EL表达式取数据注意点

1.从一个页面跳转到另一个页面，需要session保存后再取出数据

LoginServlet doPost()方法

protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {


String user_name=req.getParameter("username");
String password=req.getParameter("password");

HttpSession session=(HttpSession)req.getSession();
session.setAttribute("username", user_name);
session.setAttribute("password", password);

System.out.println("username:"+user_name);
System.out.println("password:"+password);
if(user_name.equals("")||user_name==null)
System.out.println("logininfo fail to transer");
if("admin".equals(user_name)&&"admin".equals(password)){
resp.sendRedirect(req.getContextPath()+"/success.jsp");
}else{
resp.sendRedirect(req.getContextPath()+"/fail.jsp");
}

}

登录成功界面代码

<h1>登录成功！
欢迎
${username}//EL表达式
<%=request.getSession().getAttribute("username") %>//JSP表达式
</h1>