Spring学习笔记-在Filter中获取SpingIOC容器

在spring项目中，有时需要在filter中操作数据库，由于整个项目有spring容器进行管理，所有不能直接利用new来创建对象，需要从spring容器中获取所需对象，但是直接利用注解进行注入是行不通的，因为在整个项目架构中，Filter与Spring容器是解耦合的，那么怎么办的，看下面的代码示例：

public class ValidateFilter implements Filter{


    private UserService userService;

    private static WebApplicationContext ac;

    @Override
    public void destroy() {}
    @Override
    public void init(FilterConfig config) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
            throws IOException, ServletException {
         HttpServletRequest request = (HttpServletRequest)req;
         HttpServletResponse response = (HttpServletResponse)resp;

         if(ac == null){
             //获取Spring容器上下文
             ac = WebApplicationContextUtils.getRequiredWebApplicationContext(request.getServletContext());
         }
         //从
         userService = (UserService)ac.getBean("UserServiceImpl");
         String config  = userService.getValidateConfig();

         //如果标记为 1，则不进行密码验证过滤。
         if("1".equals(config)){
             chain.doFilter(request, response);
         }else if("2".equals(config)){
                 HttpSession session = request.getSession();

                 String validateFlag = (String)session.getAttribute("validateFlag");
                 if(validateFlag != null && "true".equals(validateFlag)){
                      chain.doFilter(request, response);
                 }else{
                     String password = request.getParameter("password");
                     if(password != null && "Garden9".equals(password)){
                         session.setAttribute("validateFlag", "true");
                         chain.doFilter(request, response);
                     }else{
                         request.getRequestDispatcher("/jsp/password_validate.jsp").forward(request, response);
                     }
                 }
         }
    }
}