摘要：一接口說明接口為提供了屬性初始化后的處理方法，它只包括方法，凡是繼承該接口的類，在的屬性初始化后都會執(zhí)行該方法。三接口應(yīng)用接口在框架中本身就很多應(yīng)用，這就不多說了。

一、InitializingBean接口說明
InitializingBean接口為bean提供了屬性初始化后的處理方法，它只包括afterPropertiesSet方法，凡是繼承該接口的類，在bean的屬性初始化后都會執(zhí)行該方法。

package org.springframework.beans.factory;

/**
 * Interface to be implemented by beans that need to react once all their
 * properties have been set by a BeanFactory: for example, to perform custom
 * initialization, or merely to check that all mandatory properties have been set.
 *
 * 
An alternative to implementing InitializingBean is specifying a custom
 * init-method, for example in an XML bean definition.
 * For a list of all bean lifecycle methods, see the BeanFactory javadocs.
 *
 * @author Rod Johnson
 * @see BeanNameAware
 * @see BeanFactoryAware
 * @see BeanFactory
 * @see org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName
 * @see org.springframework.context.ApplicationContextAware
 */
public interface InitializingBean {

    /**
     * Invoked by a BeanFactory after it has set all bean properties supplied
     * (and satisfied BeanFactoryAware and ApplicationContextAware).
     * 
This method allows the bean instance to perform initialization only
     * possible when all bean properties have been set and to throw an
     * exception in the event of misconfiguration.
     * @throws Exception in the event of misconfiguration (such
     * as failure to set an essential property) or if initialization fails.
     */
    void afterPropertiesSet() throws Exception;

}

從方法名afterPropertiesSet也可以清楚的理解該方法是在屬性設(shè)置后才調(diào)用的。
二、源碼分析接口應(yīng)用
通過查看spring的加載bean的源碼類(AbstractAutowireCapableBeanFactory)可以看到

protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
            throws Throwable {
//判斷該bean是否實現(xiàn)了實現(xiàn)了InitializingBean接口，如果實現(xiàn)了InitializingBean接口，則調(diào)用bean的afterPropertiesSet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