/**
* 初始化所有非懒加载的单例bean
*/
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// 1.初始化此上下文的转换服务
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));
}
// 2.如果beanFactory之前没有注册嵌入值解析器,则注册默认的嵌入值解析器:主要用于注解属性值的解析。
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// 3.初始化所有LoadTimeWeaverAware Bean实例对象
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// 4.冻结所有bean定义,注册的bean定义不会被修改或进一步后处理,因为马上要创建 Bean 实例对象了
beanFactory.freezeConfiguration();
// 5.实例化所有剩余(非懒加载)单例对象
beanFactory.preInstantiateSingletons();
}
这里看一下beanFactory.preInstantiateSingletons()方法
/**
* 初始化非懒加载的单例bean
*/
@Override
public void preInstantiateSingletons() throws BeansException {
if (logger.isTraceEnabled()) {
logger.trace("Pre-instantiating singletons in " + this);
}
// 1.创建beanDefinitionNames的副本beanNames用于后续的遍历,以允许init等方法注册新的bean定义
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// 遍历beanNames,触发所有非懒加载单例bean的初始化
for (String beanName : beanNames) {
//3.获取beanName对应的MergedBeanDefinition
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
// 4.bd对应的Bean实例:不是抽象类 && 是单例 && 不是懒加载
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
// 5.判断beanName对应的bean是否为FactoryBean
if (isFactoryBean(beanName)) {
// 5.1 通过beanName获取FactoryBean实例
// 通过getBean(&beanName)拿到的是FactoryBean本身;通过getBean(beanName)拿到的是FactoryBean创建的Bean实例
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) { //判断bean是否实现了FactoryBean
final FactoryBean<?> factory = (FactoryBean<?>) bean;
// 5.2 判断这个FactoryBean是否希望急切的初始化
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
// 5.3 如果希望急切的初始化,则通过beanName获取bean实例
getBean(beanName);
}
}
}
else {
// 6.如果beanName对应的bean不是FactoryBean,只是普通Bean,通过beanName获取bean实例
getBean(beanName);
}
}
}
// 7.遍历beanNames,触发所有SmartInitializingSingleton的后初始化回调
for (String beanName : beanNames) {
// 7.1 拿到beanName对应的bean实例
Object singletonInstance = getSingleton(beanName);
// 7.2 判断singletonInstance是否实现了SmartInitializingSingleton接口
if (singletonInstance instanceof SmartInitializingSingleton) {
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
// 7.3 触发SmartInitializingSingleton实现类的afterSingletonsInstantiated方法
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
获取beanName对应的MergedBeanDefinition
/**
* 根据beanName获取RootBeanDefinition
*/
protected RootBeanDefinition getMergedLocalBeanDefinition(String beanName) throws BeansException {
//1.检查beanName对应的MergedBeanDefinition是否存在于缓存中
RootBeanDefinition mbd = this.mergedBeanDefinitions.get(beanName);
if (mbd != null && !mbd.stale) {
return mbd;//2.如果存在于缓存中则直接返回
}
/*3.如果不存在于缓存中
* 3.1 getBeanDefinition(beanName): 获取beanName对应的BeanDefinition,从beanDefinitionMap缓存中获取
* 3.2 getMergedBeanDefinition: 根据beanName和对应的BeanDefinition,获取MergedBeanDefinition
*/
return getMergedBeanDefinition(beanName, getBeanDefinition(beanName));
}
/**
* 获取beanName对应的BeanDefinition,从beanDefinitionMap缓存中获取
*/
@Override
public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
BeanDefinition bd = this.beanDefinitionMap.get(beanName); //从beanDefinitionMap中获取
if (bd == null) {
if (logger.isTraceEnabled()) {
logger.trace("No bean named '" + beanName + "' found in " + this);
}
throw new NoSuchBeanDefinitionException(beanName); //未获取到,直接抛出异常
}
return bd; //返回结果
}
/**
* 根据beanName和对应的BeanDefinition,获取MergedBeanDefinition
*/
protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd)
throws BeanDefinitionStoreException {
return getMergedBeanDefinition(beanName, bd, null);
}
/**
* 根据beanName和对应的BeanDefinition,获取MergedBeanDefinition
*/
protected RootBeanDefinition getMergedBeanDefinition(
String beanName, BeanDefinition bd, @Nullable BeanDefinition containingBd)
throws BeanDefinitionStoreException {
//1.加锁再进行操作
synchronized (this.mergedBeanDefinitions) {
//用于存储bd的MergedBeanDefinition,也就是该方法的结果
RootBeanDefinition mbd = null;
RootBeanDefinition previous = null;
if (containingBd == null) {
//2.检查beanName对应的MergedBeanDefinition是否存在于缓存中
//从mergedBeanDefinitions中获取
mbd = this.mergedBeanDefinitions.get(beanName);
}
// 3.如果beanName对应的MergedBeanDefinition不存在于缓存中
if (mbd == null || mbd.stale) {
previous = mbd;
mbd = null;
//4.如果bd的parentName为空,代表bd没有父定义,无需与父定义进行合并操作,也就是bd的MergedBeanDefinition就是bd本身(可能需要转成RootBeanDefinition)
if (bd.getParentName() == null) {
// Use copy of given root bean definition.
