Basic usage, principle and details of session

Session tracking technology stored on the server

JavaEE Provide HttpSession Interface ,Session Similar to a domain on the server

Basic use ：

establish Session object ：

HttpSession session = request.getSession()

session.setAttribute(String name,Object o) Store in Session domain

session.getAttribute(String name) Get by key Session Data in domain

session.removeAttribute(String name) Delete Session Data in domain

Case study ：

principle ：

Session Is based on Cookie Realized , Exists in the program Session when ,Tomcat Will automatically detect , And create the corresponding response header set-Cookie：JSSESSIONID = ...  Send it to the browser , The browser wants to access Session The request header will be issued when the domain Cookie: JSSESSIONID = …, Not like Cookie Send data directly .

 

 

details ：

Session Activation of , passivation ：

Session It will not disappear immediately after the server is shut down normally ,

passivation ：

When the server is shut down normally ,Session Store the data in the hard disk of the server ,target/work Under the folder

activation ：

When the server starts again ,Session Re extract the data stored in the hard disk Session data , establish Session Domain , Delete the files stored on the hard disk

Session Survival time ：

The default is 30 minute

It can be configured in Web.xml Configure lifetime

<session-config>

<session-timeout>90</session-timeout>

</session-config>

Delete Session：

session.invalidate();

effect ： Exit account