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在 WEB 系統中。 我們通常會用session來儲存一些簡單可是卻非常重要的資訊。比方Asp.net中常常會用Session來儲存使用者登入資訊，比方UserID。為瞭解決 WEB場大家採用了把session存在DB中，session到期大家一般都採用頁面跳轉，即再次登入，login後又返回頁面。
個人認為以上設計不是非常好， 對於web場，假設我們把session存在DB那麼新能應該比存記憶體要慢。所以推薦用分布式緩衝的方式來存取Session。 對於Session到期我建議採用cookie來做。在大型網站中Session應該慎用，畢竟它佔用server的內容。一個人使用者session假設佔用1k的空間，那麼100W使用者同一時候線上 Session要佔用多大空間. 曾經我把userID 直接存cookie會有瀏覽器串cookie的問題，比方我用IE login use1，用FF login user2，發現後面login的user資訊會覆蓋前面login user的值。
回來發現session到期了，可是sessionID還在，而且該值在cookie裡面。
實現code 例如以下：
核心code：
string UserID
{
get
{
if (Session["UserID"] != null)
{
return Session["UserID"].ToString();
}
if (Request.Cookies[Session.SessionID.ToString()] != null)
{
string cv=Request.Cookies[Session.SessionID].Value;
Session["UserID"] = cv;
return cv;
}
return string.Empty;
}
set
{
Session["UserID"] = value;
string key = Session.SessionID.ToString();
HttpCookie kc = new HttpCookie(key, value);
kc.HttpOnly = true;
Response.Cookies.Add(kc);
}
}
public partial class WebForm1 : System.Web.UI.Page { protected void btnSet_Click(object sender, EventArgs e) { Session["name"] = "majiang"; this.lblSet.Text = "Session ID:" + Session.SessionID.ToString(); } protected void btnGet_Click(object sender, EventArgs e) { labGet.Text = "Session ID:" + Session.SessionID.ToString(); if (Session["name"] != null) { labGet.Text += "<br/>" + Session["name"].ToString(); } } Dictionary<string, string> dict = new Dictionary<string, string>(); protected void Page_Load(object sender, EventArgs e) { dict.Add("1", "majiang"); dict.Add("2", "Gavin"); } string UserID { get { if (Session["UserID"] != null) { return Session["UserID"].ToString(); } if (Request.Cookies[Session.SessionID.ToString()] != null) { string cv=Request.Cookies[Session.SessionID].Value; Session["UserID"] = cv; return cv; } return string.Empty; } set { Session["UserID"] = value; string key = Session.SessionID.ToString(); HttpCookie kc = new HttpCookie(key, value); kc.HttpOnly = true; Response.Cookies.Add(kc); } } protected void btnSetwithCookie_Click(object sender, EventArgs e) { UserID = this.txtuserID.Text.Trim(); this.labsetCookie.Text = Session.SessionID.ToString(); } protected void btnGetWithCookie_Click(object sender, EventArgs e) { this.labGetCookie.Text = "Session ID:" + Session.SessionID.ToString(); labGetCookie.Text += "<br/>" + dict[UserID].ToString(); } }
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="SessionTest.WebForm1" %><!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <title></title></head><body> <form id="form1" runat="server"> <div> <asp:Button ID="btnSet" runat="server" Text="Set Session" OnClick="btnSet_Click" /> <asp:Button ID="btnGet" runat="server" Text="Get Session" OnClick="btnGet_Click" /> <br /> SET: <asp:Label ID="lblSet" runat="server" Text=""></asp:Label> <br /> Get: <asp:Label ID="labGet" runat="server" Text=""></asp:Label> </div> userID:<asp:TextBox ID="txtuserID" runat="server"></asp:TextBox> <div> <table> <tr><td><asp:Button ID="btnSetwithCookie" runat="server" Text="Set With Cookie" OnClick="btnSetwithCookie_Click" /></td><td><asp:Button ID="btnGetWithCookie" runat="server" Text="Get With Cookie" OnClick="btnGetWithCookie_Click" /></td></tr> <tr><td><asp:Label ID="labsetCookie" runat="server"></asp:Label> </td><td><asp:Label ID="labGetCookie" runat="server"></asp:Label></td></tr> </table> </div> </form></body></html>
實現的效果
看看HTTP的請求：
大型Web 網站 Asp.net Session到期你怎麼辦
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