AbstractBeanFactory 生产Bean 实例对象

AbstractBeanFactory 类中生产Bean 实例对象的主要源码如下：

//Bean工厂生产Bean实例对象
protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {//Bean工厂是单态模式，并且Bean工厂缓存中存在指定名称的Bean实例对象if (factory.isSingleton() && containsSingleton(beanName)) {//多线程同步，以防止数据不一致synchronized (getSingletonMutex()) {//直接从Bean工厂缓存中获取指定名称的Bean实例对象Object object = this.factoryBeanObjectCache.get(beanName);//Bean工厂缓存中没有指定名称的实例对象，则生产该实例对象if (object == null) {//调用Bean工厂的getObject方法生产指定Bean的实例对象object = doGetObjectFromFactoryBean(factory, beanName);// Only post-process and store if not put there already during getObject() call above// (e.g. because of circular reference processing triggered by custom getBean calls)Object alreadyThere = this.factoryBeanObjectCache.get(beanName);if (alreadyThere != null) {object = alreadyThere;}else {if (shouldPostProcess) {try {object = postProcessObjectFromFactoryBean(object, beanName);}catch (Throwable ex) {throw new BeanCreationException(beanName,"Post-processing of FactoryBean's singleton object failed", ex);}}//将生产的实例对象添加到Bean工厂缓存中this.factoryBeanObjectCache.put(beanName, object);}}return object;}}//调用Bean工厂的getObject方法生产指定Bean的实例对象else {Object object = doGetObjectFromFactoryBean(factory, beanName);if (shouldPostProcess) {try {object = postProcessObjectFromFactoryBean(object, beanName);}catch (Throwable ex) {throw new BeanCreationException(beanName, "Post-processing of FactoryBean's object failed", ex);}}return object;}
}

//调用Bean工厂的getObject方法生产指定Bean的实例对象
private Object doGetObjectFromFactoryBean(final FactoryBean<?> factory, final String beanName)throws BeanCreationException {Object object;try {if (System.getSecurityManager() != null) {AccessControlContext acc = getAccessControlContext();try {//实现PrivilegedExceptionAction接口的匿名内置类//根据JVM检查权限，然后决定BeanFactory创建实例对象object = AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () ->factory.getObject(), acc);}catch (PrivilegedActionException pae) {throw pae.getException();}}else {//调用BeanFactory接口实现类的创建对象方法object = factory.getObject();}}catch (FactoryBeanNotInitializedException ex) {throw new BeanCurrentlyInCreationException(beanName, ex.toString());}catch (Throwable ex) {throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);}// Do not accept a null value for a FactoryBean that's not fully// initialized yet: Many FactoryBeans just return null then.//创建出来的实例对象为null，或者因为单态对象正在创建而返回nullif (object == null) {if (isSingletonCurrentlyInCreation(beanName)) {throw new BeanCurrentlyInCreationException(beanName, "FactoryBean which is currently in creation returned null from getObject");}object = new NullBean();}return object;
}

从上面的源码分析中，我们可以看出，BeanFactory 接口调用其实现类的getObject 方法来实现创建Bean 实例对象的功能。

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AbstractBeanFactory 生产Bean 实例对象

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