Online Book Mall 11--Backend Login Filter

<filter>
	<filter-name>AdminLoginFilter</filter-name>
	<filter-class>cn.itcast.goods.admin.web.filter.AdminLoginFilter</filter-class>
</filter>
<filter-mapping>
	<filter-name>AdminLoginFilter</filter-name>
	<url-pattern>/adminjsps/admin/*</url-pattern>
	<url-pattern>/admin/*</url-pattern>
</filter-mapping>

public void doFilter(ServletRequest request, ServletResponse response,
		FilterChain chain) throws IOException, ServletException {
	HttpServletRequest req = (HttpServletRequest) request;
	Object admin = req.getSession().getAttribute("admin");
	if(admin == null) {
		request.setAttribute("msg", "您还没有登录，不要瞎遛达！");
		request.getRequestDispatcher("/adminjsps/login.jsp").forward(request, response);
	} else {
		chain.doFilter(request, response);
	}
}