Nine types of JSP objects

I will briefly describe nine types of JSP objects:
Page
Application
Request
Response
Session
Config
Out
Pagecontext
 
Page
<% @ Page contenttype = "text/html; charset = gb2312" Language = "Java" Import = "Java. SQL. *" %>

Response
<%
Response. setheader ("Pragma", "No-Cache ");
Response. setheader ("cache-control", "No-Cache ");
Response. setdateheader ("expires", 0 );
%>

<% Response. sendredirect ("login. jsp"); %>

Session
<% Session. invalidate (); %>

Request/session
<%
String errmsg = request. getparameter ("errmsg ");
Request. getsession (true );
String chk = "false ";
Session. putvalue ("enter", chk );
%>

Out
<%
If (errmsg! = NULL & errmsg. Equals ("error1 "))
Out. Print ("your user number has not been activated !! ");
Else if (errmsg! = NULL & errmsg. Equals ("error2 "))
Out. Print ("the Administrator account or password you entered is incorrect !! ");
%>

The description of the request object in Java Doc is as follows: