简单介绍
Spring IOC的核心方法就在于refresh方法，这个方法里面完成了Spring的初始化、准备bean、实例化bean和扩展功能的实现。
- 这个方法的作用是什么？
- 它是如何完成这些功能的？
- 为什么要这样去实现？
- 有哪些值得借鉴的地方？
refresh方法
在ConfigurableApplicationContext里面定义了这个方法：
/**
* Load or refresh the persistent representation of the configuration, which
* might be from Java-based configuration, an XML file, a properties file, a
* relational database schema, or some other format.
* <p>As this is a startup method, it should destroy already created singletons
* if it fails, to avoid dangling resources. In other words, after invocation
* of this method, either all or no singletons at all should be instantiated.
* @throws BeansException if the bean factory could not be initialized
* @throws IllegalStateException if already initialized and multiple refresh
* attempts are not supported
*/
void refresh() throws BeansException, IllegalStateException;
根据注释可以知道，这个方法是用来加载刷新配置，这些配置可能来自java配置、xml文件、properties文件、关系型数据库或者其他格式。
作为一个启动方法，它应当在初始化失败后销毁已经创建的单例，防止占着资源而不使用。也就是说调用这个方法的话，要么所有的单例已经被实例化，要么所有的单例都不存在。
BeansException：bean工厂不能被初始化，抛出BeansException
IllegalStateException：bean工厂已经被初始化了，但是不支持多次刷新，抛出IllegalStateException
具体实现
在AbstractApplicationContext中进行了实现：
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//为刷新做准备，初始化各种状态，启动时间、关闭激活状态、配置文件信息等
prepareRefresh();
//通知子类刷新内部BeanFactory，并返回刷新后的BeanFactory
//关注方法中的refreshBeanFactory方法，两个子类对它重写的差异
//AbstractRefreshableApplicationContext#refreshBeanFactory中重新构建，完成BeanDefinition的解析构建
//GenericApplicationContext#refreshBeanFactory则是设置ID，并且只能刷新一次
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
//给容器准备BeanFactory，配置相关的属性
prepareBeanFactory(beanFactory);
try {
//允许子类处理后置beanFactory
postProcessBeanFactory(beanFactory);
//调用注册了beanFactory后置处理器接口实例bean对应的方法
invokeBeanFactoryPostProcessors(beanFactory);
//注册bean后置处理器接口的实例bean
registerBeanPostProcessors(beanFactory);
//初始化国际化资源
initMessageSource();
//初始化事件传播者
initApplicationEventMulticaster();
//refresh事件，初始化一些指定的bean
onRefresh();
//注册监听器bean
registerListeners();
//完成bean工厂的初始化，初始化所有非懒加载的单例bean
finishBeanFactoryInitialization(beanFactory);
//最后，发布finishRefresh事件
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
//销毁了所有已经创建了的单例bean
destroyBeans();
//重置active标记
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
使用示例：
GenericApplicationContext context3 = new GenericApplicationContext();
new XmlBeanDefinitionReader(context3).loadBeanDefinitions("classpath:application.xml");
new ClassPathBeanDefinitionScanner(context3).scan("edu.demo");
// 一定要刷新
context3.refresh();
IOC容器刷新整体流程
prepareRefresh方法
//关闭和刷新的状态都是AtomicBoolean类型的，原子性
/** Flag that indicates whether this context is currently active. */
private final AtomicBoolean active = new AtomicBoolean();
/** Flag that indicates whether this context has been closed already. */
private final AtomicBoolean closed = new AtomicBoolean();
/**
* 为容器刷新做准备，设置启动日期和活动标识
* 并执行一些资源的初始化
*/
protected void prepareRefresh() {
//容器切换到启动状态
//设置启动容器的时间
this.startupDate = System.currentTimeMillis();
//设置关闭的状态
this.closed.set(false);
//设置启动的状态
this.active.set(true);
if (logger.isDebugEnabled()) {
if (logger.isTraceEnabled()) {
logger.trace("Refreshing " + this);
}
else {
logger.debug("Refreshing " + getDisplayName());
}
}
//初始化容器的占位符资源
initPropertySources();
// 验证所有标记为required的属性都是可解析的:
// see ConfigurablePropertyResolver#setRequiredProperties
getEnvironment().validateRequiredProperties();
//一些监听器的初始化
// Store pre-refresh ApplicationListeners...
if (this.earlyApplicationListeners == null) {
this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
}
else {
// Reset local application listeners to pre-refresh state.
this.applicationListeners.clear();
this.applicationListeners.addAll(this.earlyApplicationListeners);
}
// Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
this.earlyApplicationEvents = new LinkedHashSet<>();
}
obtainFreshBeanFactory方法
/**
* 告诉子类刷新内部的bean factory.
* @return the fresh BeanFactory instance
* @see #refreshBeanFactory()
* @see #getBeanFactory()
*/
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
return getBeanFactory();
}
其实就是配置用户的属性、加载bean定义，并且返回刷新后的bean工厂。prepareBeanFacotry方法内部又有两个抽象方法构成，交给子类去实现。也就是说子类必定含有一个BeanFactory实例，并且还需要提供刷新方法，返回BeanFactory实例的方法。
具体实现类：
- AbstractRefreshableApplicationContext
AbstractRefreshableApplicationContext中实现的刷新方法，可以被多次的调用执行，也就是可以多次刷新。
/**
* 实际的刷新方法。关闭以前的bean工厂，初始化一个新的bean工厂
*/
@Override
protected final void refreshBeanFactory() throws BeansException {
//如果存在bean工厂，则销毁单例bean，关闭bean工厂
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
//创建DefaultListableBeanFactory实例
DefaultListableBeanFactory beanFactory = createBeanFactory();
//设置ID
beanFactory.setSerializationId(getId());
//自定义bean工厂属性，bean定义重新、循环引用等配置
customizeBeanFactory(beanFactory);
//等待子类实现的，向bean工厂注册bean定义
loadBeanDefinitions(beanFactory);
//持有bean工厂的实例，以便在getBeanFactory方法中返回出去
this.beanFactory = beanFactory;
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
//自定义bean工厂属性
protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {
if (this.allowBeanDefinitionOverriding != null) {
beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
if (this.allowCircularReferences != null) {
beanFactory.setAllowCircularReferences(this.allowCircularReferences);
}
}
//关闭bean工厂的方法
@Override
protected final void closeBeanFactory() {
DefaultListableBeanFactory beanFactory = this.beanFactory;
//如果bean工厂存在
if (beanFactory != null) {
//设置ID为空
beanFactory.setSerializationId(null);
//设置bean工厂的实例为空
this.beanFactory = null;
}
}
AbstractApplicationContext类中的销毁方法：
//销毁方法
protected void destroyBeans() {
getBeanFactory().destroySingletons();
}
- GenericApplicationContext
GenericApplicationContext中的刷新方法，只能被调用一次，被AtomicBoolean类型的refreshed控制着
private final AtomicBoolean refreshed = new AtomicBoolean();
/**
* 持有一个内部的bean工厂，通过公共的方法注册bean
* @see #registerBeanDefinition
*/
@Override
protected final void refreshBeanFactory() throws IllegalStateException {
//CAS的方式进行修改
//多次刷新就抛出异常
if (!this.refreshed.compareAndSet(false, true)) {
throw new IllegalStateException(
"GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
}
//设置ID
this.beanFactory.setSerializationId(getId());
}
beanFactory在构造函数中被创建的，代码如下：
/**
* Create a new GenericApplicationContext.
* @see #registerBeanDefinition
* @see #refresh
*/
public GenericApplicationContext() {
this.beanFactory = new DefaultListableBeanFactory();
}
/**
* Create a new GenericApplicationContext with the given DefaultListableBeanFactory.
