SpringBean实例化对象

1. Spring Bean实例化

1. 通过BeanName获取Class对象（resolveBeanClass(mbd, beanName);）

2. 处理lookup标签（mbdToUse.prepareMethodOverrides();）// Prepare method overrides.

3. 短路Bean的创建过程 Object bean = resolveBeforeInstantiation(beanName, mbdToUse);

// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.

Object bean = resolveBeforeInstantiation(beanName, mbdToUse);

if (bean != null) {

    return bean;

}

 

Class<?> targetType = determineTargetType(beanName, mbd);

if (targetType != null) {

    bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);

    if (bean != null) {

        bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);

    }

}

    

protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {

    for (BeanPostProcessor bp : getBeanPostProcessors()) {

        if (bp instanceof InstantiationAwareBeanPostProcessor) {

            InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;

            Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);

            if (result != null) {

                return result;

            }

        }

    }

    return null;

}

 

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)

        throws BeansException {

 

    Object result = existingBean;

    for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {

        result = beanProcessor.postProcessAfterInitialization(result, beanName);

        if (result == null) {

            return result;

        }

    }

    return result;

}

4. 实例化对象（doCreateBean(beanName, mbdToUse, args);）

• 实例化对象（instanceWrapper = createBeanInstance(beanName, mbd, args)）
• 使用FactoryMethod实例化（instantiateUsingFactoryMethod(beanName, mbd, args);）
• 解析过构造参数或FactoryMethod，才使用构造参数实例化（autowireConstructor(beanName, mbd, null, null);）
• 使用策略实例化（instantiateBean(beanName, mbd);）InstantiationStrategy instantiationStrategy = new CglibSubclassingInstantiationStrategy();
• if (bd.getMethodOverrides().isEmpty()) {
•     // 反射初始化
•     return BeanUtils.instantiateClass(constructorToUse);
• } else {
•     // Must generate CGLIB subclass.
•     return instantiateWithMethodInjection(bd, beanName, owner);
• }
•  
• 提前曝光实例（addSingletonFactory），循环依赖使用
• 填充属性（populateBean(beanName, mbd, instanceWrapper);）
• 短路属性注入 bp instanceof InstantiationAwareBeanPostProcessor / !ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)if (bp instanceof InstantiationAwareBeanPostProcessor) {
•     InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
•     if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
•         continueWithPropertyPopulation = false;
•         break;
•     }
• }
•  
• 属性注入，按照名称（autowireByName(beanName, mbd, bw, newPvs);）或类型（autowireByType(beanName, mbd, bw, newPvs);）注入
• 短路if (bp instanceof InstantiationAwareBeanPostProcessor) {
•             InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
•             pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
•             if (pvs == null) {
•                 return;
•             }
• }
•  
• 应用属性（applyPropertyValues(beanName, mbd, bw, pvs);Spel表达式解析）
• 初始化Bean（initializeBean(beanName, exposedObject, mbd);）
• 执行Aware接口自动注入，包括BeanNameAware、BeanFactoryAware、BeanClassLoaderAware（invokeAwareMethods(beanName, bean);）
• 短路bean后续BeanPostProcessor执行。postProcessBeforeInitializationresult = beanProcessor.postProcessBeforeInitialization(result, beanName);
• if (result == null) {
•     return result;
• }
•  
• 执行init初始化方法（invokeInitMethods(beanName, wrappedBean, mbd);）
• ((InitializingBean) bean).afterPropertiesSet();
• invokeCustomInitMethod(beanName, bean, mbd);
• 短路bean后续BeanPostProcessor执行。wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
•     result = beanProcessor.postProcessAfterInitialization(result, beanName);
•     if (result == null) {
•         return result;
•     }
• }
•  

5. 初始化依赖的Bean

6. Register bean as disposable.（registerDisposableBeanIfNecessary(beanName, bean, mbd);）