如何用过滤器拦截未登录直接访问资源页面

红太狼 2023-01-12 11:53 199阅读 0赞

## 如何用过滤器拦截未登录直接访问资源页面 ##

**登录界面 login.jsp：**

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <form action="login" method="post">
            用户名:<input type="text" name="username"><br>
            密码：<input type="password" name="password"><br>
            <input type="submit" value="提交"><br>
        </form>
    </body>
    </html>

**登录成功后页面 index.jsp:**

**登录servlet：**

@WebServlet("/login")
    public class LoginServlet extends HttpServlet { 
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            //获得用户信息
            String username = req.getParameter("username");
            String password = req.getParameter("password");
            //验证用户
            if("yang".equals(username) && "123".equals(password)){ 
                req.getSession().setAttribute("username",username);
                resp.sendRedirect("index.jsp");
                return;
            }
            //登录失败 跳转到登录页面
            resp.sendRedirect("login.jsp");
        }
    }

**过滤器：**

@WebFilter("/*")
    public class MyFilter implements Filter { 
        @Override
        public void init(FilterConfig filterConfig) throws ServletException { }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { 
            //向下转型
            HttpServletRequest request=(HttpServletRequest)servletRequest;
            HttpServletResponse response=(HttpServletResponse)servletResponse;
            //获得请求uri
            String requestURI = request.getRequestURI();
            System.out.println(requestURI);
            //判断请求是否为登录请求  是则放行
            if("/login.jsp".equals(requestURI) || "/login".equals(requestURI)){ 
                System.out.println("ok");
                filterChain.doFilter(request,response);
                return;
            }
            //获得session域中username
            Object username = request.getSession().getAttribute("username");
            //判断是否有用户名 没有就跳回登录页面
            if(username==null){ 
                response.sendRedirect("login.jsp");
                return;
            }
            //放行
            filterChain.doFilter(request,response);
        }
    
        @Override
        public void destroy() { }
    }