目标
追踪下面一段代码的流程：
AnnotationConfigApplicationContextDemo
/**
* description
* date 2021-06-30 11:21
**/
public class AnnotationConfigApplicationContextDemo {
public static void main(String[] args) {
final AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(SimpleConfig.class);
User user = applicationContext.getBean(User.class);
System.out.println("user:" + user);
}}
Configuration
public class SimpleConfig {
Bean
public User user(){
return new User("xgimi", 10);
}}
public class User {
private String name;
private Integer age;
...
流程
核心逻辑都在AnnotationConfigApplicationContext的带参构造器中：
public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
this();
register(componentClasses);
refresh();
}
空构造器做了什么
先说答案： 两个事情，一是创建了BedefinitionReader、BeanDefinitionScanner，提供了扫描BeanDefinition的能力； 二是通过父类GenericApplicationContext的构造器创建了DefaultListableBeanFactory，提供底层的IOC能力。
初始化AnnotatedBeanDefinitionReader
public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry) {
//注入registry，并且初始化Environment对象
this(registry, getOrCreateEnvironment(registry));
}
提供注册beanDefinition的能力
public AnnotationConfigApplicationContext() {
StartupStep createAnnotatedBeanDefReader = this.getApplicationStartup().start("spring.context.annotated-bean-reader.create");
this.reader = new AnnotatedBeanDefinitionReader(this);
createAnnotatedBeanDefReader.end();
this.scanner = new ClassPathBeanDefinitionScanner(this);
}
我们会在后面探究BeanDefinitionRegistry注册BeanDefinition的本质
获取环境对象 getOrCreateEnvironment这个方法进行页游的内部环境的创建并获取：
private static Environment getOrCreateEnvironment(BeanDefinitionRegistry registry) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
if (registry instanceof EnvironmentCapable) {
return ((EnvironmentCapable) registry).getEnvironment();
}
return new StandardEnvironment();
}
环境对象中包含了系统环境变量，自定义属性等内容。
通过构造器可以看到，AnnotatedBeanDefinitwww.sangpi.comionReader底层维护了一个BeanDefinitionRegistry。实际上，他就是通过BeanDefinitionRegistry提供的注册能力，而AnnotationConfigApplicationContext本身就是一个BeanDefinitionRegistry；所以在调用AnnotatedBeanDefinitionReader构造器时，我们传入的就是AnnotationConfigApplicationContext：
实际上是组合关系，AnnotationConfigApplicationContext中大部分的能力，包括注册beanDefinition，依赖查找，依赖注入，都是通过DefaultListableBeanFactory通过的底层能力支持。
如何将配置类注册为BeanDefinition
在AnnotationConfigApplicationContext中：
Override
public void register(Class<?>... componentClasses) {
Assert.notEmpty(componentClasses, "At least one component class must be specified");
StartupStep registerComponentClass = this.getApplicationStartup().start("spring.context.component-classes.register")
.tag("classes", () -> Arrays.toString(componentClasses));
//注册配置类
this.reader.register(componentClasses);
registerComponentClass.end();
}
从上面代码可以看出，主要是调用了reader的register方法完成的注册，来看下这个方法的实现逻辑
public void register(Class<?>... componentClasses) {
for (Class<?> componentClass : componentClasses) {
registerBean(componentClass);
}
}
public void registerBean(Class<?> beanClass) {
doRegisterBean(beanClass, null, null, null, null);
}
private <T> void doRegisterBean(Class<T> beanClass, @Nullable String name,
@Nullable Class<? extends Annotation>[] qualifiers, @Nullable Supplier<T> supplier,
@Nullable BeanDefinitionCustomizer[] customizers) {
//进来就先把class对象转为一个BeanDefinition，此时这个BeanDefinition中只有class信息和注解类上注解信息
AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass);
//处理@Conditional注解
if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
return;
}
//supplier会优先于所有的构造器和工厂方法进行类的实例化，但是不会影响属性设置
abd.setInstanceSupplier(supplier);
//处理scope，没有设置，默认返回singleton；@Scope("scopeName")会在这个方法中进行处理，获得scopeName
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
abd.setScope(scopeMetadata.getScopeName());
//创建beanName AnnotationBeanNameGenerator提供能力，但以接口入参为优先
String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
//将以下几个注解标注的值设置到abd中