if (bd instanceof RootBeanDefinition) {
// 4.1 如果bd的类型为RootBeanDefinition,则bd的MergedBeanDefinition就是bd本身,则直接克隆一个副本
mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();
}
else {
// 4.2 否则,将bd作为参数,构建一个RootBeanDefinition。
// 正常使用下,BeanDefinition在被加载后是GenericBeanDefinition或ScannedGenericBeanDefinition
mbd = new RootBeanDefinition(bd);
}
}
else {
// 5.否则,bd存在父定义,需要与父定义合并
BeanDefinition pbd;
try {
// 5.1 获取父定义的beanName
String parentBeanName = transformedBeanName(bd.getParentName());
// 5.2 如果父定义的beanName与该bean的beanName不同
if (!beanName.equals(parentBeanName)) {
// 5.3 获取父定义的MergedBeanDefinition(因为父定义也可能有父定义,也就是bd的爷爷定义...)
pbd = getMergedBeanDefinition(parentBeanName);
}
else {
// 5.4 如果父定义的beanName与bd的beanName相同,则拿到父BeanFactory,
// 只有在存在父BeanFactory的情况下,才允许父定义beanName与自己相同,否则就是将自己设置为父定义
BeanFactory parent = getParentBeanFactory();
if (parent instanceof ConfigurableBeanFactory) {
// 5.5 如果父BeanFactory是ConfigurableBeanFactory,则通过父BeanFactory获取父定义的MergedBeanDefinition
pbd = ((ConfigurableBeanFactory) parent).getMergedBeanDefinition(parentBeanName);
}
else {
// 5.6 如果父BeanFactory不是ConfigurableBeanFactory,则抛异常
throw new NoSuchBeanDefinitionException(parentBeanName,
"Parent name '" + parentBeanName + "' is equal to bean name '" + beanName +
"': cannot be resolved without an AbstractBeanFactory parent");
}
}
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanName,
"Could not resolve parent bean definition '" + bd.getParentName() + "'", ex);
}
// 5.7 使用父定义pbd构建一个新的RootBeanDefinition对象(深拷贝)
mbd = new RootBeanDefinition(pbd);
// 5.8 使用bd覆盖父定义
mbd.overrideFrom(bd);
}
// 6.如果没有配置scope,则设置成默认的singleton
if (!StringUtils.hasLength(mbd.getScope())) {
mbd.setScope(RootBeanDefinition.SCOPE_SINGLETON);
}
// 7.如果containingBd不为空 && containingBd不为singleton && mbd为singleton,则将mdb的scope设置为containingBd的scope
if (containingBd != null && !containingBd.isSingleton() && mbd.isSingleton()) {
mbd.setScope(containingBd.getScope());
}
// 8.将beanName与mbd放到mergedBeanDefinitions缓存,以便之后可以直接使用
if (containingBd == null && isCacheBeanMetadata()) {
this.mergedBeanDefinitions.put(beanName, mbd);
}
}
if (previous != null) { //即mbd != null && mbd.stale为true
copyRelevantMergedBeanDefinitionCaches(previous, mbd); //copyRelevantMergedBeanDefinitionCaches处理mbd
}
// 9.返回MergedBeanDefinition
return mbd;
}
}
初始化bean时,会校验 不是抽象类 && 是单例 && 不是懒加载,若bean是FactoryBean,会先获取FactoryBean实例,然后根据需求初始化FactoryBean对应的bean实例,isFactoryBean判断方法
/**
*判断beanName对应的bean是否为FactoryBean
*/
@Override
public boolean isFactoryBean(String name) throws NoSuchBeanDefinitionException {
// 1.拿到真正的beanName(去掉&前缀、解析别名)
