过滤器(登录认证)

过滤器(登录认证)

登录认证
　　删除用户信息, 修改用户信息, 查看用户信息, 等操作, 需要登录验证,
　　这种验证可以使用过滤器统一处理.

Demo: 登录认证
　　1.定义过滤器

public class LoginFilter implements Filter{
    @Override
    public void destroy() {
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        //向下转型
        HttpServletRequest req = (HttpServletRequest)request;
        HttpServletResponse resp = (HttpServletResponse)response;
        //判断用户是否登录
        if (req.getSession().getAttribute("username")==null) {
            //没有登录则跳转到登录页面
            req.setAttribute("msg", "请登录在修改");
            req.getRequestDispatcher("/pages/login.jsp").forward(req, resp);
        } else {
            //放行请求
            chain.doFilter(req, resp);
        }
    }
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
}

2.修改配置文件

  <!-- 配置过滤器 -->
  <filter>
      <filter-name>lgFilter </filter-name>
      <filter-class>com.sxt.mvcpro.filter.LoginFilter </filter-class>
  </filter>
  <filter-mapping>
      <filter-name>lgFilter </filter-name>
      <!-- 过滤器处理所有的路径 -->
      <url-pattern>/emp/delete</url-pattern>
      <url-pattern>/emp/update</url-pattern>
      <url-pattern>/emp/list</url-pattern>
      <url-pattern>/emp_list.jsp</url-pattern>
      <url-pattern>/dept/list</url-pattern>
  </filter-mapping>