/** 
   * Initialize the root web application context. 
   */ 
  @Override 
  public void contextInitialized(ServletContextEvent event) { 
    initWebApplicationContext(event.getServletContext()); 
  } 

if (this.context == null) { 
  this.context = createWebApplicationContext(servletContext); 
} 
if (this.context instanceof ConfigurableWebApplicationContext) { 
  ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context; 
  if (!cwac.isActive()) { 
    // The context has not yet been refreshed -> provide services such as 
    // setting the parent context, setting the application context id, etc 
    if (cwac.getParent() == null) { 
      // The context instance was injected without an explicit parent -> 
      // determine parent for root web application context, if any. 
      ApplicationContext parent = loadParentContext(servletContext); 
      cwac.setParent(parent); 
    } 
    configureAndRefreshWebApplicationContext(cwac, servletContext); 
  } 
} 

import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Service;
@Service
public class StartupListenerimplements
 ApplicationListener<ContextRefreshedEvent>
{
  @Override
  public void onApplicationEvent(ContextRefreshedEvent event)
  {
    if(event.getApplicationContext().getParent() == null)//root application context 没有parent，他就是老大.
    { 
      //需要执行的逻辑代码，当spring容器初始化完成后就会执行该方法。 
      System.out.println("\n\n\n\n\n______________\n\n\n加载了\n\n_________\n\n");
    } 
    
    //或者下面这种方式
    if(event.getApplicationContext().getDisplayName().equals("Root WebApplicationContext"))
    {
      System.out.println("\n\n\n_________\n\n加载一次的 \n\n ________\n\n\n\n");
    }
    
  }
}

<!-- 注册@Controller 、@Service-->
  <context:component-scan base-package="com.test.controller" use-default-filters="false">
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller" />
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Service" />
  </context:component-scan>

@Override 
   public void onApplicationEvent(ContextRefreshedEvent event) { 
    if(event.getApplicationContext().getParent() == null){//root application context 没有parent，他就是老大. 
       //需要执行的逻辑代码，当spring容器初始化完成后就会执行该方法。 
    } 
   }