前面两篇文章分析了super(this)和setConfigLocations(configLocations)的源代码，本文来分析下refresh的源码，
Spring加载流程源码分析01【super】
Spring加载流程源码分析02【setConfigLocations】
先来看下ClassPathXmlApplicationContext类的初始化过程：
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
refresh介绍
refresh方法的具体实现是在AbstractApplicationContext类中如下:
@Override
public void refresh() throws BeansException, IllegalStateException {
//startupShutdownMonitor对象在spring环境刷新和销毁的时候都会用到，确保刷新和销毁不会同时执行
synchronized (this.startupShutdownMonitor) {
// 准备工作，例如记录事件，设置标志，检查环境变量等，并有留给子类扩展的位置，用来将属性加入到applicationContext中
prepareRefresh();
// 创建beanFactory，这个对象作为applicationContext的成员变量，可以被applicationContext拿来用,
// 并且解析资源（例如xml文件），取得bean的定义，放在beanFactory中
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 对beanFactory做一些设置，例如类加载器、SPEL解析器、指定bean的某些类型的成员变量对应某些对象.
prepareBeanFactory(beanFactory);
try {
// 子类扩展用，可以设置bean的后置处理器（bean在实例化之后这些后置处理器会执行）
postProcessBeanFactory(beanFactory);
// 执行beanFactory后置处理器（有别于bean后置处理器处理bean实例，beanFactory后置处理器处理bean定义）
invokeBeanFactoryPostProcessors(beanFactory);
// 将所有的bean的后置处理器排好序，但不会马上用，bean实例化之后会用到
registerBeanPostProcessors(beanFactory);
// 初始化国际化服务
initMessageSource();
// 创建事件广播器
initApplicationEventMulticaster();
// 空方法，留给子类自己实现的，在实例化bean之前做一些ApplicationContext相关的操作
onRefresh();
// 注册一部分特殊的事件监听器，剩下的只是准备好名字，留待bean实例化完成后再注册
registerListeners();
// 单例模式的bean的实例化、成员变量注入、初始化等工作都在此完成
finishBeanFactoryInitialization(beanFactory);
// applicationContext刷新完成后的处理，例如生命周期监听器的回调，广播通知等
finishRefresh();
}
catch (BeansException ex) {
logger.warn("Exception encountered during context initialization - cancelling refresh attempt", ex);
// 刷新失败后的处理，主要是将一些保存环境信息的集合做清理
destroyBeans();
// applicationContext是否已经激活的标志，设置为false
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
}
}
接下来一一介绍下
1.prepareRefresh介绍
protected void prepareRefresh() {
// 设置初始化开始的时间
this.startupDate = System.currentTimeMillis();
// 设置context的关闭状态为false
this.closed.set(false);
// 设置context的活动状态是true
this.active.set(true);
if (logger.isInfoEnabled()) {
logger.info("Refreshing " + this);
}
// Initialize any placeholder property sources in the context environment
// 留个子类自己实现的空方法
initPropertySources();
// 验证对应的key在环境变量中是否存在，如果不存在就抛异常
getEnvironment().validateRequiredProperties();
// earlyApplicationEvents存放早起的一些事件。
this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();
}
initPropertySources() 留给子类实现的方法
protected void initPropertySources() {
// For subclasses: do nothing by default.
}
2.obtainFreshBeanFactory()介绍
创建了一个BeanFactory对象
/**
* Tell the subclass to refresh the internal bean factory.
* 子类实现
* @return the fresh BeanFactory instance
* @see #refreshBeanFactory()
* @see #getBeanFactory()
*/
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
// 子类(AbstractRefreshableApplicationContext)创建一个ConfigurableListableBeanFactory 对象
refreshBeanFactory();
// 获取refreshBeanFactory()实现类中创建的BeanFactory对象
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
refreshBeanFactory()
该方法是子类实现的方法，在AbstractRefreshableApplicationContext类中该方法创建了ConfigurableListableBeanFactory 对象并且完成了，并赋值给了beanFactory
@Override
protected final void refreshBeanFactory() throws BeansException {
// 如果BeanFactory存在就销毁
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
// BeanFactory的初始化操作
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
// 在次方法中完成了application.xml文件的解析
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
// 创建的对象赋值给了成员变量beanFactory
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
进入loadBeanDefinitions(beanFactory)方法查看
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setEnvironment(getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
initBeanDefinitionReader(beanDefinitionReader);
// 进入该方法查看
loadBeanDefinitions(beanDefinitionReader);
}
loadBeanDefinitions(beanDefinitionReader);
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws IOException {
String[] configLocations = getConfigLocations();
if (configLocations != null) {
for (String configLocation : configLocations) {
//继续进入 configLocation 是applicationContext.xml
reader.loadBeanDefinitions(configLocation);
}
}
}
进入跟踪
public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {
//这是我们在前面文章中初始的ResourceLoader对象
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
}
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
try {
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
// 此处进入
int loadCount = loadBeanDefinitions(resources);
if (actualResources != null) {
for (Resource resource : resources) {
actualResources.add(resource);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
}
return loadCount;
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"Could not resolve bean definition resource pattern [" + location + "]", ex);
}
}
else {
// Can only load single resources by absolute URL.
