拦截器概述

一，未登陆拦截器

1，创建LoginInterceptor

public class LoginInterceptor implements HandlerInterceptor {
    
    @Override
    public void afterCompletion(HttpServletRequest req,
            HttpServletResponse resp, Object obj, Exception ex)
            throws Exception {
        System.out.println("============afterCompletion");
    }
    
    @Override
    public void postHandle(HttpServletRequest req, HttpServletResponse resp,
            Object obj, ModelAndView mav) throws Exception {
        System.out.println("============postHandle");
    }
    
    @Override
    public boolean preHandle(HttpServletRequest req, HttpServletResponse resp,
            Object obj) throws Exception {
        System.out.println("============preHandle");
        HttpSession session = req.getSession();
        Object uname = session.getAttribute("user");
        if (uname != null) {
            // 用户已经登陆，放行
            return true;
        }
        // 跳转到登陆页面
        resp.sendRedirect(req.getContextPath()+"/login.jsp");
        return false;
    }
}

2，在springmvc.xml里面注册

自定义拦截器