Dubbo 服务启动初始化注解实现源码分析
Dubbo的版本2.7.x，SpringBoot整合
概要
Dubbo 注解配置是基于 Spring 注解配置 的，巧妙地利用 Spring 进行配置简化。建议同学们优先去了解Spring 注解配置后阅读。
@EnableDubbo @EnableDubboConfig @DubboComponentScan 这三个注解位于 dubbo-config 模块的 dubbo-config-spring 项目下的 org.apache.dubbo.config.spring.context.annotation 包中，是主要的初始化配置注解。
@DubboService @DubboReference这二个注解位于 dubbo-common 模块的 dubbo-common 项目下的 org.apache.dubbo.config.annotation 包中，基于 @DubboComponentScan 扫描实现了初始化。
@EnableDubbo
@EnableDubbo 注解并未提供多余的功能仅是将 @DubboComponentScan 和 @EnableDubboConfig 组合起来方便用户使用，简单的看下代码。
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
@EnableDubboConfig
@DubboComponentScan
public @interface EnableDubbo {
@AliasFor(annotation = DubboComponentScan.class, attribute = "basePackages")
String[] scanBasePackages() default {};
@AliasFor(annotation = DubboComponentScan.class, attribute = "basePackageClasses")
Class<?>[] scanBasePackageClasses() default {};
@AliasFor(annotation = EnableDubboConfig.class, attribute = "multiple")
boolean multipleConfig() default true;
}
@EnableDubboConfig
@EnableDubboConfig 注解的目的就是帮我们简化这些(ApplicationConfig、ModuleConfig、RegistryConfig、ProtocolConfig、MonitorConfig、ProviderConfig、ConsumerConfig 等)配置，只要将相应的配置项通过 .properties 文件交由 @PropertySource 注解由 Spring 加载到 Environment 中，Dubbo 即可通过 Environment 中相应的属性与 ApplicationConfig 对象同名的属性进行绑定，而这个过程都是自动的。本身代码中作者给出了注释，问题变得显而易见。
/**
* As a convenient and multiple {@link EnableDubboConfigBinding}
* in default behavior , is equal to single bean bindings with below convention prefixes of properties:
* <ul>
* <li>{@link ApplicationConfig} binding to property : "dubbo.application"</li>
* <li>{@link ModuleConfig} binding to property : "dubbo.module"</li>
* <li>{@link RegistryConfig} binding to property : "dubbo.registry"</li>
* <li>{@link ProtocolConfig} binding to property : "dubbo.protocol"</li>
* <li>{@link MonitorConfig} binding to property : "dubbo.monitor"</li>
* <li>{@link ProviderConfig} binding to property : "dubbo.provider"</li>
* <li>{@link ConsumerConfig} binding to property : "dubbo.consumer"</li>
* </ul>
* <p>
* In contrast, on multiple bean bindings that requires to set {@link #multiple()} to be <code>true</code> :
* <ul>
* <li>{@link ApplicationConfig} binding to property : "dubbo.applications"</li>
* <li>{@link ModuleConfig} binding to property : "dubbo.modules"</li>
* <li>{@link RegistryConfig} binding to property : "dubbo.registries"</li>
* <li>{@link ProtocolConfig} binding to property : "dubbo.protocols"</li>
* <li>{@link MonitorConfig} binding to property : "dubbo.monitors"</li>
* <li>{@link ProviderConfig} binding to property : "dubbo.providers"</li>
* <li>{@link ConsumerConfig} binding to property : "dubbo.consumers"</li>
* </ul>
*
* @see EnableDubboConfigBinding
* @see DubboConfigConfiguration
* @see DubboConfigConfigurationRegistrar
* @since 2.5.8
*/
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
@Import(DubboConfigConfigurationRegistrar.class)
public @interface EnableDubboConfig {
boolean multiple() default true;
}
DubboConfigConfigurationRegistrar
@EnableDubboConfig 背后的注册处理就是通过这个(@Import(DubboConfigConfigurationRegistrar.class)完成的，DubboConfigConfigurationRegistrar 继承实现于 Spring 提供的一个接口 ImportBeanDefinitionRegistrar，这个类会在 Spring 中注册两个对象 DubboConfigConfiguration.Single 和 DubboConfigConfiguration.Multiple，区分同一属性的单个配置和多个配置。
package org.springframework.context.annotation;
public interface ImportBeanDefinitionRegistrar {
void registerBeanDefinitions(AnnotationMetadata var1, BeanDefinitionRegistry var2);
}
public class DubboConfigConfigurationRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
AnnotationAttributes attributes = AnnotationAttributes.fromMap(
importingClassMetadata.getAnnotationAttributes(EnableDubboConfig.class.getName()));
boolean multiple = attributes.getBoolean("multiple");
registerBeans(registry, DubboConfigConfiguration.Single.class);
if (multiple) {
registerBeans(registry, DubboConfigConfiguration.Multiple.class);
}
registerCommonBeans(registry);
}
}
DubboConfigConfiguration
查看 DubboConfigConfiguration 可知，Single 和 Multiple 本身并没有任何作用，区分了同一属性的单个配置和多个配置，只是它头上的 @EnableConfigurationBeanBinding 的注解背后的解析器 ConfigurationBeanBindingRegistrar 起了作用。
public class DubboConfigConfiguration {
@EnableConfigurationBeanBindings({
@EnableConfigurationBeanBinding(prefix = "dubbo.application", type = ApplicationConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.module", type = ModuleConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.registry", type = RegistryConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.protocol", type = ProtocolConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.monitor", type = MonitorConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.provider", type = ProviderConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.consumer", type = ConsumerConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.config-center", type = ConfigCenterBean.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.metadata-report", type = MetadataReportConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.metrics", type = MetricsConfig.class),
@EnableConfigurationBeanBinding(prefix = "dubbo.ssl", type = SslConfig.class)
})
public static class Single {
}
@EnableConfigurationBeanBindings({
@EnableConfigurationBeanBinding(prefix = "dubbo.applications", type = ApplicationConfig.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.modules", type = ModuleConfig.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.registries", type = RegistryConfig.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.protocols", type = ProtocolConfig.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.monitors", type = MonitorConfig.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.providers", type = ProviderConfig.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.consumers", type = ConsumerConfig.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.config-centers", type = ConfigCenterBean.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.metadata-reports", type = MetadataReportConfig.class, multiple = true),
@EnableConfigurationBeanBinding(prefix = "dubbo.metricses", type = MetricsConfig.class, multiple = true)
})
public static class Multiple {
}
}
@EnableConfigurationBeanBinding
@EnableConfigurationBeanBinding 注解 prefix 的值代表 .properties 文件配置项 key 的前缀，完整的 key 就会映射到 type 代表类的属性。
@Target({ElementType.TYPE, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import({ConfigurationBeanBindingRegistrar.class})
public @interface EnableConfigurationBeanBinding {
boolean DEFAULT_MULTIPLE = false;
boolean DEFAULT_IGNORE_UNKNOWN_FIELDS = true;
boolean DEFAULT_IGNORE_INVALID_FIELDS = true;
String prefix();
Class<?> type();
boolean multiple() default false;
boolean ignoreUnknownFields() default true;
boolean ignoreInvalidFields() default true;
}
ConfigurationBeanBindingRegistrar
ConfigurationBeanBindingRegistrar 读取 @EnableConfigurationBeanBinding 的 type 属性来注册 bean。
public class ConfigurationBeanBindingRegistrar implements ImportBeanDefinitionRegistrar, EnvironmentAware {
// ......