Resource resource = resourceLoader.getResource(location);
int loadCount = loadBeanDefinitions(resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
}
}
继续跟踪
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<EncodedResource>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
// 获取applicationContext.xml对应的字节输入流
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
// 将配置文件中的信息加载到定义的bean中
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
finally {
inputStream.close();
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}
跟踪到如下代码
try {
Document doc = doLoadDocument(inputSource, resource);
return registerBeanDefinitions(doc, resource);
}
上面是加载bean定义的关键代码：先制作Document对象，再调用registerBeanDefinitions方法，最终会将每个bean的定义放入DefaultListableBeanFactory的beanDefinitionMap中。
getBeanFactory()
获取refreshBeanFactory()实现类中创建的BeanFactory对象
@Override
public final ConfigurableListableBeanFactory getBeanFactory() {
synchronized (this.beanFactoryMonitor) {
if (this.beanFactory == null) {
throw new IllegalStateException("BeanFactory not initialized or already closed - " +
"call 'refresh' before accessing beans via the ApplicationContext");
}
return this.beanFactory;
}
}
3.prepareBeanFactory
BeanFactory的预准备工作
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// 1）、设置BeanFactory的类加载器
beanFactory.setBeanClassLoader(getClassLoader());
// 1）、设置支持表达式解析器
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// 2）、添加部分BeanPostProcessor【ApplicationContextAwareProcessor】
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
// 3）、设置忽略的自动装配的接口EnvironmentAware、EmbeddedValueResolverAware、xxx；
// 这些接口的实现类不能通过类型来自动注入
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// 4）、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下面方式直接注册使用
@autowired
BeanFactory beanFactory */
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// 5）、添加BeanPostProcessor【ApplicationListenerDetector】后置处理器，在bean初始化前后的一些工作
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// 6）、添加编译时的AspectJ；
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()));
}
// 7）、给BeanFactory中注册一些能用的组件；
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
// 环境信息ConfigurableEnvironment
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
//系统属性，systemProperties【Map<String, Object>】
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
//系统环境变量systemEnvironment【Map<String, Object>】
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
prepareBeanFactory方法就是为beanFactory做一些设置工作，传入一些后面会用到的参数和工具类，再在spring容器中创建一些bean；
4.postProcessBeanFactory
postProcessBeanFactory方法是留给子类扩展的，可以在bean实例初始化之前注册后置处理器（类似prepareBeanFactory方法中的beanFactory.addBeanPostProcessor），以子类AbstractRefreshableWebApplicationContext为例，其postProcessBeanFactory方法
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));
beanFactory.ignoreDependencyInterface(ServletContextAware.class);
beanFactory.ignoreDependencyInterface(ServletConfigAware.class);
WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);
WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
}
除了WebApplicationContextUtils类的工作之外，其余的都是和prepareBeanFactory方法中类似的处理
5.invokeBeanFactoryPostProcessors
nvokeBeanFactoryPostProcessors方法用来执行BeanFactory实例的后置处理器BeanFactoryPostProcessor的postProcessBeanFactory方法，这个后置处理器除了原生的，我们也可以自己扩展，用来对Bean的定义做一些修改，由于此时bean还没有实例化，所以不要在自己扩展的BeanFactoryPostProcessor中调用那些会触发bean实例化的方法（例如BeanFactory的getBeanNamesForType方法），源码的文档中有相关说明，不要触发bean的实例化，如果要处理bean实例请在BeanPostProcessor中进行；
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 (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
6.registerBeanPostProcessors
