Dark Horse day06 EL expression operator & amp; 11 built-in Map objects, dark horse day06el expression

Dark Horse day06 EL expression operator & 11 built-in Map objects, dark horse day06el expression
1. I don't want to think much about EL expression operations. Let's look at the example directly ....

<% @ Page language = "java" import = "java. util. *" pageEncoding = "UTF-8" %> <! Doctype html public "-// W3C // dtd html 4.01 Transitional // EN"> Result:

2. 11 built-in objects of EL.
Do not confuse the nine built-in objects of jsp. The nine built-in objects of jsp are domain objects, while the 11 built-in objects of EL are corresponding map. A set is displayed instantly.
Get common development objects: el has 11 built-in objects, which can be directly used in el without prior definition.
! PageContext -- with this feature, you can easily obtain the Nine hidden objects in the jsp page.

! Pagination -- Map composed of attributes in the page domain
! RequestScope -- Map composed of attributes in the request domain
! SessionScope -- Map composed of attributes in the session domain
! ApplicationScope -- Map composed of attributes in the application domain

! Param -- Map composed of all request parameters <String, String>
ParamValues -- Map composed of all request parameters <String, String []>

Header -- Map composed of all request headers <String, String>
HeaderValues -- Map composed of all request headers <String, String []>

! Cookie-Map composed of all cookie Information <String, Cookie>

InitParam -- the initialization parameters of all web applications constitute a Map
Case:

<% @ Page language = "java" import = "java. util. *" pageEncoding = "UTF-8" %> <! Doctype html public "-// W3C // dtd html 4.01 Transitional // EN"> Running result: