當spring完成屬性註入之後, 就要開始 bean 的初始化了

代碼片段:

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean

// Initialize the bean instance.
Object exposedObject = bean;
try {
    //設置屬性，非常重要
    populateBean(beanName, mbd, instanceWrapper);
    //執行後置處理器，一部分aop就是在這裡完成的處理
    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);
    }
}

進去看裡面的內容:

protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
    if (System.getSecurityManager() != null) {
        AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
            invokeAwareMethods(beanName, bean);
            return null;
        }, getAccessControlContext());
    }
    else {
        //調用 BeanNameAware BeanClassLoaderAware BeanFactoryAware 定義的方法
        invokeAwareMethods(beanName, bean);
    }

    Object wrappedBean = bean;
    if (mbd == null || !mbd.isSynthetic()) {
        //初始化之前, 執行後置處理的 before方法
        wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
    }

    try {
        //執行bean的聲明周期回調中的init方法
        invokeInitMethods(beanName, wrappedBean, mbd);
    }
    catch (Throwable ex) {
        throw new BeanCreationException(
                (mbd != null ? mbd.getResourceDescription() : null),
                beanName, "Invocation of init method failed", ex);
    }
    if (mbd == null || !mbd.isSynthetic()) {
        //初始化之後, 執行後置處理器的 after方法
        wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
    }

    return wrappedBean;
}

這裡在初始化之前和初始化之後, 都調用了 Bean 的後置處理器響應的處理方法.

invokeAwareMethods

這個方法, 主要是處理幾個 Aware 的. 分別調用他們定義的介面方法, 實現一些屬性的註入工作

private void invokeAwareMethods(final String beanName, final Object bean) {
    if (bean instanceof Aware) {
        if (bean instanceof BeanNameAware) {
            ((BeanNameAware) bean).setBeanName(beanName);
        }
        if (bean instanceof BeanClassLoaderAware) {
            ClassLoader bcl = getBeanClassLoader();
            if (bcl != null) {
                ((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
            }
        }
        if (bean instanceof BeanFactoryAware) {
            ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
        }
    }
}

applyBeanPostProcessorsBeforeInitialization

初始化之前的後置處理

 https://www.cnblogs.com/elvinle/p/13385304.html

invokeInitMethods

protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd)
        throws Throwable {

    boolean isInitializingBean = (bean instanceof InitializingBean);
    //這裡主要處理實現了 InitializingBean 介面的類, 調用其 afterPropertiesSet(), 進行初始化工作
    if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
        if (logger.isTraceEnabled()) {
            logger.trace("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
        }
        if (System.getSecurityManager() != null) {
            try {
                AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
                    ((InitializingBean) bean).afterPropertiesSet();
                    return null;
                }, getAccessControlContext());
            }
            catch (PrivilegedActionException pae) {
                throw pae.getException();
            }
        }
        else {
            ((InitializingBean) bean).afterPropertiesSet();
        }
    }

    //調用用戶自定義的初始化方法, 如 xml 中配置的 init-method 方法
    if (mbd != null && bean.getClass() != NullBean.class) {
        String initMethodName = mbd.getInitMethodName();
        if (StringUtils.hasLength(initMethodName) &&
                !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
                !mbd.isExternallyManagedInitMethod(initMethodName)) {
            invokeCustomInitMethod(beanName, bean, mbd);
        }
    }
}

applyBeanPostProcessorsAfterInitialization

初始化之後的後置處理

 https://www.cnblogs.com/elvinle/p/13385317.html