//1.@Lazy 2.@Primary 3.@Role 4.@DependesOn 5.@Description
AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
if (qualifiers != null) {
for (Class<? extends Annotation> qualifier : qualifiers) {
if (Primary.class == qualifier) {
abd.setPrimary(true);
}
else if (Lazy.class == qualifier) {
abd.setLazyInit(true);
}
else {
abd.addQualifier(new AutowireCandidateQualifier(qualifier));
}
}
}
if (customizers != null) {
for (BeanDefinitionCustomizer customizer : customizers) {
customizer.customize(abd);
}
}
//definitionHolder 保存的是beanDefinition和beanName(还可以有别名)
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
//如果@Scope设置了代理，这里将会返回一个代理对象
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
//将definitionHolder中的beanDefinition注册到registry对象中
//DefaultListableBeanFactory.registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
//最后的结果：DefaultListableBeanFactory中的beanDefinitionMap中存入一个beanDefinition，beanDefinitionNames中存入beanName
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
}
综合上述代码，整理以下doRegisterBean的大致逻辑：
创建一个配置类对象的AnnotationBeanDefinition
通过AnnotationBeanDefinition解析类上面是否存在Conditional注解，并判断是否满足注册的条件，如果不满足，则不进行注册
向abd中注册方法入参传入的 Supplier，后续可通过该接口实现bean的实例化
解析Scope属性并注册到abd中
创建beanName
创建一个beanDefinitionHolder保存abd和beanName，alias之间的对应关系
处理非单例Scope，返回一个代理，详见Scope的处理过程
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
我们来看下第9步，究竟是如何注册的：
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
public static void registerBeanDefinition( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
//TODO
registry.registerAlias(beanName, alias);
}
}
}
可以看到，实际进行了两部分注册：
注册beanName
注册别名
结果发现还是使用的DefaultListableBeanFactory进行注册的，这也论证了我们上面关于DefaultListableBeanFactory和AnnotationConfigApplicationContext之间关系的结论。来看看DefaultListableBeanFactory中究竟是怎么实现的吧：
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
Assert.hasText(beanName, "Bean name must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isInfoEnabled()) {
logger.info("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
existingDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(existingDefinition)) {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
removeManualSingletonName(beanName);
}
}
else {
// Still in startup registration phase// 主要看这里
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
else if (isConfigurationFrozen()) {
clearByTypeCache();
}
}
上述的代码，先检查了容器中是否已经注册过了该bd，再检查了是否正在注册该db；而我们是第一次注册，所以走的核心分支就是第59行开始的else分支。做了下面几件事情：
向beanDefinitionMap中放入了beanName为key的beanDefinition
向beanDefinitionNames中放入了beanName
如果manualSingletonNames中存在beanName，将其移除
为什么要单独维护一个beanDefinitionNames？主要是因为beanDefinitionMap是无序的，而beanDefinitionNames是一个ArrayList，是有序的，可以保存bd的注册顺序
refresh方法都做了什么
1.prepareRefresh
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.
//非web环境下默认是空的实现
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<>();
}
预刷新阶段主要做了一下几件事情：
提供initPropertySources()扩展方法供容器进行外部资源加载，在AnnotationContextApplicationContext中默认是空实现
getEnvironment().validateRequiredProperties();进行必填属性的校验，是AbstractPropertyResolver这个接口提供的能力，Environment对象是这个接口的实现。
@Override
public void validateRequiredProperties() {
MissingRequiredPropertiesException ex = new MissingRequiredPropertiesException();
for (String key : this.requiredProperties) {
if (this.getProperty(key) == null) {
ex.addMissingRequiredProperty(key);
}
}
if (!ex.getMissingRequiredProperties().isEmpty()) {
throw ex;
}
}
默认容器中是没有必须存在的属性的，如果需要添加该校验，则通过beanFactory获取到Environment，然后再进行设置：
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
applicationContext.register(SimpleConfig.class);
applicationContext.getEnvironment().setRequiredProperties("system");
applicationContext.refresh();
实际上是调用的AbstractPropertyResolver类的下面方法
//设置必须存在的属性
@Override
public void setRequiredProperties(String... requiredProperties) {
Collections.addAll(this.requiredProperties, requiredProperties);
