Request Parameters
Besides the URI and headers, a request message can contain additional information in the form of parameters. If the URI identifies a server-side program for displaying weather information, for example, request parameters can provide information about which city the user wants to see a forecast for. In an e-commerce application, the URI may identify a program that processes orders, using the customer number and the list of items to be purchased as parameters.
Parameters can be sent in one of two ways: tacked on to the URI in the form of a query string or sent as part of the request message body. This is an example of a URL with a query string:
http://www.weather.com/forecast?city=Hermosa+Beach&state=CA
The query string starts with a question mark (?
)
and consists of name/value pairs separated by ampersands
(&
). These names and values must
be URL-encoded,
meaning that special characters, such as whitespace, question marks,
ampersands, and all other nonalphanumeric characters are encoded so
that they don’t get confused with characters used to
separate name/value pairs and other parts of the URI. In this
example, the space between Hermosa
and
Beach
is encoded as a plus sign. Other special
characters are encoded as their corresponding hexadecimal ASCII
value; for instance, a question mark is encoded as
%3F
. When parameters are sent as part of the
request body, they follow the same syntax: URL-encoded name/value
pairs separated by ampersands.
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