isenterfilter.java

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package com.xxfb.VIISFilter;

//用来判断用户是否登录，是否可以查看指定的页面

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 IsEnterFilter implements Filter {

	public void init(FilterConfig arg0) throws ServletException {
		// TODO Auto-generated method stub

	}

	public void doFilter(ServletRequest arg0, ServletResponse arg1,
			FilterChain arg2) throws IOException, ServletException {
		// TODO Auto-generated method stub

		HttpServletRequest request = (HttpServletRequest)arg0;
		HttpServletResponse response = (HttpServletResponse)arg1;
		
		HttpSession session = request.getSession();
		String decide = (String)session.getAttribute("isEnter");
		
		if(decide!=null)
		{
			arg2.doFilter(request,response);//如果判断通过则页面继续执行
		}
		else
		{
			response.sendRedirect("/VIIS/login.jsp");//无论出现哪种不通过验证的现象
			//都可以通过这个绝对路径来登录
		}
	}

	public void destroy() {
		// TODO Auto-generated method stub

	}
}