public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
Map<String, Object> attributes = metadata.getAnnotationAttributes(ENABLE_CONFIGURATION_BINDING_CLASS_NAME);
this.registerConfigurationBeanDefinitions(attributes, registry);
}
// 读取 @EnableConfigurationBeanBinding 里的各种属性
public void registerConfigurationBeanDefinitions(Map<String, Object> attributes, BeanDefinitionRegistry registry) {
String prefix = (String)AnnotationUtils.getRequiredAttribute(attributes, "prefix");
prefix = this.environment.resolvePlaceholders(prefix);
Class<?> configClass = (Class)AnnotationUtils.getRequiredAttribute(attributes, "type");
boolean multiple = (Boolean)AnnotationUtils.getAttribute(attributes, "multiple", false);
boolean ignoreUnknownFields = (Boolean)AnnotationUtils.getAttribute(attributes, "ignoreUnknownFields", true);
boolean ignoreInvalidFields = (Boolean)AnnotationUtils.getAttribute(attributes, "ignoreInvalidFields", true);
this.registerConfigurationBeans(prefix, configClass, multiple, ignoreUnknownFields, ignoreInvalidFields, registry);
}
// 根据 type 属性来批量注册 bean
private void registerConfigurationBeans(String prefix, Class<?> configClass, boolean multiple, boolean ignoreUnknownFields, boolean ignoreInvalidFields, BeanDefinitionRegistry registry) {
Map<String, Object> configurationProperties = PropertySourcesUtils.getSubProperties(this.environment.getPropertySources(), this.environment, prefix);
if (CollectionUtils.isEmpty(configurationProperties)) {
if (this.log.isDebugEnabled()) {
this.log.debug("There is no property for binding to configuration class [" + configClass.getName() + "] within prefix [" + prefix + "]");
}
} else {
Set<String> beanNames = multiple ? this.resolveMultipleBeanNames(configurationProperties) : Collections.singleton(this.resolveSingleBeanName(configurationProperties, configClass, registry));
Iterator var9 = beanNames.iterator();
while(var9.hasNext()) {
String beanName = (String)var9.next();
this.registerConfigurationBean(beanName, configClass, multiple, ignoreUnknownFields, ignoreInvalidFields, configurationProperties, registry);
}
// 注册 bean 实例化前后逻辑
this.registerConfigurationBindingBeanPostProcessor(registry);
}
}
// 实际单个 bean 注册逻辑
private void registerConfigurationBean(String beanName, Class<?> configClass, boolean multiple, boolean ignoreUnknownFields, boolean ignoreInvalidFields, Map<String, Object> configurationProperties, BeanDefinitionRegistry registry) {
BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(configClass);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
this.setSource(beanDefinition);
Map<String, Object> subProperties = this.resolveSubProperties(multiple, beanName, configurationProperties);
ConfigurationBeanBindingPostProcessor.initBeanMetadataAttributes(beanDefinition, subProperties, ignoreUnknownFields, ignoreInvalidFields);
registry.registerBeanDefinition(beanName, beanDefinition);
if (this.log.isInfoEnabled()) {
this.log.info("The configuration bean definition [name : " + beanName + ", content : " + beanDefinition + "] has been registered.");
}
}
// 选用 ConfigurationBeanBindingPostProcessor 完成注册逻辑增强
private void registerConfigurationBindingBeanPostProcessor(BeanDefinitionRegistry registry) {
BeanRegistrar.registerInfrastructureBean(registry, "configurationBeanBindingPostProcessor", ConfigurationBeanBindingPostProcessor.class);
}
// ......
}
ConfigurationBeanBindingPostProcessor
ConfigurationBeanBindingPostProcessor 继承实现于 Spring 提供的一个接口 BeanPostProcessor，BeanPostProcessor 是 Spring IOC 容器给我们提供的一个扩展接口，在 Spring 容器中完成 bean 实例化、配置以及其他初始化方法前后添加一些自己处理逻辑，调用 postProcessBeforeInitialization() 方法来进行数据绑定。
package org.springframework.beans.factory.config;
public interface BeanPostProcessor {
Object postProcessBeforeInitialization(Object var1, String var2) throws BeansException;
Object postProcessAfterInitialization(Object var1, String var2) throws BeansException;
}
public class ConfigurationBeanBindingPostProcessor implements BeanPostProcessor, BeanFactoryAware {
// ......
// 调用 postProcessBeforeInitialization() 方法来进行数据绑定
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
BeanDefinition beanDefinition = this.getNullableBeanDefinition(beanName);
if (this.isConfigurationBean(bean, beanDefinition)) {
this.bindConfigurationBean(bean, beanDefinition);
this.customize(beanName, bean);
}
return bean;
}
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
// ......
// 数据绑定过程
private void bindConfigurationBean(Object configurationBean, BeanDefinition beanDefinition) {
Map<String, Object> configurationProperties = getConfigurationProperties(beanDefinition);
boolean ignoreUnknownFields = getIgnoreUnknownFields(beanDefinition);
boolean ignoreInvalidFields = getIgnoreInvalidFields(beanDefinition);
this.getConfigurationBeanBinder().bind(configurationProperties, ignoreUnknownFields, ignoreInvalidFields, configurationBean);
if (this.log.isInfoEnabled()) {
this.log.info("The configuration bean [" + configurationBean + "] have been binding by the configuration properties [" + configurationProperties + "]");
}
}
private void customize(String beanName, Object configurationBean) {
Iterator var3 = this.getConfigurationBeanCustomizers().iterator();
while(var3.hasNext()) {
ConfigurationBeanCustomizer customizer = (ConfigurationBeanCustomizer)var3.next();
customizer.customize(beanName, configurationBean);
}
}
// ......
