前言
要是一上来就看 refresh 方法容易绕晕 , 再看源码之前 , 大家可以先去了解一下 context 和 beanFactory 的功能作用.
概述
上一节我们通过注解的方式将扫描到的 bean 信息都放在了 context 中了 ，那么本节我们开始介绍 refresh 方法。该方法也是生成 bean 的重要方法。 上一节我们讲到 ：
public AnnotationConfigApplicationContext(DefaultListableBeanFactory beanFactory) {
super(beanFactory);
this.reader = new AnnotatedBeanDefinitionReader(this);
this.scanner = new ClassPathBeanDefinitionScanner(this);
}
/**
* Create a new AnnotationConfigApplicationContext, deriving bean definitions
* from the given component classes and automatically refreshing the context.
* @param componentClasses one or more component classes — for example,
* {@link Configuration @Configuration} classes
*/
public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
this();
register(componentClasses);
refresh();
}
/**
* Create a new AnnotationConfigApplicationContext, scanning for components
* in the given packages, registering bean definitions for those components,
* and automatically refreshing the context.
* @param basePackages the packages to scan for component classes
*/
public AnnotationConfigApplicationContext(String... basePackages) {
this();
scan(basePackages);
refresh();
}
构造方法最后都会走到 refresh 方法 ， 我依然要放出这张图， 该图有利于理解我们了解spring 生成 bean 的过程 。我们知道 bean 可以通过 xml 文件方式注入 , 也可以通过注解的方式注入 , 下面是 AnnotationConfigApplicationContext 和 ClassPathXmlApplicationContext 两个类的继承结构图 , 可以看到 AbstractApplicationContext 这个可以说是逻辑抽象类 , 从文章后边讲的 refresh 方法也可以知道.
而 AbstractApplicationContext 中有个 抽象方法返回一个 ConfigurableListableBeanFactory 对象 , 这个对象的作用是对类的管理和初始化. 我们甚至可以说 context 类是集大成者 , 而 beanFactory 从名字也可以看出是bean 相关的管家 .
划重点 :
-
context 类是集大成者 -
beanFactory 从名字也可以看出是bean 相关的管家 .
记住这两点有助于我们学习 生成 bean 的过程 , 不然容易被后面的逻辑绕晕.
refresh 方法
refresh 方法不是 AnnotationConfigApplicationContext 类的方法 ，而是父类的方法 ， 位于org.springframework.context.support.AbstractApplicationContext#refresh
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
// 这个 beanFactory 对象很重要 , 后面很多 bean 逻辑都是在这个类完成的.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
//在 context 的子类实现，父类方法为空方法
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
// 实例化 并 执行 之前已经注册了的各种 BeanFactoryPostProcessor
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
//这里的注册，是指把实例化的BeanPostProcessor存到beanFactory的某个list中
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
// 空方法子类实现
onRefresh();
// Check for listener beans and register them.
// 检查 listener 并注册他们
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
// 初始化剩下的单例类
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
// 发布对应的时间
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
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();
}
}
}
可以看到 refresh 方法不长 ,但是每个方法调用下去很容易绕晕, 我们先总结一下 refresh 主要做了什么事吧
- 前期准备；记录了容器启动时间；容器状态；刷新一些在此方法之前就可能已经存在的监听器
- 空方法，用于子类扩展功能
- 实例化并执行之前已经注册了的各种BeanFactoryPostProcessor (核心)
- 实例化 拦截bean创建的处理器BeanPostProcessor；(核心)
- 初始化容器的MessageSource类型的bean，MessageSource用于解析消息
- 初始化容器的事件广播
- 空方法，在特定的子类中 初始化其他特殊bean
- 注册实现了ApplicationListener接口的监听者
- 实例化剩下的单例bean，完成全部bean的实例化，除了懒加载的 (核心)
- 最后一步，完成此刷新方法，发布完成事件
我们浓缩一下和 bean 相关的最核心的重要步骤 :
- 实例化 并 执行 之前已经注册了的各种 BeanFactoryPostProcessor
- 调用 getBean 方法
还有一点大家需要注意的是我们看到refresh 中调用的方法都会把 beanFactory 传过去 , 足以说明了 beanFactory 的功能和重要性 !!!
prepareRefresh
org.springframework.context.support.AbstractApplicationContext#prepareRefresh
/**
* Prepare this context for refreshing, setting its startup date and
* active flag as well as performing any initialization of property sources.
