唉... 学艺不精。重学一下Spring 再来接着分析Dubbo源码吧
思路
通过Enable导入关键类
@Configuration
//作用 扫描 @DubboService注解 @DubboRef
@EnableDubbo(scanBasePackages = "cn.enjoy")
@PropertySource("classpath:/dubbo-provider.properties")
public class ProviderConfiguration {
}
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
// 重点在这两个注解
@EnableDubboConfig
@DubboComponentScan
public @interface EnableDubbo {
}
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
// 看他看他看他
@Import(DubboComponentScanRegistrar.class)
public @interface DubboComponentScan {
}
DubboComponentScanRegistrar
为什么能够进入这个方法呢？是在 Spring的 ConfigurationClassPostProcessor 类
// 实现 ImportBeanDefinitionRegistrar 会在Spring refresh 方法中 调用 registerBeanDefinitions方法
// 主要用来实现动态注册BeanDefinition
public class DubboComponentScanRegistrar implements ImportBeanDefinitionRegistrar {
// 注册 Spring BeanDefinition
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
// 注册一些公共的 Bean DubboBeanUtils
// 客户端引用服务的 依赖注入（代理对象）、Spring初始化完成监听（dubbo服务发布）
registerCommonBeans(registry);
Set<String> packagesToScan = getPackagesToScan(importingClassMetadata);
// 扫描@DubboService注解
registerServiceAnnotationPostProcessor(packagesToScan, registry);
}
/**
* Registers {@link ServiceAnnotationPostProcessor}
*
* @param packagesToScan packages to scan without resolving placeholders
* @param registry {@link BeanDefinitionRegistry}
* @since 2.5.8
*/
private void registerServiceAnnotationPostProcessor(Set<String> packagesToScan, BeanDefinitionRegistry registry) {
BeanDefinitionBuilder builder = rootBeanDefinition(ServiceAnnotationPostProcessor.class);
builder.addConstructorArgValue(packagesToScan);
builder.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
BeanDefinitionReaderUtils.registerWithGeneratedName(beanDefinition, registry);
}
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;
}
}
DubboBeanUtils
public interface DubboBeanUtils {
static final Log log = LogFactory.getLog(DubboBeanUtils.class);
/**
* Register the common beans
*
* @param registry {@link BeanDefinitionRegistry}
* @see ReferenceAnnotationBeanPostProcessor
* @see DubboConfigDefaultPropertyValueBeanPostProcessor
* @see DubboConfigAliasPostProcessor
* @see DubboBootstrapApplicationListener
*/
static void registerCommonBeans(BeanDefinitionRegistry registry) {
registerInfrastructureBean(registry, ServicePackagesHolder.BEAN_NAME, ServicePackagesHolder.class);
registerInfrastructureBean(registry, ReferenceBeanManager.BEAN_NAME, ReferenceBeanManager.class);
// Since 2.5.7 Register @Reference Annotation Bean Processor as an infrastructure Bean
// @DubboReference 注解引用的其他服务的类实例，此处会使用代理模式 生成客户端代理对象
registerInfrastructureBean(registry, ReferenceAnnotationBeanPostProcessor.BEAN_NAME,
ReferenceAnnotationBeanPostProcessor.class);
// TODO Whether DubboConfigAliasPostProcessor can be removed ?
// Since 2.7.4 [Feature] https://github.com/apache/dubbo/issues/5093
registerInfrastructureBean(registry, DubboConfigAliasPostProcessor.BEAN_NAME,
DubboConfigAliasPostProcessor.class);
// Since 2.7.4 Register DubboBootstrapApplicationListener as an infrastructure Bean
registerInfrastructureBean(registry, DubboBootstrapApplicationListener.BEAN_NAME,
DubboBootstrapApplicationListener.class);
// Since 2.7.6 Register DubboConfigDefaultPropertyValueBeanPostProcessor as an infrastructure Bean
registerInfrastructureBean(registry, DubboConfigDefaultPropertyValueBeanPostProcessor.BEAN_NAME,
DubboConfigDefaultPropertyValueBeanPostProcessor.class);
// Dubbo config initializer
registerInfrastructureBean(registry, DubboConfigBeanInitializer.BEAN_NAME, DubboConfigBeanInitializer.class);
// register infra bean if not exists later
registerInfrastructureBean(registry, DubboInfraBeanRegisterPostProcessor.BEAN_NAME, DubboInfraBeanRegisterPostProcessor.class);
}
/**
* Register Infrastructure Bean
*
* @param beanDefinitionRegistry {@link BeanDefinitionRegistry}
* @param beanType the type of bean
* @param beanName the name of bean
* @return if it's a first time to register, return <code>true</code>, or <code>false</code>
*/
static boolean registerInfrastructureBean(BeanDefinitionRegistry beanDefinitionRegistry,
String beanName,
Class<?> beanType) {
boolean registered = false;
if (!beanDefinitionRegistry.containsBeanDefinition(beanName)) {
RootBeanDefinition beanDefinition = new RootBeanDefinition(beanType);
beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
beanDefinitionRegistry.registerBeanDefinition(beanName, beanDefinition);
registered = true;
if (log.isDebugEnabled()) {
log.debug("The Infrastructure bean definition [" + beanDefinition
+ "with name [" + beanName + "] has been registered.");
}
}
return registered;
}
}
