Sessions are maintained automatically by a session cookie that is sent to the client when the session is first created. The session cookie contains the session ID, which identifies the client to the browser on each successive interaction.
You can configure whether and how sessions use cookies. See the session-properties and cookie-properties elements in the sun-web. You can configure whether sessions use URL rewriting. See the session-properties element in the sun-web. Once a session has been created the application user is authenticated if authentication is used and logged in to the session. Each interaction step from the servlet that receives an EJB request does two things: generates content for a JSP to format the output, and checks that the user is properly authenticated.
Additionally, you can specify that a session cookie is only passed on a secured connection that is, HTTPS , so the session can only remain active on a secure channel. For more information about security, see Chapter 5, "Securing Web Applications". To use a session, first create a session using the HttpServletRequest method getSession. Once the session is established, examine and set its properties using the provided methods.
If desired, set the session to time out after being inactive for a defined time period or invalidate it manually. You can also bind objects to the session which store them for use by other components. To create a new session or to gain access to an existing session, use the HttpServletRequest method getSession , as shown in the following example:.
Calling the method with no arguments, creates a session if one does not already exist which is associated with the request. Additionally, calling the method with a Boolean argument creates a session only if the argument is true. Note that, the false parameter to getSession prevents the servlet from creating a new session if one does not already exist:.
The getSession method should be called before anything is written to the response stream. For more information about getSession , see the Java Servlet Specification v2. Once a session ID has been established, use the methods in the HttpSession interface to examine session properties, and methods in the HttpServletRequest interface to examine request properties that relate to the session. The following table shows the methods to examine session properties. The left column lists HttpSession methods, and the right column lists descriptions of these methods.
Returns the session time in milliseconds since January 1, , GMT. Returns the assigned session identifier. Returns the last time the client sent a request carrying the assigned session identifier or -1 if its a new session in milliseconds since January 1, , GMT. Active 6 months ago. Viewed times. When user requests a webpage it sends all the cookies available for that browser on the PC. Is there something I am not understanding? Improve this question.
Pree Pree 43 4 4 bronze badges. Add a comment. Active Oldest Votes. These are separate concepts: Cookie - Browser sends this with every request automatically Header - Part of a HTTP request, the browser will only send data here if instructed. If the user doesn't have an access token, they can use the session to get a new token. Improve this answer. Warren Parad Warren Parad 2, 17 17 silver badges 25 25 bronze badges. Because: There may be, and probably is, sensitive data in that session, e.
If you just stored the user's id in a cookie, the user could manipulate it and easily pose as anyone else. There are of course ways to mitigate that, but simply not allowing the user to futz with the cookie contents because it's just a meaningless session id is the simplest.
It allows the server to manage session state; e. It helps to demystify Sessions. One question: where in memory is the session typically stored on the server? Main memory would be OK for a small site that need only handle perhaps a thousand sessions concurrently but what happens when there are many thousands of concurrent sessions? Can sessions be easily linked to a database? 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. In a stateless environment, an application may need to repeat an expensive operation. An example might be a financial calculation that requires many SQL statements and calls to mathematics libraries before displaying the results on several web pages.
An application that uses a session variable to remember the result exposes the user, and the server, to the cost of the calculation only once. Often a database application—or indeed any application—needs to present a series of screens in a controlled order. One style of application—known as a wizard —guides a user through what would otherwise be a complex task with a series of screens.
Wizards are sometimes used for complex configurations, such as some software installations, and often alter the flow of screens based on user input. Some applications require that a user enter via a known page. Applications, such as online banking, often force a user to enter via a login page rather than allow access directly to a function such as funds transfer.
Many database applications validate data before creating or updating a record in the database, preventing erroneous data from being saved. Sessions can keep the intermediate data, so that incomplete data can be edited—rather that rekeyed—when errors are detected.
In the case study, the fields entered by the user are held in an array as a session variable until the validation is successful. Another example where intermediate results can be used is when a database application collects and validates data for a single record over a number of fill-in forms. A shopping cart is an example where complete data may not be created until a user requests a purchase.
The winestore application doesn't implement the shopping cart this way; rather, a shopping cart is implemented by creating a row in the orders table and adding rows to the items table as items are selected. We develop the shopping cart in Chapter Sessions can personalize a web site. Personalization not only includes background color or layout alternatives, but can include recording a user's interests and modifying searches.
The winestore application can record favorite regions or a buyer's price range as session variables; each query could then be modified to reflect these settings.
0コメント