SpringCloud之RefreshScope
@Scope 源码解读
- Scope(
org.springframework.beans.factory.config.Scope)是Spring 2.0开始就有的核心的概念 - RefreshScope(
org.springframework.cloud.context.scope.refresh)是spring cloud提供的一种特殊的scope实现，用来实现配置、实例热加载。 Scope -> GenericScope -> RefreshScope
- Scope与ApplicationContext生命周期
- AbstractBeanFactory#doGetBean创建Bean实例
protected T doGetBean(...){
final RootBeanDefinition mbd = ...
if (mbd.isSingleton()) {
...
} else if (mbd.isPrototype())
...
} else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
Object scopedInstance = scope.get(beanName, new ObjectFactory - Singleton和Prototype是硬编码的，并不是Scope子类。 Scope实际上是自定义扩展的接口
- Scope Bean实例交由Scope自己创建，例如SessionScope是从Session中获取实例的，ThreadScope是从ThreadLocal中获取的，而RefreshScope是在内建缓存中获取的
- @Scope 对象的实例化
- @RefreshScope 是scopeName="refresh"的 @Scope
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Scope("refresh")
@Documented
public @interface RefreshScope {
/**
* @see Scope#proxyMode()
* @return proxy mode
*/
ScopedProxyMode proxyMode() default ScopedProxyMode.TARGET_CLASS;
}- @Scope 的注册 AnnotatedBeanDefinitionReader#registerBean
public void registerBean(...){
...
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
abd.setScope(scopeMetadata.getScopeName());
...
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
}- 读取@Scope元数据， AnnotationScopeMetadataResolver#resolveScopeMetadata
public ScopeMetadata resolveScopeMetadata(BeanDefinition definition) {
AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(
annDef.getMetadata(), Scope.class);
if (attributes != null) {
metadata.setScopeName(attributes.getString("value"));
ScopedProxyMode proxyMode = attributes.getEnum("proxyMode");
if (proxyMode == null || proxyMode == ScopedProxyMode.DEFAULT) {
proxyMode = this.defaultProxyMode;
}
metadata.setScopedProxyMode(proxyMode);
}
}Scope实例对象通过ScopedProxyFactoryBean创建，其中通过AOP使其实现ScopedObject接口，这里不再展开
@RefreshScope 源码解读
RefreshScope注册
RefreshAutoConfiguration#RefreshScopeConfiguration
@Component
@ConditionalOnMissingBean(RefreshScope.class)
protected static class RefreshScopeConfiguration implements BeanDefinitionRegistryPostProcessor{
...
registry.registerBeanDefinition("refreshScope",
BeanDefinitionBuilder.genericBeanDefinition(RefreshScope.class)
.setRole(BeanDefinition.ROLE_INFRASTRUCTURE)
.getBeanDefinition());
...
}- RefreshScope extends GenericScope, 大部分逻辑在 GenericScope 中
- GenericScope#postProcessBeanFactory 中向AbstractBeanFactory注册自己
public class GenericScope implements Scope, BeanFactoryPostProcessor...{
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
throws BeansException {
beanFactory.registerScope(this.name/*refresh*/, this/*RefreshScope*/);
...
}
}RefreshScope 刷新过程
- 入口在ContextRefresher#refresh
public synchronized Set refresh() {
Set keys = refreshEnvironment();
this.scope.refreshAll();
return keys;
}
public synchronized Set refreshEnvironment() {
Map before = extract(
this.context.getEnvironment().getPropertySources());
addConfigFilesToEnvironment();
Set keys = changes(before,
extract(this.context.getEnvironment().getPropertySources())).keySet();
this.context.publishEvent(new EnvironmentChangeEvent(this.context, keys));
return keys;
} - ①提取标准参数(SYSTEM,JNDI,SERVLET)之外所有参数变量
- ②把原来的Environment里的参数放到一个新建的Spring Context容器下重新加载，完事之后关闭新容器
- ③提起更新过的参数(排除标准参数)
- ④比较出变更项
- ⑤发布环境变更事件,接收：EnvironmentChangeListener／LoggingRebinder
- ⑥RefreshScope用新的环境参数重新生成Bean
- ⑦重新生成的过程很简单，清除refreshscope缓存幷销毁Bean，下次就会重新从BeanFactory获取一个新的实例（该实例使用新的配置）
- ⑧RefreshScope#refreshAll
public void refreshAll() {
super.destroy();
this.context.publishEvent(new RefreshScopeRefreshedEvent());
}- ⑨GenericScope#destroy
public void destroy() {
...
Collection wrappers = this.cache.clear();
for (BeanLifecycleWrapper wrapper : wrappers) {
wrapper.destroy();
}
}