*/
protected void prepareRefresh() {
// Switch to active.
this.startupDate = System.currentTimeMillis();
this.closed.set(false);
this.active.set(true);
if (logger.isDebugEnabled()) {
if (logger.isTraceEnabled()) {
logger.trace("Refreshing " + this);
}
else {
logger.debug("Refreshing " + getDisplayName());
}
}
// Initialize any placeholder property sources in the context environment.
initPropertySources();
// Validate that all properties marked as required are resolvable:
// see ConfigurablePropertyResolver#setRequiredProperties
getEnvironment().validateRequiredProperties();
// 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<>();
}
- 设置Spring容器的启动时间，
- 开启活跃状态，撤销关闭状态，。
- 初始化context environment（上下文环境）中的占位符属性来源。
- 验证环境信息里一些必须存在的属性
obtainFreshBeanFactory
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
这一行代码 , 需要注意一下 , obtainFreshBeanFactory 这个方法会返回一个 ConfigurableListableBeanFactory 对象 , 该对象继承 BeanFactory , 而实际上 Context 关于 Bean 相关的逻辑都是 BeanFactory 来完成 .
/**
* Tell the subclass to refresh the internal bean factory.
* @return the fresh BeanFactory instance
* @see #refreshBeanFactory()
* @see #getBeanFactory()
*/
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
return getBeanFactory();
}
/**
* Subclasses must return their internal bean factory here. They should implement the
* lookup efficiently, so that it can be called repeatedly without a performance penalty.
* <p>Note: Subclasses should check whether the context is still active before
* returning the internal bean factory. The internal factory should generally be
* considered unavailable once the context has been closed.
* @return this application context's internal bean factory (never {@code null})
* @throws IllegalStateException if the context does not hold an internal bean factory yet
* (usually if {@link #refresh()} has never been called) or if the context has been
* closed already
* @see #refreshBeanFactory()
* @see #closeBeanFactory()
*/
@Override
public abstract ConfigurableListableBeanFactory getBeanFactory() throws IllegalStateException;
prepareBeanFactory
我们得到的 BeanFactory 需要初始化很多参数 , 包括 BPP (BeanPostProcessor)
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
//设置BeanFactory的类加载器
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
//设置支持表达式解析器
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
//添加部分BeanPostProcessor【ApplicationContextAwareProcessor】, 回调
// Configure the bean factory with context callbacks.
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.
//注册可以解析的自动装配；我们能直接在任何组件中自动注入：BeanFactory、ResourceLoader、ApplicationEventPublisher、ApplicationContext
//其他组件中可以通过 @autowired 直接注册使用
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.
// 添加部分BeanPostProcessor【ApplicationListenerDetector】,作用: 发现早期内部的 bean
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.
// 注册默认的环境 beans , 可以看到是先会去判断是否是 beanFactory 本身创建的 bean ,例如 springboot 中我们有些场景下会去使用使用自己的 bean ,而不是默认的 environment bean ,不存在再去注册
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
postProcessBeanFactory
空方法 , 子类实现
/**
* 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
/**
* 注意哦，这里传进来的 beanFactoryPostProcessors 是来自 AbstractApplicationContext ，
* 该方法会调用 所有的 BeanFactoryPostProcessor 的回调方法，回调方法指的是 BeanPostProcessor 的接口的接口方法（用于回调）
*/
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;
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
//先处理 BeanDefinitionRegistryPostProcessor
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
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.
// 翻译上边：这里先不初始化FactoryBeans，我们需要保留所有常规bean的状态为非初始化状态，好让post-processors能对它们发挥作用
//实现了PriorityOrdered, Ordered或者其他接口的，要分开处理。
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
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);
//该方法最终会调用 BeanDefinitionRegistryPostProcessor 的 postProcessBeanDefinitionRegistry 接口方法，该方法就是执行后置器的逻辑，例如 ConfigurationClassPostProcessor 的 postProcessBeanDefinitionRegistry 处理配置bean 的逻辑，我们在后续再分析
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
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();
//在这个处理过程中，可能会有新的bean被spring发现，并注册到容器中。
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
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();
}
// 调用剩下没有调用过的 processors 的回调方法
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
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.