* @param beanFactory the DefaultListableBeanFactory instance to use for this context
* @see #registerBeanDefinition
* @see #refresh
*/
public GenericApplicationContext(DefaultListableBeanFactory beanFactory) {
Assert.notNull(beanFactory, "BeanFactory must not be null");
this.beanFactory = beanFactory;
}
这个时候的beanFactory里面都有些什么呢？根据之前的注解的加载过程。可以知道，应该有BeanFactoryPostProcessor、BeanPostProcessor、ApplicationListener信息。
prepareBeanFactory方法
/**
* 配置工厂的标准容器特征
* 例如容器的ClassLoader和post-processor
* @param beanFactory the BeanFactory to configure
*/
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
//给bean工作准备ClassLoader、SPL表达式解析器、属性编辑注册器等
beanFactory.setBeanClassLoader(getClassLoader());
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
//向beanFactory注册ApplicationContextAwareProcessor
//后面的六种Aware忽略他们的自动依赖注入
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// BeanFactory interface not registered as resolvable type in a plain factory.
// MessageSource registered (and found for autowiring) as a bean.
//依赖需要使用的bean，IOC容器自己的多角色身份，@Autowried方式获得下列类型bean
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// Register early post-processor for detecting inner beans as ApplicationListeners.
//注入ApplicationListeners接口实现的发现处理器，同时带有销毁、bean定义混合的实现
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// Register default environment beans.
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
// properties配置文件
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
// 操作系统环境变量：JAVA_HOME等
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
ApplicationContextAwareProcessor方法中的，注入Processor
@Override
@Nullable
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
//只针对EnvironmentAware、EmbeddedValueResolverAware、ResourceLoaderAware、ApplicationEventPublisherAware、MessageSourceAware、ApplicationContextAware 6种实现进行处理。
if (!(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)){
return bean;
}
AccessControlContext acc = null;
if (System.getSecurityManager() != null) {
acc = this.applicationContext.getBeanFactory().getAccessControlContext();
}
if (acc != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareInterfaces(bean);
return null;
}, acc);
}
else {
invokeAwareInterfaces(bean);
}
return bean;
}
//将beanFactory注入给上述的6种Aware
private void invokeAwareInterfaces(Object bean) {
if (bean instanceof EnvironmentAware) {
((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
}
if (bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
}
if (bean instanceof ResourceLoaderAware) {
((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
}
if (bean instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
}
if (bean instanceof MessageSourceAware) {
((MessageSourceAware) bean).setMessageSource(this.applicationContext);
}
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
}
postProcessBeanFactory方法
postProcessBeanFactory方法并没有去实现它。
/**
* Modify the application context's internal bean factory after its standard
* initialization. All bean definitions will have been loaded, but no beans
* will have been instantiated yet. This allows for registering special
* BeanPostProcessors etc in certain ApplicationContext implementations.
* @param beanFactory the bean factory used by the application context
*/
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
}
invokeBeanFactoryPostProcessors方法
这个时候，bean工厂基本上已经准备完成，但是bean实例还没有进行初始化，接下来调用BeanFactoryPostProcessor对Bean工厂中的Bean定义进行调整
/**
* 执行BeanFactoryPostProcessor
* <p>必须在单例bean实例化之前调用
*/
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
//最重要的处理在委托里面实现
//getBeanFactoryPostProcessors()获取的是容器里面的列表属性，
//这个属性没有机会给外部去注入BeanFactoryPostProcessor对象。
//因为ApplicationContext子类在构造函数中调用了refresh方法。所以这里是个空值
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
invokeBeanFactoryPostProcessors方法：
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
//BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
//获取BeanDefinitionRegistryPostProcessor
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
//这里既然做了处理，为何又加入到了registryProcessors集合中？
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest.
