javaweb 簡單驗證過濾器防止未登錄直接進入主頁

---LoginFilter.java

import java.io.IOException;
 
 import javax.servlet.Filter;
 import javax.servlet.FilterChain;
 import javax.servlet.FilterConfig;
 import javax.servlet.ServletException;
 import javax.servlet.ServletRequest;
 import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import javax.servlet.http.HttpSession;
 
 public class LoginFilter implements Filter {
 
     @Override
     public void init(FilterConfig filterConfig) throws ServletException {
         // TODO Auto-generated method stub
 
     }
 
     @Override
     public void doFilter(ServletRequest request, ServletResponse response,
             FilterChain chain) throws IOException, ServletException {
         // 獲得在下面代碼中要用的request,response,session對象
         HttpServletRequest servletRequest = (HttpServletRequest) request;
         HttpServletResponse servletResponse = (HttpServletResponse) response;
         HttpSession session = servletRequest.getSession();
 
         // 獲得用戶請求的URI
         String path = servletRequest.getRequestURI();
         //System.out.println(path);
         
         // 從session裏取員工工號信息
         String empId = (String) session.getAttribute("empId");
 
         /*創建類Constants.java，裏面寫的是無需過濾的頁面
         for (int i = 0; i < Constants.NoFilter_Pages.length; i++) {
 
             if (path.indexOf(Constants.NoFilter_Pages[i]) > -1) {
                 chain.doFilter(servletRequest, servletResponse);
                 return;
             }
         }*/
         
         // 登陸頁面無需過濾
         if(path.indexOf("/login.jsp") > -1) {
             chain.doFilter(servletRequest, servletResponse);
             return;
         }
 
         // 判斷如果沒有取到員工信息,就跳轉到登陸頁面
         if (empId == null || "".equals(empId)) {
             // 跳轉到登陸頁面
             servletResponse.sendRedirect("/JingXing_OA/login.jsp");
         } else {
             // 已經登陸,繼續此次請求
             chain.doFilter(request, response);
         }
 
     }
 
     @Override
     public void destroy() {
         // TODO Auto-generated method stub
 
     }
 
 }



web.xml 配置
 <!-- 配置登陸過濾器 -->
 <filter>
         <filter-name>login</filter-name>
         <filter-class>LoginFilter</filter-class>
     </filter>
 
     <filter-mapping>
         <filter-name>login</filter-name>
         <url-pattern>/*</url-pattern>
 </filter-mapping>