Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.
116
Chapter 5 Accessing the Standard CGI Variables
5.1 Servlet Equivalent of CGI 
Variables
For each standard CGI variable, this section summarizes its purpose and the
means of accessing it from a servlet. As usual, once you are familiar with this
information, you may want to use Appendix A (Servlet and JSP Quick
Reference) as a reminder. Assume 
request
 is the 
HttpServletRequest
supplied to the 
doGet
 and 
doPost
 methods.
AUTH_TYPE
If an 
Authorization
 header was supplied, this variable gives the 
scheme specified (
basic
 or 
digest
). Access it with 
request.getAu 
thType()
.
CONTENT_LENGTH
For 
POST
 requests only, this variable stores the number of bytes of data 
sent, as given by the 
Content Length
 request header. Technically, 
since the 
CONTENT_LENGTH
 CGI variable is a string, the servlet 
equivalent is
 String.valueOf(request.getContentLength())
 or 
request.getHeader("Content Length")
. You ll probably want to 
just call
 request.getContentLength()
, which returns an 
int
. 
CONTENT_TYPE
CONTENT_TYPE
 designates the MIME type of attached data, if specified. 
See Table 7.1 in Section 7.2 (HTTP 1.1 Response Headers and Their 
Meaning) for the names and meanings of the common MIME types. 
Access 
CONTENT_TYPE
 with 
request.getContentType()
.
 DOCUMENT_ROOT
The 
DOCUMENT_ROOT
 variable specifies the real directory corresponding 
to the URL 
http://host/
. Access it with 
getServletContext().getRealPath("/")
. In older servlet specifica 
tions you accessed this variable with 
request.getRealPath("/")
; the 
older access method is no longer supported. Also, you can use 
get 
ServletContext().getRealPath
 to map an arbitrary URI (i.e., URL 
suffix that comes after the hostname and port) to an actual path on the 
local machine.
Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.
Servlet and JSP training courses by book's author: courses.coreservlets.com.






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