Request,session,application, three comparisons

Scope::

Request < Session < application

Each corresponding interface

The interface that corresponds to the request object:

Javax.servlet.ServletRequest its sub-interface:javax.servlet.http.HttpServletRequest

Interface for session object:javax.servlet.http.HttpSession

Interface for application objects:javax.servlet.ServletContext

Three common methods:

SetAttribute (string name, Object o), getattribute (string name);

Simple analysis of three people:

1.request

Call the above two methods, only on a single request (forwarding not count the request, because the forwarding is the server-side behavior) in effect, when the information returned to the client, the object is destroyed

2.session

Concept:

is the server-side behavior

Used to track the status of the customer, when the user to visit a site, the server will generate a SessionID for the customer, in a cookie way to return to the client, when the customer to visit the site's other services, will bring the current SessionID Together to make a request, has identified which user, a user is like a Session object, do not interfere.

Operating mechanism:

Session Failure Reason:

1) Session expires

2) server-side call invalidate () to invalidate it

3) Now the majority of the page is to support the session, to let the page lose the session effect,

Add <%@ page session= "false" to%>, but this is not normally done

Important methods of Session:

1) getId ()---Get the ID number of the session, each ID number is different

2) isnew ()---Judge if the session is new

3) Invalidate ()---Let the current session expire and release resources

4) setmaxinactiveinterval (int interval)---Set the time interval (in seconds) at which the session is inactive.

Over that time, the session expires,

If you set a negative number, or 0, you do not limit the session inactivity interval, which is typically 30 minutes by default

5) SetAttribute (string name, Object o), getattribute (string name)

Application Scenarios:

1) Login

2) Shopping Cart

3.application

call the above two methods , a server on a Application object, the user shared a application, when the server stopped application was destroyed, (for site visits)

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Transfer from http://blog.csdn.net/hzc543806053/article/details/7416007

Request,session,application, three comparisons