Home > Others

Whether the user is online (single-point login)

Source: Internet
Author: User
Developer on Alibaba Coud: Build your first app with APIs, SDKs, and tutorials on the Alibaba Cloud. Read more ＞
1. How to determine whether the session has expired.
I have been in contact with JSP for a long time, but I have never thought about this question. At that time, I didn't find a satisfactory answer.
At that time, I mentioned a method to implement the httpsessionlistener interface, and then execute some operations in the sessiondestroyed () method, which indicates that the session will expire because the method is session. method called by the listener before invalidate. This judgment method is obviously not satisfactory.
I asked some people, but I didn't get an accurate answer.
I suddenly realized that the request. getseesion (Boolean) method. In this method, a Boolean value is passed. If this value is true, a new session is created if the current request session is unavailable. If yes, the current session is returned. If the parameter is false, null is returned if the current session of the request does not exist.
In this way, we can easily think of whether the current session of this so-called request has a connection with the session expiration, so we can "approximately" think that the session does not exist because the session has expired, then we can easily determine whether the session has expired. The method is as follows:
If (request. getsession (false) = NULL)
System. Out. println ("session has been invalidated! ");
Else
System. Out. println ("session is active! ");

You may have noticed that there is an "Approximate" word above, that is, there are special situations.
In this special case, when the first request has not yet created a session, the returned value is still null in this method. I think it should be clear to everyone.
Httpservletrequest request = (httpservletrequest) executions. getcurrent (). getnativerequest ();
Httpsession SSN = request. getsession (false );
SSN. setattribute ("name", value );

2. Session destruction
1) Ajax
<Body onUnload = "method ()"> This method cannot be used to delete a session.
2) The Single-point login on the Web end is mainly implemented by recording JSESSIONID to manage sessions, but there are still some problems that cannot be accurately implemented to delete sessions when users exit.

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

Related Keywords:
drupal user login page psql login as user mysql login as user cpanel create user login cpanel user login line user login wordpress user login page

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

What's Trending
Top 10 Tags
datastax versions naming convention zookeeper client class definition md5 microsoft sql server 2005 data structures exception handling error handling
Top 10 Keywords
microsoft download center down wordpress address url site address url wordpress address url windows installer 4 0 download 302 not found web address url definition site address url wordpress db2 integer mac os installation step by step pdf abbreviation for return

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

Get Started for Free

  • Sales Support

    1 on 1 presale consultation

    Chat Contact Sales

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

    Open a Ticket

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.

    Learn More