public ConfigurationBeanBinder getConfigurationBeanBinder() {
if (this.configurationBeanBinder == null) {
this.initConfigurationBeanBinder();
}
return this.configurationBeanBinder;
}
private void initConfigurationBeanBinder() {
if (this.configurationBeanBinder == null) {
try {
this.configurationBeanBinder = (ConfigurationBeanBinder)this.beanFactory.getBean(ConfigurationBeanBinder.class);
} catch (BeansException var2) {
if (this.log.isInfoEnabled()) {
this.log.info("configurationBeanBinder Bean can't be found in ApplicationContext.");
}
this.configurationBeanBinder = this.defaultConfigurationBeanBinder();
}
}
}
// ......
}
@DubboComponentScan
@DubboComponentScan 是 Dubbo 组件扫描注释，扫描类路径以获取将自动注册为 Spring bean 的注释组件，背后的处理器是 DubboComponentScanRegistrar。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(DubboComponentScanRegistrar.class)
public @interface DubboComponentScan {
String[] value() default {};
String[] basePackages() default {};
Class<?>[] basePackageClasses() default {};
}
DubboComponentScanRegistrar
DubboComponentScanRegistrar 继承实现于 Spring 提供的一个接口 ImportBeanDefinitionRegistrar。registerServiceAnnotationBeanPostProcessor() 方法注册一个 ServiceAnnotationBeanPostProcessor，用来扫描 @Service，registerCommonBeans() 方法用来为使用@Reference 等的 Bean 注册。
package org.springframework.context.annotation;
public interface ImportBeanDefinitionRegistrar {
void registerBeanDefinitions(AnnotationMetadata var1, BeanDefinitionRegistry var2);
}
public class DubboComponentScanRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
Set<String> packagesToScan = getPackagesToScan(importingClassMetadata);
registerServiceAnnotationBeanPostProcessor(packagesToScan, registry);
registerCommonBeans(registry);
}
private void registerServiceAnnotationBeanPostProcessor(Set<String> packagesToScan, BeanDefinitionRegistry registry) {
BeanDefinitionBuilder builder = rootBeanDefinition(ServiceAnnotationBeanPostProcessor.class);
builder.addConstructorArgValue(packagesToScan);
builder.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
BeanDefinitionReaderUtils.registerWithGeneratedName(beanDefinition, registry);
}
// 根据配置的包路径扫描
private Set<String> getPackagesToScan(AnnotationMetadata metadata) {
AnnotationAttributes attributes = AnnotationAttributes.fromMap(
metadata.getAnnotationAttributes(DubboComponentScan.class.getName()));
String[] basePackages = attributes.getStringArray("basePackages");
Class<?>[] basePackageClasses = attributes.getClassArray("basePackageClasses");
String[] value = attributes.getStringArray("value");
// Appends value array attributes
Set<String> packagesToScan = new LinkedHashSet<String>(Arrays.asList(value));
packagesToScan.addAll(Arrays.asList(basePackages));
for (Class<?> basePackageClass : basePackageClasses) {
packagesToScan.add(ClassUtils.getPackageName(basePackageClass));
}
if (packagesToScan.isEmpty()) {
return Collections.singleton(ClassUtils.getPackageName(metadata.getClassName()));
}
return packagesToScan;
}
}
@DubboService
ServiceAnnotationBeanPostProcessor
ServiceAnnotationBeanPostProcessor 类已被弃用，其新的实现查看 ServiceClassPostProcessor。
@Deprecated
public class ServiceAnnotationBeanPostProcessor extends ServiceClassPostProcessor {
// ......
}
ServiceClassPostProcessor 继承实现于 Spring 提供的一个接口BeanDefinitionRegistryPostProcessor。当 ServiceClassPostProcessor 的 postProcessBeanDefinitionRegistry() 方法调用时，会扫描 Spring 的 @Service 注解、Dubbo 的 @Service 注解和 @DubboService 注解的类并注册为 Spring Bean。
package org.springframework.beans.factory.support;
public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {
void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry var1) throws BeansException;
}
public class ServiceClassPostProcessor implements BeanDefinitionRegistryPostProcessor, EnvironmentAware,
ResourceLoaderAware, BeanClassLoaderAware {
// 扫描 Spring 的 @Service 注解、Dubbo 的 @Service 注解和 @DubboService 注解
private final static List<Class<? extends Annotation>> serviceAnnotationTypes = asList(
DubboService.class,
Service.class,
com.alibaba.dubbo.config.annotation.Service.class
);
// ......
