<s>
In	O
web	O
development	O
,	O
a	O
postback	B-Application
is	O
an	O
HTTP	B-Protocol
POST	I-Protocol
to	O
the	O
same	O
page	O
that	O
the	O
form	B-General_Concept
is	O
on	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
the	O
contents	O
of	O
the	O
form	B-General_Concept
are	O
POSTed	O
back	O
to	O
the	O
same	O
URL	O
as	O
the	O
form	B-General_Concept
.	O
</s>
<s>
Postbacks	B-Application
are	O
commonly	O
seen	O
in	O
edit	O
forms	O
,	O
where	O
the	O
user	O
introduces	O
information	O
in	O
a	O
form	B-General_Concept
and	O
hits	O
"	O
save	O
"	O
or	O
"	O
submit	O
"	O
,	O
causing	O
a	O
postback	B-Application
.	O
</s>
<s>
Postbacks	B-Application
are	O
most	O
commonly	O
discussed	O
in	O
relation	O
to	O
JSF	B-Language
and	O
ASP	B-General_Concept
or	O
ASP.NET	B-Application
.	O
</s>
<s>
In	O
ASP	B-General_Concept
,	O
a	O
form	B-General_Concept
and	O
its	O
POST	O
action	O
have	O
to	O
be	O
created	O
as	O
two	O
separate	O
pages	O
,	O
resulting	O
in	O
the	O
need	O
for	O
an	O
intermediate	O
page	O
and	O
a	O
redirect	O
if	O
one	O
simply	O
wants	O
to	O
perform	O
a	O
postback	B-Application
.	O
</s>
<s>
This	O
problem	O
was	O
addressed	O
in	O
ASP.NET	B-Application
with	O
the	O
__doPostBack( )	O
function	O
and	O
an	O
application	O
model	O
that	O
allows	O
a	O
page	O
to	O
perform	O
validation	O
and	O
processing	O
on	O
its	O
own	O
form	B-General_Concept
data	O
.	O
</s>
<s>
In	O
JSF	B-Language
,	O
postbacks	B-Application
trigger	O
the	O
full	O
JSF	B-Language
life-cycle	O
,	O
which	O
just	O
like	O
ASP.NET	B-Application
performs	O
conversion	O
and	O
validation	O
of	O
the	O
form	B-General_Concept
data	O
that	O
was	O
included	O
in	O
the	O
postback	B-Application
.	O
</s>
<s>
Various	O
utility	O
methods	O
are	O
present	O
in	O
the	O
JSF	B-Language
API	O
to	O
programmatically	O
check	O
if	O
a	O
given	O
request	O
is	O
a	O
postback	B-Application
or	O
not	O
.	O
</s>