String beanName = transformedBeanName(name);
// 2.尝试从缓存获取Bean实例对象
Object beanInstance = getSingleton(beanName, false); //获取实例
if (beanInstance != null) {
// 3.beanInstance存在,则直接判断类型是否为FactoryBean
return (beanInstance instanceof FactoryBean); //是否实现了FactoryBean接口
}
// 4.如果beanInstance为null,并且beanName在单例对象缓存中,则代表beanName对应的单例对象为空对象,返回false
// 5.如果缓存中不存在此beanName && 父beanFactory是ConfigurableBeanFactory,则调用父BeanFactory判断是否为FactoryBean
if (!containsBeanDefinition(beanName) && getParentBeanFactory() instanceof ConfigurableBeanFactory) {
// No bean definition found in this factory -> delegate to parent.
return ((ConfigurableBeanFactory) getParentBeanFactory()).isFactoryBean(name);
}
// 6.通过MergedBeanDefinition来检查beanName对应的Bean是否为FactoryBean
return isFactoryBean(beanName, getMergedLocalBeanDefinition(beanName));
}
getSingleton
/**
* 获取一个单例bean
* allowEarlyReference 是否进行创建早期单例对象
*/
@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
//1.从单例对象缓存中获取beanName对应的单例对象
Object singletonObject = this.singletonObjects.get(beanName);
// 2.如果单例对象缓存中没有,并且该beanName对应的单例bean正在创建中
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
// 3.加锁进行操作
synchronized (this.singletonObjects) {
// 4.从早期单例对象缓存中获取单例对象(之所称成为早期单例对象,是因为earlySingletonObjects里
// 的对象的都是通过提前曝光的ObjectFactory创建出来的,还未进行属性填充等操作)
singletonObject = this.earlySingletonObjects.get(beanName);
// 5.如果在早期单例对象缓存中也没有,并且允许创建早期单例对象引用
if (singletonObject == null && allowEarlyReference) {
// 6.从单例工厂缓存中获取beanName的单例工厂
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
// 7.如果存在单例对象工厂,则通过工厂创建一个单例对象
singletonObject = singletonFactory.getObject();
// 8.将通过单例对象工厂创建的单例对象,放到早期单例对象缓存中
this.earlySingletonObjects.put(beanName, singletonObject);
// 9.移除该beanName对应的单例对象工厂,因为该单例工厂已经创建了一个实例对象,并且放到earlySingletonObjects缓存了,
// 因此,后续获取beanName的单例对象,可以通过earlySingletonObjects缓存拿到,不需要在用到该单例工厂
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject; //返回对象
}
/**
* 判断对象是否正在创建
*/
public boolean isSingletonCurrentlyInCreation(String beanName) {
return this.singletonsCurrentlyInCreation.contains(beanName);
}
isFactoryBean(beanName, getMergedLocalBeanDefinition(beanName))
/**
* 通过RootBeanDefinition检查bean是否为FactoryBean
*/
protected boolean isFactoryBean(String beanName, RootBeanDefinition mbd) {
Boolean result = mbd.isFactoryBean;
if (result == null) {
Class<?> beanType = predictBeanType(beanName, mbd, FactoryBean.class); //获取bean的class
result = (beanType != null && FactoryBean.class.isAssignableFrom(beanType)); //判断beanType是否为FactoryBean的子类
mbd.isFactoryBean = result;
}
return result;
}
最后就是getBean初始化bean的方法。。。