THE STRUCTURE OF HTTP REQUESTS - HTTP Programming Recipes for Java Bots - page 9

The response from the web server, to the GET and POST requests is the same. In
both cases, the response will be an HTML file, image, or some other form of data. What is
returned depends on what the web server is programmed to return for the request it has
received. The usual response to a POST will be a HTML page that displays the result of the
form. For example, the response to a POST from an order form might be a HTML page that
contains the user's order number.
In the next few sections how the GET and POST requests work will be explained in
greater detail.
GET Requests
Choosing between GET and POST usually comes down to how much data must pass to
the web site. GET allows only a limited amount of data to be passed to the web server. POST
allows a nearly infinite amount of data to be passed to the web server. However, if you are
writing an HTTP program to communicate with an existing web site, the choice is not yours.
You must conform to what that site expects. Therefore, most HTTP applications will need to
support a mix of GET and POST requests.
The GET request is good for when little, or no, additional information must be sent to the
web server with a request. For example, the following URL, if sent with a GET request, will
pass no data to the web server.
http://www.httprecipes.com/1/test.php
The above URL simply requests the test.php page and does not pass any arguments
on to the page. However, several arguments may need to be passed. What if the bot needed to
pass two arguments named “ first ” and “ last ”? The following URL would do this:
http://www.httprecipes.com/1/test.php?first=Jeff&last=Heaton
This would pass two arguments to the test.php page. As can be seen, passing argu-
ments with a GET request requires them to be appended onto the URL. The question mark
(?) indicates that the arguments have started. Each argument is the name of the argument,
followed by an equal sign (=), followed by the value of the argument. Each argument is sepa-
rated from the other arguments using an ampersand (&) symbol.
If there are a large number of arguments to pass, GET can be cumbersome. In such
cases, the POST request should be considered. Of course, as previously stated, if using an
existing web site, the bot must conform to what request type is already being used.