registerBeanPostProcessors方法的代码略多，就不在此贴出来了，简单的说，就是找出所有的bean的后置处理器(注意，是bean的后置处理器，不是beanFactory的后置处理器，bean后置处理器处理的是bean实例，beanfactory后置处理器处理的是bean的定义)，然后将这些bean的后置处理器分为三类：
- 实现了顺序接口Ordered.class的，先放入orderedPostProcessors集合，排序后顺序加入beanFactory的bean后处理集合中；
- 既没有实现Ordered.class，也没有实现PriorityOrdered.class的后置处理器，也加入到beanFactory的bean后处理集合中；
- 最后是实现了优先级接口PriorityOrdered.class的，排序后顺序加入beanFactory的bean后处理集合中；
registerBeanPostProcessors方法执行完毕后，beanFactory中已经保存了有序的bean后置处理器，在bean实例化之后，会依次使用这些后置处理器对bean实例来做对应的处理；
7.initMessageSource
initMessageSource方法用来准备国际化资源相关的，将实现了MessageSource接口的bean存放在ApplicationContext的成员变量中，先看是否有配置，如果有就实例化，否则就创建一个DelegatingMessageSource实例的bean
8.initApplicationEventMulticaster
spring中有事件、事件广播器、事件监听器等组成事件体系，在initApplicationEventMulticaster方法中对事件广播器做初始化，如果找不到此bean的配置，就创建一个SimpleApplicationEventMulticaster实例作为事件广播器的bean，并且保存为applicationContext的成员变量applicationEventMulticaster
/**
* Initialize the ApplicationEventMulticaster.
* Uses SimpleApplicationEventMulticaster if none defined in the context.
* @see org.springframework.context.event.SimpleApplicationEventMulticaster
*/
protected void initApplicationEventMulticaster() {
//获取BeanFactory
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 判断是否存在
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
// 从容器中获取ApplicationEventMulticaster对象
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isDebugEnabled()) {
logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
// 初始一个SimpleApplicationEventMulticaster对象
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
// 创建的对象注册到BeanFactory中
beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate ApplicationEventMulticaster with name '" +
APPLICATION_EVENT_MULTICASTER_BEAN_NAME +
"': using default [" + this.applicationEventMulticaster + "]");
}
}
}
9.onRefresh
onRefresh是个空方法，留给子类自己实现的，在实例化bean之前做一些ApplicationContext相关的操作，以子类AbstractRefreshableWebApplicationContext为例，看看它的onRefresh方法
/**
* Initialize the theme capability.
*/
@Override
protected void onRefresh() {
this.themeSource = UiApplicationContextUtils.initThemeSource(this);
}
10.registerListeners
方法名为registerListeners，看名字像是将监听器注册在事件广播器中，但实际情况并非如此，只有一些特殊的监听器被注册了，那些在bean配置文件中实现了ApplicationListener接口的类还没有实例化，所以此处只是将其name保存在广播器中，将这些监听器注册在广播器的操作是在bean的后置处理器中完成的，那时候bean已经实例化完成了，我们看代码
protected void registerListeners() {
// 注册的都是特殊的事件监听器，而并非配置中的bean
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!
// 根据接口类型找出所有监听器的名称
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
// 这里只是把监听器的名称保存在广播器中，并没有将这些监听器实例化！！！
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
}
11.finishBeanFactoryInitialization
finishBeanFactoryInitialization方法做了两件事：
- beanFactory对象的初始化；
- 我们在bean配置文件中配置的那些单例的bean，都是在finishBeanFactoryInitialization方法中实例化的；
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
// 实例化类型转换的bean，并保存在ApplicationContext中
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));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
// 实例化LoadTimeWeaverAware接口的bean，用于ApsectJ的类加载期织入的处理
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
// 确保临时的classLoader为空，临时classLoader一般被用来做类型匹配的
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
// 将一个标志设置为true，表示applicationContext已经缓存了所有bean的定义，这些bean的name都被保存在applicationContext的frozenBeanDefinitionNames成员变量中，相当于一个快照，记录了当前那些bean的定义已经拿到了
beanFactory.freezeConfiguration();
// 实例化所有还未实例化的单例bean
beanFactory.preInstantiateSingletons();
}
preInstantiateSingletons方法
public void preInstantiateSingletons() throws BeansException {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Pre-instantiating singletons in " + this);
}
// Iterate over a copy to allow for init methods which in turn register new bean definitions.
