How to retrieve HTML form parameters from the request ?

All form data from both the query string + post body are aggregated into the request parameter set.
The parameters sent in URI query string are stored by the servlet container as a set of name/value pairs.

Multiple parameter values can exist for any given parameter name. (Like, a=123&a=567)
 
Methods in ServletRequest interface

• getParameter : returns value for a given parameter
• getParameterNames : returns array of all names of parameters (No value)
• getParameterValues : returns an array of String objects containing all the parameter values associated with a parameter name

Scenario : If a request is made with :

• A query string of a=hello
  and
• A post body of a=goodbye&a=world

The resulting parameter set would be ordered a=(hello, goodbye, world)