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.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
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.
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...
beanFactory.clearMetadataCache();
}
重点看一下 PostProcessorRegistrationDelegate 的 invokeBeanFactoryPostProcessors 静态方法 。
BeanFactoryPostProcessor总共有两种：
1.BeanFactoryPostProcessor
2.BeanDefinitionRegistryPostProcessor，它继承了第一种。
整体上流程如下：
- 处理BeanDefinitionRegistryPostProcessor
1.1 处理PriorityOrdered优先级的
1.2 处理Ordered优先级的
1.3 处理其他优先级的
- 处理BeanFactoryPostProcessor
2.1 处理PriorityOrdered优先级的
2.2 处理Ordered优先级的
2.3 处理其他优先级的
题外话 -- BeanDefinitionRegistryPostProcessor 和 BeanFactoryPostProcessors
public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {
/**
* Modify the application context's internal bean definition registry after its
* standard initialization. All regular bean definitions will have been loaded,
* but no beans will have been instantiated yet. This allows for adding further
* bean definitions before the next post-processing phase kicks in.
*
* 作用 : This allows for adding further
* bean definitions (bean 定义) before the next post-processing phase kicks in
*
* @param registry the bean definition registry used by the application context
* @throws org.springframework.beans.BeansException in case of errors
*/
void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;
}
BeanDefinitionRegistryPostProcessor 继承 BeanFactoryPostProcessor , 我找了了它的一个实现类, org.springframework.context.annotation.ConfigurationClassPostProcessor , 最终会调用以下方法 ,作用是解析带有`@Configuration 的类
/**
* Build and validate a configuration model based on the registry of
* {@link Configuration} classes.
*/
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
....
// Parse each @Configuration class
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
do {
StartupStep processConfig = this.applicationStartup.start("spring.context.config-classes.parse");
parser.parse(candidates);
parser.validate();
Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
configClasses.removeAll(alreadyParsed);
// 看这里 !!!! 读取 model , 根据内容创建对应的 bean d
// Read the model and create bean definitions based on its content
if (this.reader == null) {
this.reader = new ConfigurationClassBeanDefinitionReader(
registry, this.sourceExtractor, this.resourceLoader, this.environment,
this.importBeanNameGenerator, parser.getImportRegistry());
}
this.reader.loadBeanDefinitions(configClasses);
alreadyParsed.addAll(configClasses);
processConfig.tag("classCount", () -> String.valueOf(configClasses.size())).end();
candidates.clear();
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
Set<String> alreadyParsedClasses = new HashSet<>();
for (ConfigurationClass configurationClass : alreadyParsed) {
alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
}
for (String candidateName : newCandidateNames) {
if (!oldCandidateNames.contains(candidateName)) {
BeanDefinition bd = registry.getBeanDefinition(candidateName);
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
!alreadyParsedClasses.contains(bd.getBeanClassName())) {
candidates.add(new BeanDefinitionHolder(bd, candidateName));
}
}
}
candidateNames = newCandidateNames;
}
}
while (!candidates.isEmpty());
// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
}
if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
// Clear cache in externally provided MetadataReaderFactory; this is a no-op
// for a shared cache since it'll be cleared by the ApplicationContext.
((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
}
}
registerBeanPostProcessors
位置 : PostProcessorRegistrationDelegate#registerBeanPostProcessors BeanPostProcessor的作用是拦截bean创建，也就是在bean实例化的时候（实例化前后），能插入一些额外的动作 , 有点像拦截器的作用 .
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
//实例化一个BeanPostProcessorChecker，用于记录日志信息，比如当一个bean没有被任何后置处理器处理时
//BeanPostProcessorChecker是一个内部类，实现了BeanPostProcessor接口
// 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));
//这里也分为PriorityOrdered,Ordered, and 其他 3中情况分开处理；所以先遍历一遍，把类型分开；
//遍历时候，顺便把PriorityOrdered实例化了
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
//内部使用的 PostProcessors
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
//没有顺序的 PostProcessors
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).
// 当前的 PostPocessors 见下图，这里重新注册 post-processor 作为 ApplicationListeners 用于发现内部的 beans
// 放在 processor 处理端的尾部 , 用于获取代理等.
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
/**
* Register the given BeanPostProcessor beans.
