public interface InitializingBean {

     /**

      * 该方法在BeanFactory设置完了所有的属性之后被调用<br/>

      * 该方法允许bean实例设置了所有bean属性时执行初始化工作，如果该过程出现了错误，则需要抛出异常<br/>

      * Invoked by the containing {@code BeanFactory} after it has set all bean properties

      * and satisfied {@link BeanFactoryAware}, {@code ApplicationContextAware} etc.

      * <p>This method allows the bean instance to perform validation of its overall

      * configuration and final initialization when all bean properties have been set.

      *

      * @throws Exception in the event of misconfiguration (such as failure to set an

      *                   essential property) or if initialization fails for any other reason

      */

     void afterPropertiesSet() throws Exception;

 }

 public class UserDefinedInitializingBean implements InitializingBean {

     private String msg;

     public String getMsg() {

         return msg;

     }

     public void setMsg(String msg) {

         this.msg = msg;

     }

     @Override

     public void afterPropertiesSet() throws Exception {

         System.out.println("InitializingBean afterPropertiesSet......");

         this.msg = "修改了msg，msg=hello initializingBean！！！！！！";

     }

 }

 <bean id="userDefinedInitializingBean" class="com.dev.basebean.initializingbean.UserDefinedInitializingBean"

           p:msg="i am msg!!!"/>

 @Test

     public void initializingBeanTest() {

         ApplicationContext context = new ClassPathXmlApplicationContext("classpath*:com/dev/config/initializingbean/initializingbean.xml");

         UserDefinedInitializingBean initializingBean = context.getBean(UserDefinedInitializingBean.class);

         System.out.println(initializingBean.getMsg());

     }

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

             throws Throwable {

         // 首先先检查是否是InitializingBean，如果是，则需要调用afterPropertiesSet()

         boolean isInitializingBean = (bean instanceof InitializingBean);

         if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {

             if (logger.isDebugEnabled()) {

                 logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");

             }

             // 安全模式

             if (System.getSecurityManager() != null) {

                 try {

                     AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {

                         ((InitializingBean) bean).afterPropertiesSet();

                         return null;

                     }, getAccessControlContext());

                 } catch (PrivilegedActionException pae) {

                     throw pae.getException();

                 }

             } else {

                 // 属性初始化处理

                 ((InitializingBean) bean).afterPropertiesSet();

             }

         }

         if (mbd != null && bean.getClass() != NullBean.class) {

             String initMethodName = mbd.getInitMethodName();

             if (StringUtils.hasLength(initMethodName) &&

                     !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&

                     !mbd.isExternallyManagedInitMethod(initMethodName)) {

                 // 激活用户自定义的初始化方法

                 invokeCustomInitMethod(beanName, bean, mbd);

             }

         }

     }

 <bean id="userDefinedInitializingBean" class="com.dev.basebean.initializingbean.UserDefinedInitializingBean"

           p:msg="i am msg!!!" init-method="initMethod"/>

 public void initMethod() {

         System.out.println("通过init-method方法对msg属性进行修改");

         this.msg = "修改了msg，msg=hello init-method!!!!!!";

     }