JavaWeb_检查用户是否登录的过滤器

「爱情、让人受尽委屈。」 2023-08-17 17:41 137阅读 0赞

## 检测用户是否登录的过滤器： ##

**——情景：系统中某些页面只有在正常登录后才可以使用，用户请求这些页面时要检查session中有无该用户信息，但在所有必要的页面加上session的判断相当麻烦的事情**

**——解决方案：编写一个用于检测用户是否登录的过滤器，如果用户未登录，则重定向到指定的登录页面**

**——要求：需检查的在Session中保存的关键字；如果用户未登录，需重定向到指定的页面(URL不包括ContextPath)；不做检查的URL列表(以分号分开，并且URL中不包括ContextPath)都要采取可配置的方式。**

**list.jsp**

![1642540-20190718161151822-442146799.png][]

**设置b,c,d,e需要用户登录权限，点击跳转login.jsp**

![1642540-20190718161254391-2002211463.png][]

**登录完成，输入有效的名字可以进入其他页面**

![1642540-20190718161348196-1848397947.png][]

**源代码：**

**list.jsp**

**a,b,c,d,e.jsp**

<h4>AAA PAGE</h4>
    <a href="list.jsp">Return...</a>

**login.jsp**

<form action="doLogin.jsp" method="post">
        username: <input type="text" name="username">
        <input type="submit" value="Submit">
    </form>

**doLogin.jsp**

<%
            //1.获取用户的登录信息
            String username = request.getParameter("username");
    
            //2.若登录信息完整，则把登录信息方法HttpSession
            if (username!=null&&!username.trim().equals("")){
                session.setAttribute(application.getInitParameter("userSessionKey"),username);
                //3.重定向到list.jsp
                response.sendRedirect("list.jsp");
            }else {
                response.sendRedirect("login.jsp");
            }
        %>

**web.xml的相关设置**

<context-param>
            <param-name>userSessionKey</param-name>
            <param-value>USERSESSIONKEY</param-value>
        </context-param>
        
        
        <context-param>
            <param-name>rediretPage</param-name>
            <param-value>/login/login.jsp</param-value>
        </context-param>
    
        
        <context-param>
            <param-name>uncheckedUrls</param-name>
            <param-value>/login/a.jsp,/login/list.jsp,/login/login.jsp,/login/doLogin.jsp,</param-value>
        </context-param>

**LoginFilter.java**

package com.demo.filter;
    
    import javax.servlet.*;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.util.Arrays;
    import java.util.List;
    
    public class LoginFilter implements Filter {
    
        private String sessionKey;
        private String redirectUrl;
        private String uncheckedUrls;
        private FilterConfig filterConfig;
    
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
            this.filterConfig = filterConfig;
            ServletContext servletContext = this.filterConfig.getServletContext();
            sessionKey = servletContext.getInitParameter("userSessionKey");
            redirectUrl = servletContext.getInitParameter("rediretPage");
            uncheckedUrls  = servletContext.getInitParameter("uncheckedUrls");
    
            System.out.println(sessionKey);
            System.out.println(redirectUrl);
            System.out.println(uncheckedUrls);
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
             HttpServletRequest request = (HttpServletRequest) servletRequest;
             HttpServletResponse response = (HttpServletResponse) servletResponse;
            //1.从web.xml文件中获取sessionKey，redirectUrl,uncheckedUrls
               //1.获取请求的servletPath
                String requestUrl = request.getRequestURL().toString();
                String requestUri = request.getRequestURI();
                String servletPath = request.getServletPath();
    //          http://localhost:8081/javaweb/login/list.jsp
                System.out.println(requestUrl);
    //            /javaweb/login/list.jsp
                System.out.println(requestUri);
    //            /login/list.jsp
                System.out.println(servletPath);
                //2.检查1获取的servletPath是否不需要检查的URL中的一个，若是，则直接放行，方法结束
                List<String> urls = Arrays.asList(uncheckedUrls.split(","));
                if (urls.contains(servletPath)){
                    filterChain.doFilter(request,response);
                    return;
                }
    
                //3.从session中获取sessionKey对应的值，若值不存在，则重定向到redirectUrl
                Object user = request.getSession().getAttribute(sessionKey);
                if (user == null){
                    response.sendRedirect(request.getContextPath()+ redirectUrl);
                    return;
                }
    
                //4.若存在，则放行，允许访问
                filterChain.doFilter(request,response);
    
        }
    
        @Override
        public void destroy() {
    
        }
    }

转载于:https://www.cnblogs.com/yangHS/p/11201084.html

[1642540-20190718161151822-442146799.png]: /images/20230808/5d54a9af16954923941920642b12a9e8.png
[1642540-20190718161254391-2002211463.png]: /images/20230808/6df4a863e33e4e8ba59c78c1dec25e48.png
[1642540-20190718161348196-1848397947.png]: /images/20230808/9c46e7f3fb2f4a2e82ea533e50335408.png