Web what is a session

Thanks again. Yes, sessions can also be stored in DB or files. Usually its done when user shows no activity for some time but we don't want to sign-out or destroy her session. Sessions synchronizations is another issue, for example 10 servers are serving requests, the first request was served by Server 1, but then it got busy in other users, and the subsequent request from same user sent to Server 4.

Now the session data exist in Server 1, so intelligent techniques are used here to make sure sessions remain synchronized on all servers or same server handle the request. It latest web architectures, e. The details of these issue is out of scope of this post. Yes it is possible but you get a overhead when storing in DB, so its batter to do only for inactive users as very well explained by Asif. I have a simple form submission. It stores some fields in the database.

Post a Comment. Term 'Session' is used in different contexts in computer science e. I would discuss the sessions in context of web applications only. There are following fundamental points related to sessions in web applicaitons: 1. What is a session in web application? Why we need a session? How session creation and identification work? Where session data is stored? How to Delete a session?

Lets look at each part one-by-one: 1. What is a Session in Web Application? Web developer may need to store small data temporarily at server side, for each user who is interacting with the web application. Such data is stored in a session, so session is a temporary storage at web server. For each user, there is unique session are at server.

During request processing of a particular user, the user's session is accessable in all web pages i. The important point is, session is unique for each user. If there are 10 users interacting with the server, there would be 10 sessions created at server side we would shortly see how it is created , one for each user. Below picture explain this idea; there are 3 users i.

U1, U2, U3 interacting with the web-server, so there are 3 sessions at server side, one for each user i. If we save data in session for U1, it would be stored in S1 bucket or session. When we would get data for U1, it would be automatically read from S1 session. Later I have explained how server keep track of which session bucket, belong to which user. It allows one to be uniquely identified in a sea of millions of people.

You need to identify yourself every time you deal with the teller. If you got any questions or are unclear - please post comment and I will try to clear it up for you. The following is not strictly speaking, completely accurate in its terminology, but I hope it's helpful to you in understanding concepts. It's meant to represent the time between their first arrival at a page in the site until the time they stop using the site.

In practice, it's impossible to know when the user is done with the site. In most servers there's a timeout that automatically ends a session unless another page is requested by the same user. Like cookies, this usually doesn't get sent in the URL anymore because it's a security problem.

Instead it's stored along with a bunch of other stuff that collectively is also referred to as the session. Session variables are like cookies - they're name-value pairs sent along with a request for a page, and returned with the page from the server - but their names are defined in a web standard. Some session variables are passed as HTTP headers. They're passed back and forth behind the scenes of every page browse so they don't show up in the browser and tell everybody something that may be private.

Some web server software adds their own headers or transfer additional session data specific to the server software. But the standard ones are pretty well documented. HTTP is stateless connection protocol, that is, the server cannot differentiate between different connections of different users.

Hence comes cookie, once a client connects first time to a server, the server generates a new session id, which later will be sent to the client as cookie value. And from now on, this session id will identify that client connection, because within each HTTP request it will see the appropriate session id inside cookies. Now for each session id, the server keeps some data structure, which enables him to store data specific to user, this data structure you can abstractly call session.

Now, to remember different persons, A takes a photo of that person and keeps it. Each Person's pic has an ID number. And voila!! Same is with HTTP. It uses Sessions to record everything you did while using a website, and then, when you come again, it identifies you with the help of Cookies Cookie is like a token.

Picture is the Session here, and ID is the Cookie here. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. What are sessions? How do they work? Ask Question. Asked 11 years, 1 month ago. Active 3 months ago. Viewed k times. I am getting quite confused here. Need help. Improve this question. Rasmus Rasmus 7, 12 12 gold badges 45 45 silver badges 68 68 bronze badges. I wanted to understand web sessions too, now I understand.

I ended up writing my own wiki if that's of any help : machinesaredigging. In case if you don't know: storing password on client side is not safe, even if the password is hashed it doesn't make a difference, in fact.

Cracker can directly input the hashed password by creating a fake cookie There are better ways to store the login status. I written my own using protocol level details - bitspedia.

If a cookie expires before its associated session, that session becomes orphaned. If a session expires before its associated cookie, the servlet is not be able to find a session. At that point, a new session is automatically assigned when the request. You can set the maximum life of a cookie with the CookieMaxAgeSecs attribute in the session descriptor of the weblogic. User authentication information is stored both in the user's session data and in the context of a server or virtual host that is targeted by a Web application.

The session. If the server or virtual host is hosting only one Web application, the session. There are several Java methods and strategies you can use when using authentication with multiple Web applications. You use session persistence to permanently store data from an HTTP session object to enable failover and load balancing across a cluster of WebLogic Servers.

When your applications stores data in an HTTP session object, the data must be serializable. File, JDBC, cookie-based, and memory single-server, non-populated session persistence have some common properties. Each persistence method has its own set of attributes, as discussed in the following sections. These attributes are part of the session-param element, which is a child element of the session-descriptor element in the weblogic.

This section describes attributes common to file and JDBC-based persistence. These properties are only applicable if you are using session persistence:. Limits the number of cached sessions that can be active in memory at any one time. If you expect high volumes of simultaneous active sessions, you do not want these sessions to soak up the RAM of your server because this may cause performance problems swapping to and from virtual memory.

When the cache is full, the least recently used sessions are stored in the persistent store and recalled automatically when required. If you do not use persistence, this property is ignored, and there is no soft limit to the number of sessions allowed in main memory.

By default, the number of cached sessions is To turn off caching, set this to 0. It is not applicable for other persistence types. Sets the time, in seconds, that WebLogic Server waits between doing house-cleaning checks for timed-out and invalid sessions, and deleting the old sessions and freeing up memory.

Use this attribute to tune WebLogic Server for best performance on high traffic sites. The minimum value is every second 1. The maximum value is once a week , seconds. If not set, the attribute defaults to 60 seconds. When you use memory-based storage, all session information is stored in memory and is lost when you stop and restart WebLogic Server. Note: If you do not allocate sufficient heap size when running WebLogic Server, your server may run out of memory under heavy load.

Note: You must create this directory yourself and make sure appropriate access privileges have been assigned to the directory. JDBC persistence stores session data in a database table using a schema provided for this purpose.

You can use any database for which you have a JDBC driver. You configure database access by using connection pools. Because WebLogic Server uses the system time to determine the session lifetime when using JDBC session persistence, you must be sure to synchronize the system clock on all of the machines on which servers are running in the same cluster.