利用HttpModuler实现 WEB程序同一时间只让一个用户 登陆

在不影响原来的整个网站 的情况下,可以使用了HttpModuler来实现:

先让所有的Page从自己的Page类：BasePage类继承，并实现 ISigleLogin接口

 

     public   interface  ISingleLogin
     ... {
        string SigleUserLoginId ...{ get; }

        void SigleUserLogout();

    }

 

public   class  BasePage : System.Web.UI.Page , BNet.Web.Modulers.ISingleLogin
... {
    public BasePage()
    ...{
        //
        // TODO: 在此处添加构造函数逻辑
        //
    }

    protected override void OnLoad(EventArgs e)
    ...{
        base.OnLoad(e);
        if (Session["UserId"] == null)
        ...{
            Response.Write("你还没有登陆");
            Response.Redirect("login.aspx");
        }
    }

    ISingleLogin 成员ISingleLogin 成员#region ISingleLogin 成员

    public string SigleUserLoginId
    ...{
        get 
        ...{
            if (Session["UserId"] != null)
            ...{
                return Session["UserId"].ToString();
            }
            else
                return "";
        }
    }

    public void SigleUserLogout()
    ...{
        Session.Abandon();
        Response.Write("你在别处已经登陆，强制退出本次登陆!");
    }

    #endregion
}

然后在Web.config中加入HttpModuler：

< system .web >
     < httpModules >
       < add  name ="SingleLogin"  type ="BNet.Web.Modulers.SingleLoginModuler" />

     </ httpModules >
</ system.web >

相关的SigleLoginModuler代码如下：

using  System;
using  System.Collections.Generic;
using  System.Data;
using  System.Configuration;
using  System.Web;
using  System.Web.UI;

namespace  BNet.Web.Modulers
... {
    /**//**//**//// <summary>
    /// SingleLoginModuler 的摘要说明
    /// </summary>
    public class SingleLoginModuler : System.Web.IHttpModule
    ...{
        const string sigle_login_userid = "evlon_siglelogin_userid";
        const string sigle_pre_logout_sessionid = "evlon_sigle_pre_logout_sessionid";

        public static StringLifeValueDictionary UsableGetter(ref StringLifeValueDictionary dic)
        ...{
            if (dic == null)
            ...{
                dic = new StringLifeValueDictionary();
            }
            else
            ...{
                List<string> listRemove = new List<string>();
                StringLifeValueDictionary.Enumerator iter = dic.GetEnumerator();
                while (iter.MoveNext())
                ...{
                    if (iter.Current.Value.life < DateTime.Now)
                    ...{
                        listRemove.Add(iter.Current.Key);
                    }
                }

                foreach (string key in listRemove)
                ...{
                    dic.Remove(key);
                }
            }

            return dic;
        }

        static StringLifeValueDictionary loginedUserIdDictionary = null;
        static StringLifeValueDictionary LoginedUserIdDictionary
        ...{
            get
            ...{
                return UsableGetter(ref loginedUserIdDictionary);
            }
        }

        static StringLifeValueDictionary preLogoutSessionIdDictionary = null;
        static StringLifeValueDictionary PreLogoutSessionIdDictionary
        ...{
            get
            ...{
                return UsableGetter(ref preLogoutSessionIdDictionary);
            }
        }

        public SingleLoginModuler()
        ...{
            //
            // TODO: 在此处添加构造函数逻辑
            //
        }

        IHttpModule 成员IHttpModule 成员#region IHttpModule 成员

        public void Dispose()
        ...{
        }

        public void Init(HttpApplication context)
        ...{
            context.PreRequestHandlerExecute += new EventHandler(context_PreRequestHandlerExecute);
            context.PostRequestHandlerExecute += new EventHandler(context_PostRequestHandlerExecute);

        }



        void context_PreRequestHandlerExecute(object sender, EventArgs e)
        ...{
            HttpApplication context = sender as HttpApplication;
            IHttpHandler httpHandler = context.Context.CurrentHandler;
            ISingleLogin sl = httpHandler as ISingleLogin;
            if (sl != null)
            ...{
                string suid = sl.SigleUserLoginId;
                if (suid != string.Empty)
                ...{
                    if (PreLogoutSessionIdDictionary.ContainsKey(context.Session.SessionID))
                    ...{
                        //这个用户应该强制登出
                        PreLogoutSessionIdDictionary.Remove(context.Session.SessionID);

                        Page page = (Page)httpHandler;
                        page.PreInit += new EventHandler(page_PreInit);