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
//第一步，处理继承PriorityOrdered的BeanDefinitionRegistryPostProcessors
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
//第二步，处理继承自Ordered的BeanDefinitionRegistryPostProcessors
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
//最后一步，处理没有优先顺序的BeanDefinitionRegistryPostProcessors
boolean reiterate = true;
while (reiterate) {
reiterate = false;
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
//回调
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
//处理BeanFactoryPostProcessor，按照PriorityOrdered、Ordered和其他
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
//第一步，处理继承自PriorityOrdered的BeanFactoryPostProcessors
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
//第二步，处理继承自Ordered的BeanFactoryPostProcessors
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
//最后一步，处理其他的BeanFactoryPostProcessors
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
//清除缓存，因为后面的处理器可能会修改元数据
beanFactory.clearMetadataCache();
}
从上面的源码部分可以看到：
- 拆成了两部分：registryProcessors、regularPostProcessors，分别处理BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor
- 排序处理：PriorityOrdered、Ordered和为排序的，按照这样的优先级进行处理
多次调用了invokeBeanFactoryPostProcessors，因为在调用BeanFactoryPostProcessors的过程中，还会继续产生BeanFactoryPostProcessors，这里多次调用，就是为了处理掉所有的BeanFactoryPostProcessors。
registerBeanPostProcessors方法
到了这一步，bean定义已经加载完成，bean工厂完成了刷新和实例化，而且通过BeanFactoryProcessor修整了bean定义信息，接下来注册BeanPostProcessors
/**
* Instantiate and register all BeanPostProcessor beans,
* respecting explicit order if given.
* <p>Must be called before any instantiation of application beans.
*/
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
PostProcessorRegistrationDelegate的registerBeanPostProcessors方法：
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
可以看到上面的源码部分，和与BeanFactroyPostProcessor的处理简直一样，排序然后调用处理逻辑。
- priorityOrderedPostProcessors
- orderedPostProcessors
- nonOrderedPostProcessors
- internalPostProcessors
- ApplicationListenerDetector
下面是排序的实例：
- 没有继承任何排序的接口：
@Component
public class MyBeanDefinitonRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("--- MyBeanDefinitonRegistryPostProcessor.postProcessBeanFactory 被执行了。");
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("--- MyBeanDefinitonRegistryPostProcessor.postProcessBeanDefinitionRegistry 被执行了。");
}
}
- 继承Ordered接口：
@Component
public class MyBeanDefinitonRegistryPostProcessor2 implements BeanDefinitionRegistryPostProcessor, Ordered {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("--- MyBeanDefinitonRegistryPostProcessor2.postProcessBeanFactory 被执行了。");
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("--- MyBeanDefinitonRegistryPostProcessor2.postProcessBeanDefinitionRegistry 被执行了。");
}
@Override
public int getOrder() {
return 0;
}
}
- 继承PriorityOrdered接口：
@Component
public class MyBeanDefinitonRegistryPostProcessor3 implements BeanDefinitionRegistryPostProcessor, PriorityOrdered {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("--- MyBeanDefinitonRegistryPostProcessor3.postProcessBeanFactory 被执行了。");
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("--- MyBeanDefinitonRegistryPostProcessor3.postProcessBeanDefinitionRegistry 被执行了。");
}
@Override
public int getOrder() {
return 1;
}
}
执行结果如下：
从上图可以清楚的看到，PriorityOrdered > Ordered > 未排序
initMessageSource方法
此时BenPostProcessor都已经注册完成，下一步就是准备国际化资源：
/**
* 初始化国际化资源，如果没有，就使用父类的
*/
protected void initMessageSource() {
//获取bean工厂
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
//如果Bean工厂中存在名为messageSource的bean，则使用它
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
// Make MessageSource aware of parent MessageSource.
//获取父类的MessageSource
if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
if (hms.getParentMessageSource() == null) {
// Only set parent context as parent MessageSource if no parent MessageSource
// registered already.
hms.setParentMessageSource(getInternalParentMessageSource());
}
}
if (logger.isTraceEnabled()) {
logger.trace("Using MessageSource [" + this.messageSource + "]");
}
}
else {
// Use empty MessageSource to be able to accept getMessage calls.