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
registerBeans(registry, DubboBootstrapApplicationListener.class);
Set<String> resolvedPackagesToScan = resolvePackagesToScan(packagesToScan);
if (!CollectionUtils.isEmpty(resolvedPackagesToScan)) {
registerServiceBeans(resolvedPackagesToScan, registry);
} else {
if (logger.isWarnEnabled()) {
logger.warn("packagesToScan is empty , ServiceBean registry will be ignored!");
}
}
}
// ......
}
registerServiceBeans() 方法中除了将 @Service 注解的类注册为 Spring Bean，内部还调用 registerServiceBean() 方法注册一个 ServiceBean，这个对象内部有个 ref 属性指向 @Service 类 bean。
/**
* Registers {@link ServiceBean} from new annotated {@link Service} {@link BeanDefinition}
*
* @param beanDefinitionHolder
* @param registry
* @param scanner
* @see ServiceBean
* @see BeanDefinition
*/
private void registerServiceBean(BeanDefinitionHolder beanDefinitionHolder, BeanDefinitionRegistry registry,
DubboClassPathBeanDefinitionScanner scanner) {
Class<?> beanClass = resolveClass(beanDefinitionHolder);
Annotation service = findServiceAnnotation(beanClass);
AnnotationAttributes serviceAnnotationAttributes = getAnnotationAttributes(service, false, false);
Class<?> interfaceClass = resolveServiceInterfaceClass(serviceAnnotationAttributes, beanClass);
String annotatedServiceBeanName = beanDefinitionHolder.getBeanName();
// 注册定义一个 ServiceBean
AbstractBeanDefinition serviceBeanDefinition =
buildServiceBeanDefinition(service, serviceAnnotationAttributes, interfaceClass, annotatedServiceBeanName);
// ServiceBean Bean name
String beanName = generateServiceBeanName(serviceAnnotationAttributes, interfaceClass);
if (scanner.checkCandidate(beanName, serviceBeanDefinition)) { // check duplicated candidate bean
registry.registerBeanDefinition(beanName, serviceBeanDefinition);
if (logger.isInfoEnabled()) {
logger.info("The BeanDefinition[" + serviceBeanDefinition +
"] of ServiceBean has been registered with name : " + beanName);
}
} else {
if (logger.isWarnEnabled()) {
logger.warn("The Duplicated BeanDefinition[" + serviceBeanDefinition +
"] of ServiceBean[ bean name : " + beanName +
"] was be found , Did @DubboComponentScan scan to same package in many times?");
}
}
}
ServiceBean
ServiceBean 继承于 ServiceConfig，并且实现了 InitializingBean 接口，在 afterPropertiesSet() 方法被调用的时候会通过 applicationContext 查找 Dubbo Provider 需要的配置，而这些配置早已通过@EnableDubboConfig 注册到了 Spring 中，完整的 ServiceBean 实例化就完成了。
public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean,
ApplicationContextAware, BeanNameAware, ApplicationEventPublisherAware {
// ......
@Override
public void afterPropertiesSet() throws Exception {
if (StringUtils.isEmpty(getPath())) {
if (StringUtils.isNotEmpty(beanName)
&& StringUtils.isNotEmpty(getInterface())
&& beanName.startsWith(getInterface())) {
setPath(beanName);
}
}
}
}
@DubboReference
ReferenceAnnotationBeanPostProcessor
ReferenceAnnotationBeanPostProcessor 继承实现于 Spring 提供的一个抽象类 AbstractAnnotationBeanPostProcessor。当 ReferenceAnnotationBeanPostProcessor 的 doGetInjectedBean() 方法调用时，会扫描 Spring 的 @Reference 注解、Dubbo 的 @Reference 注解和 @DubboReference 注解并通过 JDK 动态代理创建一个代理对象，这个代理对象的目标对象是 ReferenceBean，这个 ReferenceBean 继承于在 API 配置中提到的 ReferenceConfig。
package com.alibaba.spring.beans.factory.annotation;
public abstract class AbstractAnnotationBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter implements MergedBeanDefinitionPostProcessor, PriorityOrdered, BeanFactoryAware, BeanClassLoaderAware, EnvironmentAware, DisposableBean {
// ......
