求助帖！各位大大帮帮忙！关于网站退出登录的问题！

[_o小怪兽o_]

我用jsp做了一个网站，现在最后一块的 退出登录 模块我是 一个超链接到 servlet后台 执行 request.getSession().invalidate(); 将session销毁！然后退出到登陆页面。但是现在有一个问题就是：我点击浏览器的后退按钮还是可以返回到我前面浏览过得网页，我听说可以在每一个页面写一个验证，验证session是否为空，但是我试了很多方法都没有达到想要的效果，就是页面验证session为空就跳转到登录页面。求给位大大多多指导，有范例代码最好，让小弟拜读一下！谢谢了！

[Tommyzcg]

写个监听器，配置到web.xml中，如下，或者直接在页面判断

HashMap userbean = (HashMap)session.getAttribute("userbean");
if(userbean !=null){
这里是页面内容
}else{
response.sendRedirect("/login.jsp");
}%>

<filter>
		<filter-name>UrlFilter</filter-name>
		<filter-class>jerehnet.filters.AuthorizationFilter</filter-class>
		<init-param>
			<param-name>loginPage</param-name>
			<param-value>/login.jsp</param-value>
		</init-param>
		<!-- 例外情况 -->
		<init-param>
			<param-name>noUrlPage</param-name>
			<param-value>/login.jsp</param-value>
		</init-param>
	</filter>		

package jerehnet.filters;

import java.io.IOException;
import java.util.HashMap;

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 AuthorizationFilter implements Filter {

	private String loginPage;
	private String[] noUrlPage;
	
	public void init(FilterConfig filterConfig) throws ServletException 
	{
		loginPage = filterConfig.getInitParameter("loginPage");
		noUrlPage = filterConfig.getInitParameter("noUrlPage").split(",");
	}

	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest req = (HttpServletRequest) request;
		HttpServletResponse res = (HttpServletResponse) response;
		HttpSession session = req.getSession();
		HashMap adminUser = (HashMap) session.getAttribute("adminUser");
		String pageurl = req.getServletPath();
		if (adminUser == null)
		{
			boolean login = false;
			for (String url : noUrlPage) 
			{
				if (pageurl.equals(url)) 
				{
					login = true;
					break;
				}
			}
			if(login)
			{
				chain.doFilter(request, response);
			}
			else {
				res.sendRedirect(loginPage);
			}
			
		} else 
		{
			chain.doFilter(request, response);
		}

		req = null;
		res = null;
		session = null;
		adminUser = null;
	}

	public void destroy() {
	}
}