JSP 开发之servlet中调用注入spring管理的dao

private UserDao userDao; 
   
    public void init() throws ServletException { 
    super.init(); 
     
    ServletContext servletContext = this.getServletContext(); 
     
    WebApplicationContext ctx = WebApplicationContextUtils.getWebApplicationContext(servletContext); 
     
    userDao = (UserDao)ctx.getBean("userDao"); 
  } 

public UserDao getUserDao() { 
    return userDao; 
  } 
 
  public void setUserDao(UserDao userDao) { 
    this.userDao = userDao; 
  }