package com.jspdev;
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 SignonFilter implements Filter{
    final private String LOGIN_PAGE= "http://www.sina.com.cn";
    protected FilterConfig filterConfig;
    /* (non-Javadoc)
     * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
     */
    public void init(FilterConfig config) throws ServletException {
        // TODO Auto-generated method stub
        this.filterConfig = config;
    }

    /* (non-Javadoc)
     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
     */
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        HttpServletRequest hreq = (HttpServletRequest)req;
        HttpServletResponse hres = (HttpServletResponse)res;
        String isLogin = "";
        HttpSession session = hreq.getSession();
        try{
            isLogin = session.getAttribute("isLogin").toString();
            if(isLogin.equals("ture"))
            {
                System.out.println("access valid");
                chain.doFilter(req,res);
                }
            else{
                hres.sendRedirect(LOGIN_PAGE);  //就是此处转向的
                }
        }
        catch(Exception e)
        {
            e.printStackTrace();
            }
    }

    /* (non-Javadoc)
     * @see javax.servlet.Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
        this.filterConfig = null;
    }
    public void setFilterConfig(final FilterConfig filterConfig)
    {
        this.filterConfig = filterConfig;
        }

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
HttpServletRequest hreq = (HttpServletRequest)req;
HttpServletResponse hres = (HttpServletResponse)res;
String isLogin = "";
HttpSession session = hreq.getSession();
try{
isLogin = String.valueOf(session.getAttribute("isLogin"));//你那样写会有空指针错误。
if(isLogin.equals("ture"))
{
System.out.println("access valid");
chain.doFilter(req,res);
}
else{
hres.sendRedirect(LOGIN_PAGE); //就是此处转向的
}
}
catch(Exception e)
{
e.printStackTrace();
}
}