过滤器案例: 登录验证(权限校验)

迷南。 2022-12-24 13:59 148阅读 0赞

# 需求 #

1.访问项目的资源。验证其是否登录  
2.如果登录了，则直接放行。  
3.如果没有登录，则跳转到登录页面

# 代码实现 #

**登录界面**

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
      <head>
        <title>$Title$</title>
      </head>
      <body>
      <form action="treeServlet" method="post">
        账号：<input type="text" name="username"><br>
        密码：<input type="text" name="pass"><br>
        <input type="submit">
      </form>
      </body>
    </html>

**servlet**

package com.bdit.servlet;
    
    import com.bdit.sevice.TreeSevice;
    import com.bdit.vo.Tree;
    import com.mysql.cj.Session;
    
    
    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 javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    @WebServlet(urlPatterns = {
        "/treeServlet"})
    public class TreeServlet extends HttpServlet {
        
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
            HttpSession session=req.getSession();
            session.removeAttribute("a");
            req.getRequestDispatcher("index.jsp").forward(req,resp);
            doPost(req, resp);
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
            String username=req.getParameter("username");
            String pass=req.getParameter("pass");
            TreeSevice sevice=new TreeSevice();
            //根据用户名和密码查询数据库是否有符合条件的数据
            Tree tree=sevice.find(username,pass);
            if(tree!=null&&tree.getUsername().equals(username)&&tree.getPass().equals(pass)){
        
                HttpSession session= req.getSession();
                session.setAttribute("a","ok");
                resp.sendRedirect("success.jsp");
            }else{
        
                resp.sendRedirect("error.jsp");
            }
        }
    }

**过滤器**

package com.bdit.filter;
    
    import javax.servlet.*;
    import javax.servlet.annotation.WebFilter;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    @WebFilter(urlPatterns = {
        "/safe/*"})
    public class TreeFilter implements Filter {
        
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        
            servletRequest.setCharacterEncoding("UTF-8");
            servletResponse.setContentType("test/html;charset=UTF-8");
            HttpServletRequest request= (HttpServletRequest) servletRequest;
            HttpServletResponse response= (HttpServletResponse) servletResponse;
    
            HttpSession se= request.getSession();
            Object session=request.getSession(false);
            if(session==null || se.getAttribute("a")==null){
        
                response.sendRedirect(request.getContextPath()+"/index.jsp");
            }else{
        
                filterChain.doFilter(request,response);
            }
    
        }
    }

**登录之后才能访问的页面**  
此页面路径：  
![在这里插入图片描述][20201128205721898.png_pic_center]

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <h2>登录之后可以访问此页面</h2>
    <%
        HttpSession session1= request.getSession();
        Object se=request.getSession();
        String a= (String) session1.getAttribute("a");
    %>
    <%=a%>
    </body>
    </html>

[20201128205721898.png_pic_center]: /images/20221120/fc560e4805c848449b46e0adbe3aa11b.png