}
public class ReferenceAnnotationBeanPostProcessor extends AbstractAnnotationBeanPostProcessor implements
ApplicationContextAware, ApplicationListener<ServiceBeanExportedEvent> {
// ......
// 扫描 Spring 的 @Reference 注解、Dubbo 的 @Reference 注解和 @DubboReference 注解
public ReferenceAnnotationBeanPostProcessor() {
super(
DubboReference.class,
Reference.class,
com.alibaba.dubbo.config.annotation.Reference.class);
}
// ......
@Override
protected Object doGetInjectedBean(AnnotationAttributes attributes, Object bean, String beanName, Class<?> injectedType,
InjectionMetadata.InjectedElement injectedElement) throws Exception {
String referencedBeanName = buildReferencedBeanName(attributes, injectedType);
String referenceBeanName = getReferenceBeanName(attributes, injectedType);
// 注册定义一个 ReferenceBean
ReferenceBean referenceBean = buildReferenceBeanIfAbsent(referenceBeanName, attributes, injectedType);
boolean localServiceBean = isLocalServiceBean(referencedBeanName, referenceBean, attributes);
registerReferenceBean(referencedBeanName, referenceBean, attributes, localServiceBean, injectedType);
cacheInjectedReferenceBean(referenceBean, injectedElement);
// 通过 JDK 动态代理创建一个代理对象
return getOrCreateProxy(referencedBeanName, referenceBean, localServiceBean, injectedType);
}
// ......
private ReferenceBean buildReferenceBeanIfAbsent(String referenceBeanName, AnnotationAttributes attributes, Class<?> referencedType) throws Exception {
// 如果多个地方使用 @Reference 引用同一个服务，需要看他们的的缓存 key 是否一样，
// 如果都是一样的，那么就只会创建一个 ReferenceBean
ReferenceBean<?> referenceBean = referenceBeanCache.get(referenceBeanName);
if (referenceBean == null) {
ReferenceBeanBuilder beanBuilder = ReferenceBeanBuilder
.create(attributes, applicationContext)
.interfaceClass(referencedType);
referenceBean = beanBuilder.build();
referenceBeanCache.put(referenceBeanName, referenceBean);
} else if (!referencedType.isAssignableFrom(referenceBean.getInterfaceClass())) {
throw new IllegalArgumentException("reference bean name " + referenceBeanName + " has been duplicated, but interfaceClass " +
referenceBean.getInterfaceClass().getName() + " cannot be assigned to " + referencedType.getName());
}
return referenceBean;
}
private void registerReferenceBean(String referencedBeanName, ReferenceBean referenceBean, AnnotationAttributes attributes, boolean localServiceBean, Class<?> interfaceClass) {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
String beanName = getReferenceBeanName(attributes, interfaceClass);
if (localServiceBean) {
AbstractBeanDefinition beanDefinition = (AbstractBeanDefinition) beanFactory.getBeanDefinition(referencedBeanName);
RuntimeBeanReference runtimeBeanReference = (RuntimeBeanReference) beanDefinition.getPropertyValues().get("ref");
String serviceBeanName = runtimeBeanReference.getBeanName();
beanFactory.registerAlias(serviceBeanName, beanName);
} else {
if (!beanFactory.containsBean(beanName)) {
beanFactory.registerSingleton(beanName, referenceBean);
}
}
}
private void cacheInjectedReferenceBean(ReferenceBean referenceBean, InjectionMetadata.InjectedElement injectedElement) {
if (injectedElement.getMember() instanceof Field) {
injectedFieldReferenceBeanCache.put(injectedElement, referenceBean);
} else if (injectedElement.getMember() instanceof Method) {
injectedMethodReferenceBeanCache.put(injectedElement, referenceBean);
}
}
private Object getOrCreateProxy(String referencedBeanName, ReferenceBean referenceBean, boolean localServiceBean, Class<?> serviceInterfaceType) {
if (localServiceBean) {
return newProxyInstance(getClassLoader(), new Class[]{serviceInterfaceType},
newReferencedBeanInvocationHandler(referencedBeanName));
} else {
exportServiceBeanIfNecessary(referencedBeanName);
return referenceBean.get();
}
}
// ......
