在Web.xml中增加个配置过滤器loginFilter：
1 <filter>
2 <filter-name>loginFilter</filter-name>
3 <filter-class>com.filter.LoginFilter</filter-class>
4 </filter>
5 <filter-mapping>
6 <filter-name>loginFilter</filter-name>
7 <url-pattern>/*</url-pattern>
8 </filter-mapping>
在处理登陆的action中,登陆成功后,往session中写入一个值,作为是否登陆的标记,这里写入用户名username:
1 HttpServletRequest request = ServletActionContext.getRequest();
2 request.getSession().setAttribute("username", username);
然后编辑相应的过滤器类LoginFilter,过滤器检查session中username的值是否为空,为空则跳转至登陆页面：
1 package com.filter;
2
3 import java.io.IOException;
4 import javax.servlet.Filter;
5 import javax.servlet.FilterChain;
6 import javax.servlet.FilterConfig;
7 import javax.servlet.ServletException;
8 import javax.servlet.ServletRequest;
9 import javax.servlet.ServletResponse;
10 import javax.servlet.http.HttpServlet;
11 import javax.servlet.http.HttpServletRequest;
12 import javax.servlet.http.HttpServletResponse;
13 import javax.servlet.http.HttpSession;
14
15 public class LoginFilter extends HttpServlet implements Filter {
16 public void destroy() {
17 }
18
19 public void doFilter(ServletRequest sRequest, ServletResponse sResponse,
20 FilterChain filterChain) throws IOException, ServletException{
21
22 HttpServletRequest request = (HttpServletRequest) sRequest;
23 HttpServletResponse response = (HttpServletResponse) sResponse;
24 HttpSession session = request.getSession();
25 String url=request.getServletPath();
26 String contextPath=request.getContextPath();
27 if(url.equals("")) url+="/";
28 if((url.startsWith("/")&&!url.startsWith("/login"))){//若访问后台资源 过滤到login
29 String user=(String)session.getAttribute("username");
30 if(user==null){//转入管理员登陆页面
31 response.sendRedirect(contextPath+"/login.jsp");
32 return;
33 }
34 }
35 filterChain.doFilter(sRequest, sResponse);
36 }
37
38 public void init(FilterConfig arg0) throws ServletException {
39
40 }
41 }
这样就可以了,除了login页面外全部都会被过滤器检测。
注：
浏览器关闭后session将被销毁，用户需重新登陆。
退出操作则将session中的username值设置为null即可。