                    }
                    else if (!LoginedUserIdDictionary.ContainsKey(suid))
                    ...{
                        LoginedUserIdDictionary.Add(suid, new LifeValue(context.Session.SessionID));
                    }
                }
            }

        }

        void page_PreInit(object sender, EventArgs e)
        ...{
            Page page = sender as Page;
            ISingleLogin sl = page as ISingleLogin;
            if (sl != null)
            ...{
                sl.SigleUserLogout();
                page.Response.End();
            }
        }

        void context_PostRequestHandlerExecute(object sender, EventArgs e)
        ...{
            //从LogineduserId 里找到和当前用户一样的用户ID的SessionId
            HttpApplication context = sender as HttpApplication;
            IHttpHandler httpHandler = context.Context.CurrentHandler;
            ISingleLogin sl = httpHandler as ISingleLogin;
            if (sl != null)
            ...{
                string suid = sl.SigleUserLoginId;
                if (suid != string.Empty)
                ...{
                    if (LoginedUserIdDictionary.ContainsKey(suid))
                    ...{
                        string sessionId = LoginedUserIdDictionary[suid].value;
                        if (sessionId != context.Session.SessionID)
                        ...{
                            if (!PreLogoutSessionIdDictionary.ContainsKey(sessionId))
                            ...{
                                PreLogoutSessionIdDictionary.Add(sessionId, new LifeValue(suid));
                            }

                            LoginedUserIdDictionary.Remove(suid);
                        }
                    }
                    else
                    ...{
                        LoginedUserIdDictionary.Add(sl.SigleUserLoginId, new LifeValue(context.Session.SessionID));
                    }

                }
            }
        }

        #endregion
    }

    public class LifeValue
    ...{
        public string value;
        public DateTime life;

        public LifeValue(string value)
        ...{
            this.value = value;
            this.life = DateTime.Now.AddMinutes(HttpContext.Current.Session.Timeout + 5);
        }
    }

    public class StringLifeValueDictionary : Dictionary<string, LifeValue>
    ...{

    }


    public interface ISingleLogin
    ...{
        string SigleUserLoginId ...{ get; }

        void SigleUserLogout();

    }
}

   如此，只在在你自己的BasePage中改动相关的代码（只两三行）就可以实现功能了。

前面的代码也可以:

if (httpHandler is ISingleLogin)
{
ISingleLogin sl = httpHandler as ISingleLogin;

这个代码通常写为

if (httpHandler is ISingleLogin)
{
ISingleLogin sl = (ISingleLogin) httpHandler;

效率高一点，因为前面已经用过 is 判断了，强制类型转换是安全的。

static StringLifeValueDictionary LoginedUserIdDictionary
static StringLifeValueDictionary PreLogoutSessionIdDictionary

这两个属性的读写逻辑是完全一样的，有重复的 bad smell，可以重构为一个同样的 getter 方法。

用C#1.1的语法来实现 :
StringLifeValueDictionary

替换　List<string> 为　StringCollection

其它的，就没有了什么了

// public class StringLifeValueDictionary : Dictionary<string, LifeValue>
     // {

     // }

     public   class  StringLifeValueDictionary : System.Collections.DictionaryBase
     ... {
        public LifeValue this[string key]
        ...{
            get 
            ...{
                return (LifeValue)this.Dictionary[key];
            }
            set
            ...{
                this.Dictionary[key] = value;
            }
        }

        public void Add(string key, LifeValue value)
        ...{
            this.Dictionary.Add(key, value);
        }

        public bool Contains(string key)
        ...{
            return this.Dictionary.Contains(key);
        }

        public void Remove(string key)
        ...{
            this.Dictionary.Remove(key);
        }

        public bool ContainsKey(string key)
        ...{
            return this.Dictionary.Contains(key);
        }

        public IDictionaryEnumerator GetEnumerator()
        ...{
            return this.Dictionary.GetEnumerator();
        }

    }

// StringLifeValueDictionary.Enumerator iter = dic.GetEnumerator();
                 // while (iter.MoveNext())
                 // {
                 //     if (iter.Current.Value.life < DateTime.Now)
                 //     {
                 //         listRemove.Add(iter.Current.Key);
                 //     }
                 // }

                IDictionaryEnumerator iter  =  dic.GetEnumerator();
                 while  (iter.MoveNext())
                 ... {
                    if (((LifeValue)iter.Entry.Value).life < DateTime.Now)
                    ...{
                        listRemove.Add((string)iter.Entry.Key);
                    }
                }

分别修改上面的两处