}
ReferenceBean
ReferenceBean 是通过 ReferenceBeanBuilder 的 build() 方法，首先通过 doBuild() 方法 new 一个空ReferenceBean 对象，然后调用 configureBean() 方法完成这个空对象的配置。
public class ReferenceBean<T> extends ReferenceConfig<T> implements FactoryBean,
ApplicationContextAware, InitializingBean, DisposableBean {
// ......
@Override
public void afterPropertiesSet() throws Exception {
prepareDubboConfigBeans();
if (init == null) {
init = false;
if (shouldInit()) {
getObject();
}
}
private void prepareDubboConfigBeans() {
beansOfTypeIncludingAncestors(applicationContext, ApplicationConfig.class);
beansOfTypeIncludingAncestors(applicationContext, ModuleConfig.class);
beansOfTypeIncludingAncestors(applicationContext, RegistryConfig.class);
beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class);
beansOfTypeIncludingAncestors(applicationContext, MonitorConfig.class);
beansOfTypeIncludingAncestors(applicationContext, ProviderConfig.class);
beansOfTypeIncludingAncestors(applicationContext, ConsumerConfig.class);
beansOfTypeIncludingAncestors(applicationContext, ConfigCenterBean.class);
beansOfTypeIncludingAncestors(applicationContext, MetadataReportConfig.class);
beansOfTypeIncludingAncestors(applicationContext, MetricsConfig.class);
beansOfTypeIncludingAncestors(applicationContext, SslConfig.class);
}
}
DubboBeanUtils
DubboBeanUtils 在 DubboConfigConfigurationRegistrar，DubboComponentScanRegistrar 中都有被调用到。DubboBeanUtils 使用的 registerInfrastructureBean() 方法其实就是调用 BeanRegistrar.registerInfrastructureBean() 方法来进行数据绑定。
public interface DubboBeanUtils {
/**
* Register the common beans
*
* @param registry {@link BeanDefinitionRegistry}
* @see ReferenceAnnotationBeanPostProcessor
* @see DubboConfigDefaultPropertyValueBeanPostProcessor
* @see DubboConfigAliasPostProcessor
* @see DubboLifecycleComponentApplicationListener
* @see DubboBootstrapApplicationListener
*/
static void registerCommonBeans(BeanDefinitionRegistry registry) {
registerInfrastructureBean(registry, ReferenceAnnotationBeanPostProcessor.BEAN_NAME,
ReferenceAnnotationBeanPostProcessor.class);
registerInfrastructureBean(registry, DubboConfigAliasPostProcessor.BEAN_NAME,
DubboConfigAliasPostProcessor.class);
registerInfrastructureBean(registry, DubboLifecycleComponentApplicationListener.BEAN_NAME,
DubboLifecycleComponentApplicationListener.class);
registerInfrastructureBean(registry, DubboBootstrapApplicationListener.BEAN_NAME,
DubboBootstrapApplicationListener.class);
registerInfrastructureBean(registry, DubboConfigDefaultPropertyValueBeanPostProcessor.BEAN_NAME,
DubboConfigDefaultPropertyValueBeanPostProcessor.class);
}
}
BeanRegistrar
BeanRegistrar.registerInfrastructureBean() 方法是抽象出一个通过 bean 定义、bean 处理器名称和 bean 处理器类型三个参数为注册 bean 数据绑定的一个公共方法。提取了如 ReferenceAnnotationBeanPostProcessor，DubboConfigAliasPostProcessor 等多种处理器的数据绑定公共部分逻辑。
public abstract class BeanRegistrar {
// ......
public static boolean registerInfrastructureBean(BeanDefinitionRegistry beanDefinitionRegistry, String beanName, Class<?> beanType) {
boolean registered = false;
if (!beanDefinitionRegistry.containsBeanDefinition(beanName)) {
RootBeanDefinition beanDefinition = new RootBeanDefinition(beanType);
beanDefinition.setRole(2);
beanDefinitionRegistry.registerBeanDefinition(beanName, beanDefinition);
registered = true;
if (log.isInfoEnabled()) {
log.info("The Infrastructure bean definition [" + beanDefinition + "with name [" + beanName + "] has been registered.");
}
}
return registered;
}
// ......
}