You want the client (the browser) to remember some bit of information for you.
Bake a cookie, and serve it to the client along with your response.
Cookies were invented by Netscape as a debugging technique, but have
since become ubiquitous: all modern browsers, including MSIE, and
text browsers such as Lynx accept and store them. A cookie is, at
heart, a small piece of text -- a name and value pair -- that
the server side generates and sends to the client. The browser
remembers them (nontransient cookies are stored to your hard disk;
Netscape creates a file called
cookies.txt, for example). The browser then
sends them back to the server on any subsequent visit to a page from
the same site. The
Cookie class is part of the
javax.servlet.http package, so any
servlet implementation will include it. The
constructor is passed a name and value, but there are other
parameters you can set. Most
important is the expiry time, which is
in seconds from the time you first send it. The default is -1; if the
value is negative, the cookie is not saved to disk; it becomes a
"transient cookie” that exists only
until the browser exits and is then forgotten. For cookies that are
stored to disk, the expiry time is converted to a base of January 1,
1970, the beginning of Unix time and of the modern computing era.
When the browser visits a site that has sent it a cookie or cookies, it returns all of them as part of the HTTP headers. You retrieve them all (as ...