JavaWeb入门案例升级之登录状态验证

1、前言

原版本请访问此链接

2、登录状态验证

功能简介

• 访问所有资源。验证其是否登录
  • 如果登录了，则直接放行。
  • 如果没有登录，则跳转到登录页面，提示”您尚未登录，请先登录”。

分析

代码实现

• LoginFilter.class

  package com.allen.web.filter;
  
  import javax.servlet.*;
  import javax.servlet.annotation.WebFilter;
  import javax.servlet.http.HttpServletRequest;
  import java.io.IOException;
  
  /**
   * 完成登录验证的过滤器
   */
  @WebFilter("/*")
  public class LoginFilter implements Filter {
  
      public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
          //强制转换
          HttpServletRequest request = (HttpServletRequest) req;
  
          //1、获取资源请求路径
          String uri = request.getRequestURI();
          //2、判断是否包含登录相关资源路径,要注意排除掉css/js/图片/验证码等资源
          if(uri.contains("/login.jsp") || uri.contains("/loginServlet") || uri.contains("/css/") || uri.contains("/js/") || uri.contains("/fonts/") || uri.contains("/checkCodeServlet")){
              //包含，用户就是想登录，放行
              chain.doFilter(req, resp);
          }else {
              //不包含，需要验证用户是否登录
              //3、从获取session中获取user
              Object admin = request.getSession().getAttribute("admin");
              if(admin != null){
                  //登录了，放行
                  chain.doFilter(req, resp);
              }else {
                  //没有登录，跳转登录页面
                  request.setAttribute("login_msg","您尚未登录，请登录");
                  request.getRequestDispatcher("/login.jsp").forward(request,resp);
              }
          }
  
      }
  
      public void init(FilterConfig config) throws ServletException {
  
      }
  
      public void destroy() {
      }
  
  }

• login.jsp中加入以下代码

  <c:if test="${pageContext.request.getAttribute('login_msg') == '您尚未登录，请登录'}">
      <div class="alert alert-warning alert-dismissible" role="alert">
          <button type="button" class="close" data-dismiss="alert" >
              <span>&times;</span></button>
          <strong>
              <strong><%=request.getAttribute("login_msg") == null ? "" : "您尚未登录，请登录"%></strong>
          </strong>
      </div>
      <%
          request.getSession().removeAttribute("login_msg");
      %>
  </c:if>

效果展示

• 如果未登录，不管访问除登录页面所需资源外的其他资源均跳转到此页面
  

3、退出登录按钮小功能

分析

代码实现

• index.jsp页面和list.jsp页面分别加入以下代码

  <script>
      function exit() {
          if(confirm("你确定要退出吗？")){
              location.href = "${pageContext.request.contextPath}/userExitServlet";
          }
      }
  </script>
  
  <div>${admin.username}，欢迎您
      <a class="btn btn-default btn-sm" href="javascript:exit();">退出登录</a>
  </div>

• UserExitServlet.class

  package com.allen.web.servlet;
  
  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  
  @WebServlet("/userExitServlet")
  public class UserExitServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.getSession().removeAttribute("admin");
          response.sendRedirect(request.getContextPath()+"/login.jsp");
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

效果展示

点击确定后退出登录，并跳转到登录页面