}
requiredProperties是一个LinkedHashSet
private final Set<String> requiredProperties = new LinkedHashSet<>();
在容器中创建earlyApplicationListeners、earlyApplicationEvents
2.obtainFreshBeanFactory
通过该方法的返回值可以判断他就是获取了容器中内置的ConfigurableListableBeanFactory，我们来看他具体是怎么获取的：
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
return getBeanFactory();
}
其中：getBeanFactory()方法是很好理解的，他就是把GenericApplicationContext中保存的DefaultListableBeanFactory返回，这个DefaultListableBeanFactor是在GenericApplicationContext的空构造器中实例化的。 我们看下refreshBeanFactory()中做了什么：
@Override
protected final void refreshBeanFactory() throws IllegalStateException {
//内部容器只允许refresh一次
if (!this.refreshed.compareAndSet(false, true)) {
throw new IllegalStateException(
"GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
}
this.beanFactory.setSerializationId(getId());
}
主要是对refreshed进行了cas修改，以保证容器只会被刷新一次
3.prepareBeanFactory(beanFactory)
容器的准备阶段
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
if (!shouldIgnoreSpel) {
//设置el表达式解析器（#{...}）
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
}
//设置属性解析器PropertyEditorRegistrar
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
//为容器中添加一个ApplicationContextAwareProcessor，这是容器中添加的第一个BeanPostProcessor
//ApplicationContextAwareProcessor的作用：
//判断bean是否实现了下面的Aware接口，如果实现了，这把相应的内建bean或单例对象赋给该bean
//1.EnvironmentAware -> applicationContext.getEnvironment()
//2.EmbeddedValueResolverAware -> embeddedValueResolver
//3.ResourceLoaderAware -> applicationContext
//4.ApplicationEventPublisherAware -> applicationContext
//5.MessageSourceAware -> applicationContext
//6.ApplicationContextAware -> applicationContext
//7.ApplicationStartupAware -> applicationContext.getApplicationStartup()
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.ignoreDependencyInterface(ApplicationStartupAware.class);
//添加容器内建依赖
// BeanFactory interface not registered as resolvable type in a plain factory.
// MessageSource registered (and found for autowiring) as a 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.
// 处理实现了ApplicationListener接口的bean
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (!NativeDetector.inNativeImage() && 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.
// 在beanFactory中注入下面的单例对象
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());
}
if (!beanFactory.containsLocalBean(APPLICATION_STARTUP_BEAN_NAME)) {
beanFactory.registerSingleton(APPLICATION_STARTUP_BEAN_NAME, getApplicationStartup());
}
}设置ClassLoader
设置el表达式解析器
设置PropertyEditorRegistrar
添加一个ApplicationContextAwareProcessor判断bean是否实现了下面的Aware接口，如果实现了，这把相应的内建bean或单例对象赋给该bean 1.EnvironmentAware -> applicationContext.getEnvironment() 2.EmbeddedValueResolverAware -> embeddedValueResolver 3.ResourceLoaderAware -> applicationContext 4.ApplicationEventPublisherAware -> applicationContext 5.MessageSourceAware -> applicationContext 6.ApplicationContextAware -> applicationContext 7.ApplicationStartupAware -> applicationContext.getApplicationStartup()
ignoreDependencyInterface：在自动装配时忽略下面这些接口，实现了下述接口，可以通过set方法接受aware回调传入的值进行装配
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.ignoreDependencyInterface(ApplicationStartupAware.class);
添加容器内建依赖。容器的内建依赖会保存在resolvableDependencies，支持通过类型进行依赖注入，主要解决的问题是同一种类型存在多个依赖对象，spring在自动装配的时候会报错，但是如果在resolvableDependencies中指定了具体类型的装配对象，则直接可以使用指定对象。spring容器中存在多个BeanFactory等类型的对歌对象，所以这里将其依赖对象指定，避免报错。我们也可以通过自定义BeanFactoryPostProcessor获取Beanfactory，然后指定自己的类型-依赖对象关系。
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
添加ApplicationListenerDetector，DestructionAwareBeanPostProcessor：bean曝光前回调，在对外提供bean实例之前，可以返回代理对象替换beanMergedBeanDefinitionPostProcessor
class ApplicationListenerDetector implements DestructionAwareBeanPostProcessor, MergedBeanDefinitionPostProcessor {
直接注册四个单例对象
// Register default environment beans.
