SSM------------------SpringMVC的拦截器

public class LoginInterceptor implements HandlerInterceptor{

      //controller执行后且视图返回后调用此方法

      public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)

                  throws Exception {

            System.out.println("返回视图前  后处理");

      }

      //controller执行后但未返回视图前调用此方法

      public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)

                  throws Exception {

            System.out.println("未返回视图前 后处理....");

      }

      // controller执行前调用此方法

      public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object obj) throws Exception {

            // TODO Auto-generated method stub

            System.out.println("预处理....");

            //如果是登录页面则放行

            if(request.getRequestURI().indexOf("login.do")>=0){

                  return true;

            }

            HttpSession session = request.getSession();

            //如果用户已登录也放行

            if(session.getAttribute("user")!=null){

                  return true;

            }

            //用户没有登录挑战到登录页面

            request.getRequestDispatcher("/WEB-INF/views/login.jsp").forward(request, response);

            return false;

      }

}