如何手动获取Spring容器中的bean（ApplicationContextAware 接口）

public class SpringContextUtils implements ApplicationContextAware {
    private static ApplicationContext context;
    @Override
    public void setApplicationContext(ApplicationContext context)
            throws BeansException {
        SpringContextUtils.context = context;
    }
    public static ApplicationContext getContext(){
        return context;
    }
}

<!--Spring中bean获取的工具类-->
<bean id="springContextUtils" class="com.zker.common.util.SpringContextUtils" />

    /**
     * 利用Ajax实现注册的用户名重复性校验
     * @return
     */
    public String ajaxRegister() throws IOException {
        UserDao userDao = (UserDao)SpringContextUtils.getContext().getBean("userDao");
        if (userDao.findAdminByLoginName(loginName) != null
                || userDao.findUserByLoginName(loginName) != null) {
            message.setMsg("用户名已存在");
            message.setStatus(false);
        } else {
            message.setMsg("用户名可以注册");
            message.setStatus(true);
        }
        return "register";
    }