AB Infinity feb 2014 | Página 2

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Chapter

I

f you come to servlets with a background in traditional Common Gateway Interface (CGI) programming, you are probably used to the idea of
“CGI variables.” These are a somewhat eclectic collection of information about the current request. Some are based on the HTTP request line
and headers (e.g., form data), others are derived from the socket itself (e.g.,
the name and IP address of the requesting host), and still others are taken
from server installation parameters (e.g., the mapping of URLs to actual
paths).
Although it probably makes more sense to think of different sources of
data (request data, server information, etc.) as distinct, experienced CGI programmers may find it useful to see the servlet equivalent of each of the CGI
variables. If you don’t have a background in traditional CGI, first, count your
blessings; servlets are easier to use, more flexible and more efficient than
standard CGI. Second, just skim this chapter, noting the parts not directly
related to the incoming HTTP request. In particular, observe that you can
use getServletContext().getRealPath to map a URI (the part of the
URL that comes after the host and port) to an actual path and that you can
use request.getRemoteHost and request.getRemoteAddress to get the
name and IP address of the client.

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