*/
private static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {
if (beanFactory instanceof AbstractBeanFactory) {
// Bulk addition is more efficient against our CopyOnWriteArrayList there
((AbstractBeanFactory) beanFactory).addBeanPostProcessors(postProcessors);
}
else {
for (BeanPostProcessor postProcessor : postProcessors) {
beanFactory.addBeanPostProcessor(postProcessor);
}
}
}
public void addBeanPostProcessors(Collection<? extends BeanPostProcessor> beanPostProcessors) {
this.beanPostProcessors.removeAll(beanPostProcessors);
this.beanPostProcessors.addAll(beanPostProcessors);
}
可以看到注册 BeanPostProcessors 的逻辑主要就是加入到一个列表中去.
initMessageSource
MessageSource用于解析消息 , 提供了若干获取消息的方法 .
/**
Strategy interface for resolving messages, with support for the parameterization and internationalization of such messages.
Spring provides two out-of-the-box implementations for production:
**/
public interface MessageSource {
@Nullable
String getMessage(String code, @Nullable Object[] args, @Nullable String defaultMessage, Locale locale);
String getMessage(String code, @Nullable Object[] args, Locale locale) throws NoSuchMessageException;
String getMessage(MessageSourceResolvable resolvable, Locale locale) throws NoSuchMessageException;
}
可以从接口的注释看到 MessageSource 是一个用于可以对信息国际化和参数化的接口 . spring 提供了 两个开箱即用的现实 : ResourceBundleMessageSource 和 ReloadableResourceBundleMessageSource
/**
* Initialize the MessageSource.
* Use parent's if none defined in this context.
*/
protected void initMessageSource() {
// getBeanFactory 是个抽象方法 , 这个方法太秒了 !!! 剧透一下我们下一节就可以讲到真正获取 bean 的地方 , 其中就会需要
// 一个 ConfigurableListableBeanFactory 对象 ,而这个对象就是由 这个抽象方法返回的! 我们下一节再讲 .
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 当前的这个 beanFactory 是否包含这么一个 MessageSource , 没有就创建咯
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
// Make MessageSource aware of parent 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.
DelegatingMessageSource dms = new DelegatingMessageSource();
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
// 单例注册上去
beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
if (logger.isTraceEnabled()) {
logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
}
}
}
getBeanFactory 方法对获取 bean 非常重要 ,我们将会在下一节进行介绍 .
initApplicationEventMulticaster
从名字就可以知道是初始化事件广播.
/**
* Initialize the ApplicationEventMulticaster.
* Uses SimpleApplicationEventMulticaster if none defined in the context.
* @see org.springframework.context.event.SimpleApplicationEventMulticaster
*/
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
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 {
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() + "]");
}
}
}
代码也没高深的逻辑 , 和 initMessageSource 方法很像.
onRefresh
/**
* 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.
}
当前类为空方法 , 具体逻辑交给子类实现 .
registerListeners
注册监听事件
/**
* 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);
}
}
}
没什么复杂的逻辑
finishBeanFactoryInitialization
完成剩下的 (不是 lazy-init) bean 初始化
- 获取所有的beanDefinitionNames，然后遍历
- 先合并其父类的相关公共属性,返回合并的RootBeanDefinition
- 如果不是抽象类,而且是非懒加载的单例则开始创建Bean
- 首先判断是不是FactoryBean，如果是FactoryBean,使用 &+beanName ,去获取 FactoryBean
- 如果不是FactoryBean，则直接调用getBean(beanName);方法创建或者获取对应的Bean
SmartInitializingSingleton是Spring4.1版本之后的一个新扩展点。在创建完所有的非懒加载单例Bean之后，调用SmartInitializingSingleton接口，完成回调。
我们例子中的 MyService 最终会调用 getBean 来完成初始化
getBean 方法会在下一篇讲到 .
finishRefresh
/**
* Finish the refresh of this context, invoking the LifecycleProcessor's
* onRefresh() method and publishing the
*
* 完成 context 的 refresh 方法， 调用 LifecycleProcessor 的 onRefresh() 方法，并发布事件
*
* {@link org.springframework.context.event.ContextRefreshedEvent}.
*/
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
clearResourceCaches();
// Initialize lifecycle processor for this context.
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
getLifecycleProcessor().onRefresh();
// Publish the final event.
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
参考资料
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