直接上代码

@Component
public class LoginHandlerInterceptor implements HandlerInterceptor {

    //目标方法执行之前
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        Object user = request.getSession().getAttribute("currentUser");
        if (user == null) {
            //未登录,返回登录页面
            response.sendRedirect("/LoginError.html");
            return false;
        }else {
            //放行
            return true;
        }
    }
}