網上圖書商城10--前臺登錄過濾器

前臺中某些位置可以不登陸就可以訪問，而還有一些模塊只有登入用戶才能訪問！

哪些模塊只有登錄用戶才能訪問：

1.購物車     jsp:/jsp/cart/*   servlet:CartItemServlet

2.訂單        jsp:/jsp/order/*   servlet:OrderServlet

1.web.xml

<filter>
	<filter-name>LoginFilter</filter-name>
	<filter-class>cn.itcast.goods.web.filter.LoginFilter</filter-class>
</filter>
<filter-mapping>
	<filter-name>LoginFilter</filter-name>
	<url-pattern>/jsps/cart/*</url-pattern>
</filter-mapping>
<filter-mapping>
	<filter-name>LoginFilter</filter-name>
	<servlet-name>CartItemServlet</servlet-name>
</filter-mapping>
<filter-mapping>
	<filter-name>LoginFilter</filter-name>
	<url-pattern>/jsps/order/*</url-pattern>
</filter-mapping>
<filter-mapping>
	<filter-name>LoginFilter</filter-name>
	<servlet-name>OrderServlet</servlet-name>
</filter-mapping>

2.LoginFilter

public void doFilter(ServletRequest request, ServletResponse response,
		FilterChain chain) throws IOException, ServletException {
	/*
	 * 1. 獲取session中的user
	 * 2. 判斷是否為null
	 *   > 如果為null：保存錯誤信息，轉發到msg.jsp
	 *   > 如果不為null：放行
	 */
	HttpServletRequest req = (HttpServletRequest) request;
	Object user = req.getSession().getAttribute("sessionUser");
	if(user == null) {
		req.setAttribute("code", "error");//為了顯示X圖片
		req.setAttribute("msg", "您還沒有登錄，不能訪問本資源");
		req.getRequestDispatcher("/jsps/msg.jsp").forward(req, response);
	} else {
		chain.doFilter(request, response);//放行
	}
}