Dubbo服务注册原理
文章目录
- 1注册步骤
- 2 猜想：
- 3源码分析
-
- 3.1 @DubboComponentScan
-
- 3.1.1 图片总结
- 3.2 DubboBootstrapApplicationListener.java
1注册步骤
- 使用注解@DubboService或@Service
- 扫描注解@DubboComponentScan
2 猜想：
（1）扫描注解
（2）组装url
（3）启动服务（根据url中配置的协议、端口去发布对应的服务）
（4）注册到注册中心
3源码分析
3.1 @DubboComponentScan
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import({DubboComponentScanRegistrar.class})
public @interface DubboComponentScan {
String[] value() default {};
String[] basePackages() default {};
Class<?>[] basePackageClasses() default {};
}
DubboComponentScanRegistrar:动态注册bean到IOC中，但是是注册哪个bean?需要分析下源码
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
//获取@DubboComponentScan注解中配置的包路径
Set<String> packagesToScan = getPackagesToScan(importingClassMetadata);
//注册bean到IOC容器中
registerServiceAnnotationBeanPostProcessor(packagesToScan, registry);
// @since 2.7.6 Register the common beans
registerCommonBeans(registry);
}
点击 registerServiceAnnotationBeanPostProcessor(packagesToScan, registry)，可以看到将ServiceAnnotationBeanPostProcessor加载到IOC容器中
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);
}
来看下 ServiceAnnotationBeanPostProcessor.java
public ServiceAnnotationBeanPostProcessor(Set<String> packagesToScan) {
super(packagesToScan);
}
点击父类ServiceClassPostProcessor.java的构造器,在bean加载到IOC之后会触发postProcessBeanDefinitionRegistry方法
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
// @since 2.7.5
//注册基础bean
registerInfrastructureBean(registry, DubboBootstrapApplicationListener.BEAN_NAME, DubboBootstrapApplicationListener.class);
Set<String> resolvedPackagesToScan = resolvePackagesToScan(packagesToScan);
//如果扫描的包路径不为空，注册服务bean：serviceBean
if (!CollectionUtils.isEmpty(resolvedPackagesToScan)) {
registerServiceBeans(resolvedPackagesToScan, registry);
} else {
if (logger.isWarnEnabled()) {
logger.warn("packagesToScan is empty , ServiceBean registry will be ignored!");
}
}
}
registerInfrastructureBean()方法中将DubboBootstrapApplicationListener注册到容器中，
DubboBootstrapApplicationListener中的onApplicationContextEvent()方法会在spring 容器的上下文装载完成之后，触发监听
@Override
public void onApplicationContextEvent(ApplicationContextEvent event) {
if (event instanceof ContextRefreshedEvent) {
onContextRefreshedEvent((ContextRefreshedEvent) event);
} else if (event instanceof ContextClosedEvent) {
onContextClosedEvent((ContextClosedEvent) event);
}
}
再来看下registerServiceBeans(resolvedPackagesToScan, registry) 代码
扫描所有加了@DubboService或@Service注解的bean,但不是注册到IOC容器里
private void registerServiceBeans(Set<String> packagesToScan, BeanDefinitionRegistry registry) {
DubboClassPathBeanDefinitionScanner scanner =
new DubboClassPathBeanDefinitionScanner(registry, environment, resourceLoader);
BeanNameGenerator beanNameGenerator = resolveBeanNameGenerator(registry);
scanner.setBeanNameGenerator(beanNameGenerator);
// refactor @since 2.7.7
serviceAnnotationTypes.forEach(annotationType -> {
scanner.addIncludeFilter(new AnnotationTypeFilter(annotationType));
});
for (String packageToScan : packagesToScan) {
// Registers @Service Bean first
scanner.scan(packageToScan);
// Finds all BeanDefinitionHolders of @Service whether @ComponentScan scans or not.
Set<BeanDefinitionHolder> beanDefinitionHolders =
findServiceBeanDefinitionHolders(scanner, packageToScan, registry, beanNameGenerator);
if (!CollectionUtils.isEmpty(beanDefinitionHolders)) {
for (BeanDefinitionHolder beanDefinitionHolder : beanDefinitionHolders) {
registerServiceBean(beanDefinitionHolder, registry, scanner);
}
if (logger.isInfoEnabled()) {
logger.info(beanDefinitionHolders.size() + " annotated Dubbo's @Service Components { " +
beanDefinitionHolders +
" } were scanned under package[" + packageToScan + "]");
}
} else {
if (logger.isWarnEnabled()) {
logger.warn("No Spring Bean annotating Dubbo's @Service was found under package["
+ packageToScan + "]");
}
}
}
}
点击 registerServiceBean(beanDefinitionHolder, registry, scanner);
private void registerServiceBean(BeanDefinitionHolder beanDefinitionHolder, BeanDefinitionRegistry registry,
DubboClassPathBeanDefinitionScanner scanner) {
Class<?> beanClass = resolveClass(beanDefinitionHolder);
Annotation service = findServiceAnnotation(beanClass);
/**
* The {@link AnnotationAttributes} of @Service annotation
*/
AnnotationAttributes serviceAnnotationAttributes = getAnnotationAttributes(service, false, false);
Class<?> interfaceClass = resolveServiceInterfaceClass(serviceAnnotationAttributes, beanClass);
String annotatedServiceBeanName = beanDefinitionHolder.getBeanName();
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?");
}
}
}
buildServiceBeanDefinition
private AbstractBeanDefinition buildServiceBeanDefinition(Annotation serviceAnnotation,
AnnotationAttributes serviceAnnotationAttributes,
Class<?> interfaceClass,
String annotatedServiceBeanName) {
BeanDefinitionBuilder builder = rootBeanDefinition(ServiceBean.class);
//省略代码
最终将org.apache.dubbo.config.spring.ServiceBean注册到IOC容器中
3.1.1 图片总结
3.2 DubboBootstrapApplicationListener.java
DubboBootstrapApplicationListener.java实现了监听接口，最终会调用ServiceConfig#export()方法，调用过程如下图：