// 在beanFactory中注入下面的单例对象
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());
}
if (!beanFactory.containsLocalBean(APPLICATION_STARTUP_BEAN_NAME)) {
beanFactory.registerSingleton(APPLICATION_STARTUP_BEAN_NAME, getApplicationStartup());
}4.postProcessBeanFactory
预留的扩展方法，默认没有实现
5.invokeBeanFactoryPostProcessors(beanFactory)
关于BeanFactoryPostProcesso，我们先了解下面两点：
注册BeanFactoryPostProcessor：ConfigurableApplicationContext#addBeanFactoryPostProcessor
BeanFactoryPostProcessor的作用：
@FunctionalInterface
public interface BeanFactoryPostProcessor {
/**
* 在所有beanDefinition已经加载，且没有Bean实例化之前，修改application的内置beanFactory
* 该方法可以支持修改beanDefinition的属性配置，甚至可以提前初始化bean
* 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 overriding or adding
* properties even to eager-initializing beans.
* @param beanFactory the bean factory used by the application context
* @throws org.springframework.beans.BeansException in case of errors
*/
void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;}
简而言之，就是在第3步将内置beanfactory准备完毕之后。给用户一次机会再获取到beanFactory 接下来我们研究invokeBeanFactoryPostProcessors的流程，这里默认容器中是不会注册BeanFactoryPostProcessor的，但是这个方法还有其他的作用
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
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 (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
getBeanFactoryPostProcessors()
public List<BeanFactoryPostProcessor> getBeanFactoryPostProcessors() {
return this.beanFactoryPostProcessors;
}
PostProcessorRegistrationDelegate
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// WARNING: Although it may appear that the body of this method can be easily
// refactored to avoid the use of multiple loops and multiple lists, the use
// of multiple lists and multiple passes over the names of processors is
// intentional. We must ensure that we honor the contracts for PriorityOrdered
// and Ordered processors. Specifically, we must NOT cause processors to be
// instantiated (via getBean() invocations) or registered in the ApplicationContext
// in the wrong order.
//
// Before submitting a pull request (PR) to change this method, please review the
// list of all declined PRs involving changes to PostProcessorRegistrationDelegate
// to ensure that your proposal does not result in a breaking change:
// %3Aclosed+label%3A%22status%3A+declined%22
// 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<>();
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.
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);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
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, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// 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, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
}
// 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();
}
主要流程：
创建两个list分别保存BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor
将自定义注册的BeanFactoryPostProcessor按照类型分别存入regularPostProcessors或者registryProcessors，并且：如果是BeanDefinitionRegistryPostProcessor，则直接调用其postProcessBeanDefinitionRegistry方法
创建一个新的列表来保存容器内置的BeanDefinitionRegistryPostProcessor
通过BeanDefinitionRegistryPostProcessor类型以及PriorityOrdered获取容器中对对应的bean，放入currentRegistryProcessors，并将名字放入processedBeans，表示已经执行。这里会得到一个：org.springframework.context.annotation.internalConfigurationAnnotationProcessor
将currentRegistryProcessors排序，并且放入registryProcessors
遍历执行currentRegistryProcessors中的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法
这里会执行internalConfigurationAnnotationProcessor的回调方法，这个类后续会专项研究，其结果就是把配置类中Bean方法对应的类加载到容器中注册为bd
清空currentRegistryProcessors
重复4-8，调用的是实现了Ordered接口的BeanDefinitionRegistryPostProcessor
重复4-8，调用没有实现排序接口的BeanDefinitionRegistryPostProcessor
通过上面的操作，所有的BeanDefinitionRegistryPostProcessor都加入了registryProcessors，所有的自定义BeanFactoryPostProcessor都加入了regularPostProcessors。执行他们的postProcessBeanFactory方法
现在还有容器内置的BeanFactoryPostProcessor没有处理，也按照PriorityOrdered，Ordered，nonOrdered的顺序依次加载并调用他们的postProcessBeanFactory方法
6.initMessageSource
MessageSource列为专题讨论
7.initApplicationEventMulticaster()
事件广播机制列为专题讨论
8.onRefresh
截止到这里，整个beanfactory已经准备就绪了。剩下的就是容器中的bean的处理了，再此之前，可以通过onFresh方法执行回调。例如在SpringBoot中，就是通过这个方法进行的嵌入式web容器启动
9.registerListeners()
注册容器内置的listener
注册实现了ApplicationListener接口的类
10.inishBeanFactoryInitialization(beanFactory)
实例化所有非懒加载的单例bean 这个流程又是非常复杂的逻辑，我们放在第二章进行讨论
总结
经过上述的步骤，spring容器已经初始化完成，beanFactory准备就绪。ApplicatiionContext提供的扩展特性：事件机制，资源，AOP等能力也已经初始化完成