//使用DelegatingMessageSource作为国际化资源处理bean
DelegatingMessageSource dms = new DelegatingMessageSource();
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
if (logger.isTraceEnabled()) {
logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
}
}
}
简单的例子：
在application.properties配置如下信息：
logging.config=classpath:logback.xml
my.love=java
@Configuration
@PropertySource("classpath:/application.properties")
public class MessageConfiguration {
@Bean("messageSource")
public ReloadableResourceBundleMessageSource getReloadableResourceBundleMessageSource() {
ReloadableResourceBundleMessageSource rms = new ReloadableResourceBundleMessageSource();
rms.setBasename("message");
return rms;
}
}
@MyComponetAnno
public class MessageBean {
@Autowired
private ApplicationContext applicationContext;
public MessageBean() {
System.out.println("-----------------Abean 被实例化了。。。。。。。。。");
}
public void doSomething() {
System.out.println(this + " do something .....my.love="
+ this.applicationContext.getEnvironment().getProperty("my.love"));
System.out
.println("-----------project.name=" +
this.applicationContext.getMessage("project.name", null, Locale.CHINA));
}
}
public class MessageStarter {
public static void main(String[] args) {
// 注解方式，指定扫描的包
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
"edu.demo.spring.message");
MessageBean bean = context.getBean(MessageBean.class);
bean.doSomething();
context.close();
}
}
输出如下：
initApplicationEventMulticaster方法
下面就是初始化事件多播器：
/**
* 初始化ApplicationEventMulticaster.
* Uses SimpleApplicationEventMulticaster if none defined in the context.
* @see org.springframework.context.event.SimpleApplicationEventMulticaster
*/
protected void initApplicationEventMulticaster() {
//获取bean工厂
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
//如果bean工厂中包含applicationEventMulticaster，就使用它
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isTraceEnabled()) {
logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
//使用SimpleApplicationEventMulticaster
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
if (logger.isTraceEnabled()) {
logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +
"[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
}
}
}
onRefresh方法
没有子类进行实现
/**
* Template method which can be overridden to add context-specific refresh work.
* Called on initialization of special beans, before instantiation of singletons.
* <p>This implementation is empty.
* @throws BeansException in case of errors
* @see #refresh()
*/
protected void onRefresh() throws BeansException {
// For subclasses: do nothing by default.
}
registerListeners方法
接下来，检查事件监听器，并注册到事件传播器上
/**
* 在不生成Bean对象的情况下添加ApplicationListener bean作为监听器
* Add beans that implement ApplicationListener as listeners.
* Doesn't affect other listeners, which can be added without being beans.
*/
protected void registerListeners() {
// Register statically specified listeners first.
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let post-processors apply to them!
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// Publish early application events now that we finally have a multicaster...
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (!CollectionUtils.isEmpty(earlyEventsToProcess)) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
事件广播器执行的方法：
SimpleApplicationEventMulticaster的multicastEvent(ApplicationEvent, ResolvableType)方法：
@Override
public void multicastEvent(ApplicationEvent event) {
multicastEvent(event, resolveDefaultEventType(event));
}
@Override
public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
Executor executor = getTaskExecutor();
for (ApplicationListener<?> listener : getApplicationListeners(event, type)) {
if (executor != null) {
executor.execute(() -> invokeListener(listener, event));
}
else {
invokeListener(listener, event);
}
}
}
finishBeanFactoryInitialization方法
完成bean工厂的初始化，将bean工厂中，非懒加载的单例bean进行实例化
这一部分将在后面的文章中进行分析
/**
* Finish the initialization of this context's bean factory,
* initializing all remaining singleton beans.
*/
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(
beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
// Register a default embedded value resolver if no bean post-processor
// (such as a PropertyPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();
}
finishRefresh方法
/**
* Finish the refresh of this context, invoking the LifecycleProcessor's
* onRefresh() method and publishing the
* {@link org.springframework.context.event.ContextRefreshedEvent}.
*/
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
//清除缓存
clearResourceCaches();
// Initialize lifecycle processor for this context.
//初始化容器的生命周期处理器
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
//将刷新传播到生命周期处理器
getLifecycleProcessor().onRefresh();
// Publish the final event.
//发布最终事件
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
容器的关闭：
AbstractApplicationContext#close
AbstractApplicationContext#registerShutdownHook
AbstractApplicationContext#doClose
整体流程图如下：