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244

Chapter 10 JSP Scripting Elements

Special Declaration Syntax

As with scriptlets, if you want to use the characters 

%>

, enter 

%\>

 instead.

Finally, note that the XML equivalent of 

<%! Code %>

 is 

Code

10.5 Predefined Variables

To simplify code in JSP expressions and scriptlets, you are supplied with eight

automatically defined variables, sometimes called implicit objects. Since JSP

declarations (see Section 10.4) result in code that appears outside of the

_jspService

 method, these variables are not accessible in declarations. The

available variables are 

request

, 

response

, 

out

, 

session

, 

application

,

config

, 

pageContext

, and 

page

. Details for each are given below. 

request

This variable is the 

HttpServletRequest

 associated with the request; 

it gives you access to the request parameters, the request type (e.g., 

GET

or 

POST

), and the incoming HTTP headers (e.g., cookies). Strictly 

speaking, if the protocol in the request is something other than HTTP, 

request

 is allowed to be a subclass of 

ServletRequest

 other than 

HttpServletRequest

. However, few, if any, JSP servers currently sup 

port non HTTP servlets. 

response

This variable is the 

HttpServletResponse

 associated with the 

response to the client. Note that since the output stream (see 

out

) is 

normally buffered, it is legal to set HTTP status codes and response 

headers in JSP pages, even though the setting of headers or status codes 

is not permitted in servlets once any output has been sent to the client. 

out

This is the 

PrintWriter

 used to send output to the client. However, to 

make the 

response

 object useful, this is a buffered version of 

Print 

Writer

 called 

JspWriter

. You can adjust the buffer size through use of 

the 

buffer

 attribute of the 

page

 directive (see Section 11.5). Also note 

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