SpringCloud @RefreshScope注解源码层面深入分析

@RestController
@RefreshScope
public class ConsumerController {
    @Value("${consumer.value:moren}")
    private String value;
    @RequestMapping("/consumer")
    public String consumer(){
        return value;
    }
}

@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;
}

protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
		for (String basePackage : basePackages) {
			Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
			for (BeanDefinition candidate : candidates) {   
                // 解析当前类上是否存在@scope注解
				ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
				…………
				if (checkCandidate(beanName, candidate)) {
					BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
                    // 生成Scope代理类
					definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
					beanDefinitions.add(definitionHolder);
					registerBeanDefinition(definitionHolder, this.registry);
				}
			}
		}
		return beanDefinitions;
	}
	@Override
	public ScopeMetadata resolveScopeMetadata(BeanDefinition definition) {
		if (definition instanceof AnnotatedBeanDefinition) {
			AnnotatedBeanDefinition annDef = (AnnotatedBeanDefinition) definition;
			AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(
					annDef.getMetadata(), this.scopeAnnotationType);
		}
		return metadata;
	}
protected Class<? extends Annotation> scopeAnnotationType = Scope.class;

public static BeanDefinitionHolder createScopedProxy(BeanDefinitionHolder definition,
			BeanDefinitionRegistry registry, boolean proxyTargetClass) {
        // 拿到原类的名字，和对应的BeanDefinition
		String originalBeanName = definition.getBeanName();
		BeanDefinition targetDefinition = definition.getBeanDefinition();
		String targetBeanName = getTargetBeanName(originalBeanName);
        // 手动创建Scope代理类的BeanDefinition
        // 设置BeanDefinition的BeanClass为ScopedProxyFactoryBean
		RootBeanDefinition proxyDefinition = new RootBeanDefinition(ScopedProxyFactoryBean.class);
		proxyDefinition.setDecoratedDefinition(new BeanDefinitionHolder(targetDefinition, targetBeanName));
		proxyDefinition.setOriginatingBeanDefinition(targetDefinition);
		proxyDefinition.setSource(definition.getSource());
		proxyDefinition.setRole(targetDefinition.getRole());
        …………
        // 将代理类设置为自动注入，并且优先级最高。        
        proxyDefinition.setAutowireCandidate(targetDefinition.isAutowireCandidate());
		proxyDefinition.setPrimary(targetDefinition.isPrimary());
		// 将原类设置为不能自动注入
		targetDefinition.setAutowireCandidate(false);
		targetDefinition.setPrimary(false);
		// 将原类的BeanDefinition注册到工厂中
		registry.registerBeanDefinition(targetBeanName, targetDefinition);
		return new BeanDefinitionHolder(proxyDefinition, originalBeanName, definition.getAliases());
	}
public static String getTargetBeanName(String originalBeanName) {
	return TARGET_NAME_PREFIX + originalBeanName;
}
private static final String TARGET_NAME_PREFIX = "scopedTarget.";

@Bean
@ConditionalOnMissingBean(RefreshScope.class)
public static RefreshScope refreshScope() {
	return new RefreshScope();
}
@Bean
@ConditionalOnMissingBean
@ConditionalOnBootstrapEnabled
public LegacyContextRefresher legacyContextRefresher(ConfigurableApplicationContext context, RefreshScope scope,
			RefreshProperties properties) {
	return new LegacyContextRefresher(context, scope, properties);
}
@Bean
public RefreshEventListener refreshEventListener(ContextRefresher contextRefresher) {
	return new RefreshEventListener(contextRefresher);
}

public class RefreshScope extends GenericScope
		implements ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, Ordered 
// RefreshScope的父类
// 实现了BeanFactoryPostProcessor扩展接口
public class GenericScope
		implements Scope, BeanFactoryPostProcessor, BeanDefinitionRegistryPostProcessor, DisposableBean 
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
	this.beanFactory = beanFactory;
    // 把当前Scope注册到BeanFacotry中。
	beanFactory.registerScope(this.name, this);
	setSerializationId(beanFactory);
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
	for (String name : registry.getBeanDefinitionNames()) {
		BeanDefinition definition = registry.getBeanDefinition(name);
		if (definition instanceof RootBeanDefinition) {
			RootBeanDefinition root = (RootBeanDefinition) definition;
			if (root.getDecoratedDefinition() != null && root.hasBeanClass()
					&& root.getBeanClass() == ScopedProxyFactoryBean.class) {
				if(getName().equals(root.getDecoratedDefinition().getBeanDefinition().getScope())) {
                    // 再一次的偷天换日
					root.setBeanClass(LockedScopedProxyFactoryBean.class);
					root.getConstructorArgumentValues().addGenericArgumentValue(this);
					root.setSynthetic(true);
				}
			}
		}
	}
}

// SmartApplicationListener子类监听器
public class RefreshEventListener implements SmartApplicationListener 
// 事件回掉。
@Override
public void onApplicationEvent(ApplicationEvent event) {
	if (event instanceof ApplicationReadyEvent) {
		handle((ApplicationReadyEvent) event);
	}
    // 一定要注意到RefreshEvent事件，非常非常非常重要！！！
    // 后续我们只需要找到哪里发出的这个事件即可。
	else if (event instanceof RefreshEvent) {
		handle((RefreshEvent) event);
	}
}
public void handle(RefreshEvent event) {
	if (this.ready.get()) { 
		Set<String> keys = this.refresh.refresh();
	}
}
public synchronized Set<String> refresh() {
    // 刷新Environment上下文。而我们知道配置数据是放在Environment中的。
	Set<String> keys = refreshEnvironment();
    // 调用scope的refreshAll，从方法就可以知道，要刷新所有的数据
	this.scope.refreshAll();
	return keys;
}

public synchronized Set<String> refreshEnvironment() {
    // 拿到更新前的Environment
	Map<String, Object> before = extract(this.context.getEnvironment().getPropertySources());
    // 更新Environment。
	updateEnvironment();
    // 对比更新后和更新前，返回发生变化的数据。
	Set<String> keys = changes(before, extract(this.context.getEnvironment().getPropertySources())).keySet();
	this.context.publishEvent(new EnvironmentChangeEvent(this.context, keys));
	return keys;
}
@Override
protected void updateEnvironment() {
	addConfigFilesToEnvironment();
}
ConfigurableApplicationContext addConfigFilesToEnvironment() {
	ConfigurableApplicationContext capture = null;
	try {
		StandardEnvironment environment = copyEnvironment(getContext().getEnvironment());
		…………
		// 创建一个Spring Boot的启动器，目的：为了创建出Spring的上下文（这样整个上下文刷新就可以得到最新的environment）。
		// 这里要注意，刷新Spring上下文的environment是手动放入的，
		// 也即重新刷新Spring上下文的环境变量会加载到手动创建的environment中
		SpringApplicationBuilder builder = new SpringApplicationBuilder(Empty.class).bannerMode(Banner.Mode.OFF)
		.web(WebApplicationType.NONE).environment(environment);
		builder.application().setListeners(
			Arrays.asList(new BootstrapApplicationListener(), new BootstrapConfigFileApplicationListener()));
		capture = builder.run();
		MutablePropertySources target = getContext().getEnvironment().getPropertySources();
		String targetName = null;
		// 把再次刷新Spring上下文environment得到的数据赋值到原有的environment环境变量中（这不就完成了配置数据的刷新么）
		for (PropertySource<?> source : environment.getPropertySources()) {
			if (!this.standardSources.contains(name)) {
				if (target.contains(name)) {
					target.replace(name, source);
				}
				else {
					if (targetName != null) {
						target.addAfter(targetName, source);
							// update targetName to preserve ordering
						targetName = name;
					}
					else {
							// targetName was null so we are at the start of the list
						target.addFirst(source);
						targetName = name;
					}
				}
			}
		}
	}
	// finally中把临时创建出的Application上下文给关闭。
	finally {
		ConfigurableApplicationContext closeable = capture;
		while (closeable != null) {
			closeable.close();
			if (closeable.getParent() instanceof ConfigurableApplicationContext) {
				closeable = (ConfigurableApplicationContext) closeable.getParent();
			}
			else {
				break;
			}
		}
	}
	return capture;
}

public void refreshAll() {
	super.destroy();
	this.context.publishEvent(new RefreshScopeRefreshedEvent());
}
@Override
public void destroy() {
	List<Throwable> errors = new ArrayList<Throwable>();
    // 清空缓存
	Collection<BeanLifecycleWrapper> wrappers = this.cache.clear();
    // 调用摧毁的回掉函数
	for (BeanLifecycleWrapper wrapper : wrappers) {
		try {
			Lock lock = this.locks.get(wrapper.getName()).writeLock();
			lock.lock();
			try {
				wrapper.destroy();
			}
			finally {
				lock.unlock();
			}
		}
		catch (RuntimeException e) {
			errors.add(e);
		}
	}
}

protected <T> T doGetBean(String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
    // 创建singleton的bean
	if (mbd.isSingleton()) {
        …………
	}
    // 创建Prototype的bean
	else if (mbd.isPrototype()) {
		…………
	}
    // 创建其他Scope作用域的bean
	else {
		String scopeName = mbd.getScope();
		if (!StringUtils.hasLength(scopeName)) {
			throw new IllegalStateException("No scope name defined for bean '" + beanName + "'");
		}
        // 根据name拿到对应的Scope。
		Scope scope = this.scopes.get(scopeName);
		if (scope == null) {
			throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
		}
		try {
            // 调用scope的get方法，所以对应的scope可以缓存。
			Object scopedInstance = scope.get(beanName, () -> {
				beforePrototypeCreation(beanName);
				try {
					return createBean(beanName, mbd, args);
				}
				finally {
					afterPrototypeCreation(beanName);
				}
			});
			beanInstance = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
		}
		catch (IllegalStateException ex) {
			throw new ScopeNotActiveException(beanName, scopeName, ex);
		}
	}
}

public static class LockedScopedProxyFactoryBean<S extends GenericScope> extends ScopedProxyFactoryBean
			implements MethodInterceptor {
    @Override
    public Object invoke(MethodInvocation invocation) throws Throwable {
	    // 反射的Method
        Method method = invocation.getMethod();
	    …………
	    try {
		    if (proxy instanceof Advised) {
			    Advised advised = (Advised) proxy;
			    ReflectionUtils.makeAccessible(method);
			    // advised.getTargetSource().getTarget()方法会去getBean
			    return ReflectionUtils.invokeMethod(method, advised.getTargetSource().getTarget(),
				invocation.getArguments());
		    }
		    return invocation.proceed();
	    }
    }
}
public class SimpleBeanTargetSource extends AbstractBeanFactoryBasedTargetSource {
	@Override
	public Object getTarget() throws Exception {
		// 看到熟悉的getBean方法了。
		return getBeanFactory().getBean(getTargetBeanName());
	}
}

@Override
public Object get(String name, ObjectFactory<?> objectFactory) {
    // 拿缓存，如果缓存中没有就创建
	BeanLifecycleWrapper value = this.cache.put(name, new BeanLifecycleWrapper(name, objectFactory));
	this.locks.putIfAbsent(name, new ReentrantReadWriteLock());
	try {
        // 拿缓存，如果缓存中没有就回掉createBean方法。
		return value.getBean();
	}
	catch (RuntimeException e) {
		this.errors.put(name, e);
		throw e;
	}
}

public class NacosContextRefresher
implements ApplicationListener<ApplicationReadyEvent>, ApplicationContextAware {
	private void registerNacosListener(final String groupKey, final String dataKey) {
		// 一个group、dataid对应一组事件。
		String key = NacosPropertySourceRepository.getMapKey(dataKey, groupKey);
		// 创建一个Nacos事件监听器
		Listener listener = listenerMap.computeIfAbsent(key,
			lst -> new AbstractSharedListener() {
				@Override
				public void innerReceive(String dataId, String group,
					String configInfo) {
					// 这里发送了RefreshEvent事件。
					applicationContext.publishEvent(
						new RefreshEvent(this, null, "Refresh Nacos config"));
				}
			});
		try {
			// 添加Nacos的内部事件
			configService.addListener(dataKey, groupKey, listener);
		}
	}
}