spring 用户登录拦截器

public class UserLoginInterceptor extends HandlerInterceptorAdapter {

@Override
public boolean preHandle(HttpServletRequest request,
HttpServletResponse response, Object handler) throws Exception {

System.out.println("UserLoginInterceptor#preHandle...");

HttpSession session = request.getSession();

if (session.getAttribute("User") != null) {
return true;
}

String strBackUrl = "http://" + request.getServerName() + ":"
+ request.getServerPort() + request.getContextPath()
+ request.getServletPath();
if (request.getQueryString() != null) {
strBackUrl += "?" + request.getQueryString();
}
strBackUrl = URLEncoder.encode(strBackUrl, "UTF-8");
response.sendRedirect(request.getContextPath() + "/login?reback="
+ strBackUrl);

System.out.println("UserLoginInterceptor#SESSION IS NULL");
System.out.println("sendRedirect login page!! ");
return false;
}
public void postHandle(HttpServletRequest request,
HttpServletResponse response, Object handler,
ModelAndView modelAndView) throws Exception {
}

public void afterCompletion(HttpServletRequest request,
HttpServletResponse response, Object handler, Exception ex)
throws Exception {
}

}