[codes=java]
/**
*
*/
package cn.org.jock.filter;

import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.FilterChain;
import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletResponse;

/**
* @author jock
*
*/
public class AuthorizationFilter implements Filter {

 /*
  * (non-Javadoc)
  *
  * @see javax.servlet.Filter#destroy()
  */
 public void destroy() {
   // TODO Auto-generated method stub

 }

 /*
  * (non-Javadoc)
  *
  * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest,
  *      javax.servlet.ServletResponse, javax.servlet.FilterChain)
  */
 public void doFilter(ServletRequest request, ServletResponse response,
     FilterChain chain) throws IOException, ServletException {
   HttpServletRequest req = (HttpServletRequest) request;
   HttpServletResponse res = (HttpServletResponse) response;

   HttpSession session = req.getSession(true);

   String username = (String) session.getAttribute("username");

   if (username == null || "".equals(username)) {
     // 跳转到登陆页面
     res.sendRedirect("/login.jsp");
   } else {
     chain.doFilter(request, response);
   }

 }

 /*
  * (non-Javadoc)
  *
  * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
  */
 public void init(FilterConfig arg0) throws ServletException {
   // TODO Auto-generated method stub

 }

}

[/codes]


web.xml里对需要登陆验证的进行配置
[codes=xml]

 ...
 
   authorization
   cn.org.jock.filter.AuthorizationFilter
 

 
   authorization
   /abc/*
 
 ...


[/codes]