jsp页面权限设置问题
  在jsp页面中来设置权限，这里用Filter的方式来设置页面权限。下面举的例是一个简单用户登陆注册的例子，所以注册页面和登录页面是用户不用登陆就可以进去查看的。例子如下：
package com.itjob.filter;

import java.io.IOException;
import java.io.PrintWriter;
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 RightFilter implements Filter {
private static final String LOGIN_URI = "LOGIN_URI";
private static final String REG_URI = "REG_URI";


private String login_page;
private String reg_page;

public void destroy() {
}

public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
  HttpServletRequest req = (HttpServletRequest) request;
  HttpServletResponse resp = (HttpServletResponse) response;
  resp.setContentType("text/html;");
  resp.setCharacterEncoding("utf-8");
  HttpSession session = req.getSession();
  PrintWriter out = resp.getWriter();
  // 得到用户请求的URI
  String request_uri = req.getRequestURI();//="/JSPWork/index.jsp"

  // 得到web应用程序的上下文路径
  String ctxPath = req.getContextPath();//="/JSPWork"
  // 去除上下文路径，得到剩余部分的路径
  String uri = request_uri.substring(ctxPath.length());//="index.jsp"
  // 判断用户访问的是否是登录页面
if (uri.equals(login_page) || uri.equals(reg_page)){//注册和登录页面不过滤，如果不这么写，什么页面也进入不了
   chain.doFilter(request, response);
   return;
  } else {
   // 如果访问的不是登录页面，则判断用户是否已经登录
   if (null != session.getAttribute("username")
     && "" != session.getAttribute("username")) {
    chain.doFilter(request, response);
    return;
   } else {
    resp.sendRedirect("/JSPWork/login.jsp");
    return;
   }
  }
}

public void init(FilterConfig config) throws ServletException {
  // TODO Auto-generated method stub
  // 从部署描述符中获取登录页面和首页的URI
  login_page = config.getInitParameter(LOGIN_URI);
  reg_page = config.getInitParameter(REG_URI);
  // System.out.println(logon_page);
  if (null == login_page || null == reg_page) {
   throw new ServletException("没有找到登录页面或主页");
  }
}

}



在web.xml中注意添加以下内容：

<init-param>
     <param-name>LOGIN_URI</param-name>
     <param-value>/login.jsp</param-value>
    </init-param>
    <init-param>
     <param-name>REG_URI</param-name>
     <param-value>/register.jsp</param-value>
   </init-param>