConfig> monitorConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(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); } } } //Initialize protocol if ((getProtocols() == null || getProtocols().size() == 0) && (getProvider() == null || getProvider().getProtocols() == null || getProvider().getProtocols().size() == 0)) { Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false); if (protocolConfigMap != null && protocolConfigMap.size() > 0) { List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>(); for (ProtocolConfig config : protocolConfigMap.values()) { if (config.isDefault() == null || config.isDefault().booleanValue()) { protocolConfigs.add(config); } } if (protocolConfigs != null && protocolConfigs.size() > 0) { super.setProtocols(protocolConfigs); } } } //Set the service name. if (getPath() == null || getPath().length() == 0) { if (beanName != null && beanName.length() > 0 && getInterface() != null && getInterface().length() > 0 && beanName.startsWith(getInterface())) { setPath(beanName); } } //Call export if (! isDelay()) { export(); } } //Call unexport public void destroy() throws Exception { unexport(); } }
Some comments have been added to the code. Although it's long, the logic is simple. Many features of spring are used.