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 ExceptionFilter implements Filter {

    protected FilterConfig filterConfig = null;

    private static final String PAGE_TO_FORWARD = "errorNew.jsp";

    // ---------------------- Public Methods
    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        HttpServletRequest request = (HttpServletRequest) req;
        HttpSession session = request.getSession();
        Exception e=null;
        long millsecds=0;
        
        millsecds=System.currentTimeMillis();
        
        try {
            chain.doFilter(req, res);
        }catch(NullPointerException ee){            
            e=ee;
            session.setAttribute("msg", "空指针异常!异常编号是:"+millsecds);
        } catch (Exception ee) {
            e=ee;
            session.setAttribute("msg", "异常!异常编号是:"+millsecds);            
        }
        //把异常信息保存到
        saveExceptionToDataBase(e,millsecds);
        session.setAttribute("e", e);
        redirect(PAGE_TO_FORWARD, request, response);

    }

    public void init(FilterConfig filterConfig) {

    }

    public void destroy() {
    }

    // --------------------- Private Methods
    private void redirect(String page, HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        response.sendRedirect(request.getContextPath() + "/" + page);
    }
    private void saveExceptionToDataBase(Exception e,long millsecds){
        //把异常保存到db中
    }
}