Session超时跳转到指定页面（filter实现）解决了图片被过滤问题

package com.myplan.checkloginfilter;

import javax.servlet.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

/**
* 用于检测用户是否登陆的过滤器，如果未登录或超时，则重定向到指的登录页面<p>
*/
public class CheckLoginFilter extends HttpServlet implements Filter {

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain filterChain) {
try {
HttpServletRequest hsr = (HttpServletRequest) request;
HttpSession session = hsr.getSession();
if (hsr.getRequestURI().startsWith(
hsr.getContextPath() + "/login.jsp")
|| hsr.getRequestURI().startsWith(
hsr.getContextPath() + "/login.do")
|| hsr.getRequestURI().equals(hsr.getContextPath() + "/")
) {
// 请求登陆页面，所以放过
System.out.println("放过login");
filterChain.doFilter(request, response);
} else {
if (session.getAttribute("employeeEmail") != null) {
//这里session存在，那么则登陆，放过session
// 已登录，放过请求
System.out.println("test filter chain");
filterChain.doFilter(request, response);
} else {
//session超期后，自然session就是空了，那么则跳转到指定的页面就可以了
// 未登录，跳转到登录页

PrintWriter out = response.getWriter();
out.print("<script>window.top.location.href='http://blog.163.com/girl_lihuiyue@126/blog/"
+ hsr.getContextPath() + "';</script>");
}
}
} catch (ServletException sx) {
} catch (IOException iox) {
}
}

public void destroy() {

}

public void init(FilterConfig filterConfig) throws ServletException {

}
}

<filter>
<filter-name>CheckLoginFilter</filter-name>
<filter-class>com.myplan.checkloginfilter.CheckLoginFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CheckLoginFilter</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
<span style="color:#FF0000;">如果使用session的话，配置
<session-config>
<!-- 以分钟为单位 -->
<session-timeout>30</session-timeout>
</session-config></span>