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
for (String beanName : beanNames) {
// 获取bean的定义，该定义已经和父类定义做了合并
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
// 非抽象类、是单例、非懒加载
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
//FactoryBean的处理
if (isFactoryBean(beanName)) {
final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
@Override
public Boolean run() {
return ((SmartFactoryBean<?>) factory).isEagerInit();
}
}, getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
else {
//非FactoryBean的实例化、初始化
getBean(beanName);
}
}
}
// Trigger post-initialization callback for all applicable beans...
// 单例实例化完成后，如果实现了SmartInitializingSingleton接口，afterSingletonsInstantiated就会被调用，此处用到了特权控制逻辑AccessController.doPrivileged
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
smartSingleton.afterSingletonsInstantiated();
return null;
}
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
doGetBean
protected <T> T doGetBean(
final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
throws BeansException {
final String beanName = transformedBeanName(name);
Object bean;
/**
2、先获取缓存中保存的单实例Bean。如果能获取到说明这个Bean之前被创建过（所有创建过的单实例Bean都会被缓存起来）
从private final Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(256);获取的
**/
Object sharedInstance = getSingleton(beanName);
//如果没有获取到创建bean
if (sharedInstance != null && args == null) {
if (logger.isDebugEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {//3、缓存中获取不到，开始Bean的创建对象流程；
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// 获取父beanFatory 检查这个bean是否创建了
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (args != null) {
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else {
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
}
// 4、标记当前bean已经被创建
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
try {
// 5、获取Bean的定义信息；
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// 6、【获取当前Bean依赖的其他Bean;如果有按照getBean()把依赖的Bean先创建出来；】
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
getBean(dep); //先创建依赖的bean
}
}
// 启动单实例的bean的创建流程
if (mbd.isSingleton()) {
//获取到单实例bean后，添加到缓存中 singletonObjects（）
//Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(256);
sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
try {
//创建Bean
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
destroySingleton(beanName);
throw ex;
}
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
// 下面部分不重要了
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
try {
return getTypeConverter().convertIfNecessary(bean, requiredType);
}
catch (TypeMismatchException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}
doCreateBean方法
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
throws BeanCreationException {
// bean的包装
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
// 1）、【创建Bean实例】利用工厂方法或者对象的构造器创建出Bean实例；
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
mbd.resolvedTargetType = beanType;
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
//调用MergedBeanDefinitionPostProcessor的postProcessMergedBeanDefinition(mbd, beanType, beanName);
//判断是否为：MergedBeanDefinitionPostProcessor 类型的，如果是，调用方法
//MergedBeanDefinitionPostProcessor 后置处理器是在bean实例换之后调用的
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
//判断bean 是否为单实例的，如果是单实例的添加到缓存中
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isDebugEnabled()) {
logger.debug("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
//添加bean到缓存中
addSingletonFactory(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
return getEarlyBeanReference(beanName, mbd, bean);
}
});
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
//为bean 赋值
populateBean(beanName, mbd, instanceWrapper);
if (exposedObject != null) {
// 4）、【Bean初始化】
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
}
else {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
}
}
if (earlySingletonExposure) {
//获取单实例bean,此时已经创建好了
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
if (exposedObject == bean) {
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
throw new BeanCurrentlyInCreationException(beanName,
"Bean with name '" + beanName + "' has been injected into other beans [" +
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
"] in its raw version as part of a circular reference, but has eventually been " +
"wrapped. This means that said other beans do not use the final version of the " +
"bean. This is often the result of over-eager type matching - consider using " +
"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// 5）、注册实现了DisposableBean 接口Bean的销毁方法；只是注册没有去执行，容器关闭之后才去调用的
try {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
populateBean()创建bean后属性赋值
//populateBean():1204, AbstractAutowireCapableBeanFactory
protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {
PropertyValues pvs = mbd.getPropertyValues();
if (bw == null) {
if (!pvs.isEmpty()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
return;
}
}
// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
// state of the bean before properties are set. This can be used, for example,
// to support styles of field injection.
