Application object and session object in detail?

Answer 1

Session ObjectThe session implicit object is used to provide an association between the client and the server. This association, or session, persists over multiple connections and/or requests during a given time period. Sessions are used to maintain state and user identity across multiple page requests.

A session can be maintained either by using cookies or by URL rewriting. To expose whether the client supports cookies, session defines an isCookieSupportDetermined() method and an isUsingCookies() method.

Servlet Class

HttpSession

The following table summarises the most useful methods available to the session object. For more details consult the Servlet API.MethodDescriptionisNew()A session is considered to be "new" if it has been created by the server, but the client has not yet acknowledged joining the session.invalidate()Discards the session, releasing any objects stored as attributes.getAttribute(String)Retrives the object associated with the named attribute.getAttributeNames()Retrives the names of all attributes currently associated with the session.setAttribute(String, object)Sets the object to the named attribute. attribute created if it doesn't exist.removeAttribute(String)Removes the object bound with the specified name from this session.

Application ObjectThis implicit object represents the application to which the JSP belongs. JSPs are grouped into applications according to their URLs where the first directory name in a URL defines the application.

The application object contains methods that provide information about the JSP Container, support for logging plus utility methods for example translating a relative URL to an absolute path.

Servlet Class

javax.servlet.ServletContext

The following table summarises the most useful methods available to the session object. For more details consult the Servlet API.MethodDescriptiongetAttribute(String objName)Returns the object named objName or returns null if the objName does not exist.getAttributeNames()Returns an Enumeration containing the attribute names available within the application.setAttribute(String objName, Object object)Stores the object with the given object name in this application.removeAttribute(String objName)Removes the objName object from the application.getMajorVersion()Returns the major version of the Servlet API for the JSP COntainer.getServerInfo()Returns information about the JSP Container, typically, name and product version.getResourceAsStream(Path)Translates the resource URL into an input stream for reading.log(Message)Writes a text string to the JSP Containers default log file.