The Role of Form Data If you’ve ever used a search engine, visited an online bookstore, tracked stocks on the Web, or asked a Web-based site for quotes on plane tickets
computer science
Description
The Role of Form Data
If you’ve ever used a search engine, visited an online bookstore, tracked stocks on the
Web, or asked a Web-based site for quotes on plane tickets, you’ve probably seen
funny-looking URLs like http://host/path?user=Marty+Hall&origin=bwi&dest=sfo.
The part after the question mark (i.e., user=Marty+Hall&origin=bwi&dest=sfo) is
known as form data (or query data) and is the most common way to get information
from a Web page to a server-side program. Form data can be attached to the end of
the URL after a question mark (as above) for GET requests; form data can also be
sent to the server on a separate line for POST requests. If you’re not familiar with HTML forms, Chapter 19 (Creating and Processing HTML Forms) gives details on
how to build forms that collect and transmit data of this sort. However, here are the
basics
Extracting the needed information from this form data is traditionally one of the
most tedious parts of server-side programming.
First of all, before servlets you generally had to read the data one way for GET
requests (in traditional CGI, this is usually through the QUERY_STRING environment variable) and a different way for POST requests (by reading the standard input
in traditional CGI).
Second, you have to chop the pairs at the ampersands, then separate the parameter names (left of the equal signs) from the parameter values (right of the equal
signs).