boolean continueWithPropertyPopulation = true;
//赋值之前：
/* 1）、拿到InstantiationAwareBeanPostProcessor后置处理器；
执行处理器的postProcessAfterInstantiation()； 方法*/
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
//执行
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
if (!continueWithPropertyPopulation) {
return;
}
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// autowire 按name注入
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// autowire 按类型注入
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
/*2）、拿到InstantiationAwareBeanPostProcessor后置处理器；
执行 postProcessPropertyValues()； 获取到属性的值，此时还未赋值*/
if (hasInstAwareBpps || needsDepCheck) {
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
if (hasInstAwareBpps) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvs == null) {
return;
}
}
}
}
if (needsDepCheck) {
checkDependencies(beanName, mbd, filteredPds, pvs);
}
}
//=====赋值之前：===
//3）、应用Bean属性的值；为属性利用setter方法等进行赋值；
applyPropertyValues(beanName, mbd, bw, pvs);
}
Bean初始化 initializeBean
//初始化
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
invokeAwareMethods(beanName, bean);
return null;
}
}, getAccessControlContext());
}
else {
//1）、【执行Aware接口方法】invokeAwareMethods(beanName, bean);执行xxxAware接口的方法
//判断是否实现了 BeanNameAware\BeanClassLoaderAware\BeanFactoryAware 这些接口的bean，如果是执行相应的方法
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
//2）、【执行后置处理器BeanPostProcessor初始化之前】 执行所有的 BeanPostProcessor.postProcessBeforeInitialization（）;
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
//3）、【执行初始化方法】
invokeInitMethods(beanName, wrappedBean, mbd);
}
catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),
beanName, "Invocation of init method failed", ex);
}
//4）、【执行后置处理器初始化之后】 执行所有的beanProcessor.postProcessAfterInitialization(result, beanName);方法
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
执行bean的初始化方法init
1）是否是InitializingBean接口的实现；执行接口规定的初始化；
2）是否自定义初始化方法；通过注解的方式添加了initMethod方法的，
例如： @Bean(initMethod="init",destroyMethod="detory")
//invokeInitMethods():1667, AbstractAutowireCapableBeanFactory
protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
throws Throwable {
//1）、是否是InitializingBean接口的实现；执行接口规定的初始化 ,执行afterPropertiesSet()这个方法；
boolean isInitializingBean = (bean instanceof InitializingBean);
if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
if (logger.isDebugEnabled()) {
logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
}
if (System.getSecurityManager() != null) {
try {
AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
@Override
public Object run() throws Exception {
((InitializingBean) bean).afterPropertiesSet();
return null;
}
}, getAccessControlContext());
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
//执行实现InitializingBean的afterPropertiesSet方法
((InitializingBean) bean).afterPropertiesSet();
}
}
if (mbd != null) {
//执行通过注解自定义的initMethod 方法
String initMethodName = mbd.getInitMethodName();
if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}
12.finishRefresh
最后一个方法是finishRefresh，这是在bean的实例化、初始化等完成后的一些操作，例如生命周期变更的回调，发送applicationContext刷新完成的广播等，展开看看
protected void finishRefresh() {
// 检查是否已经配置了生命周期处理器，如果没有就new一个DefaultLifecycleProcessor
initLifecycleProcessor();
// 找到所有实现了Lifecycle接口的bean，按照每个bean设置的生命周期阶段进行分组，再依次调用每个分组中每个bean的start方法，完成生命周期监听的通知
getLifecycleProcessor().onRefresh();
// 创建一条代表applicationContext刷新完成的事件，交给广播器去广播
publishEvent(new ContextRefreshedEvent(this));
// 如果配置了MBeanServer，就完成在MBeanServer上的注册
LiveBeansView.registerApplicationContext(this);
}
Spring启动流程总结
- Spring容器在启动的时候，先会保存所有注册进来的Bean的定义信息；
1.1 xml注册bean；
1.2 注解注册Bean；@Service、@Component、@Bean、xxx - Spring容器会合适的时机创建这些Bean
2.1用到这个bean的时候；利用getBean创建bean；创建好以后保存在容器中；
2.2统一创建剩下所有的bean的时候；finishBeanFactoryInitialization()； - 后置处理器；BeanPostProcessor
每一个bean创建完成，都会使用各种后置处理器进行处理；来增强bean的功能；
AutowiredAnnotationBeanPostProcessor:处理自动注入
AnnotationAwareAspectJAutoProxyCreator:来做AOP功能； - 事件驱动模型；
ApplicationListener；事件监听；
ApplicationEventMulticaster；事件派发：