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Hi Alaric
Alaric said:
> GETs are supposed to be idempotent; caches are welcome to cache GET
requests
> and service later requests to that resource without hitting the server
again,
> etc. In most cases, the only difference between performing one GET and
> performing two GETs should be in the server's logs!
>
> POSTs are assumed to have some effect upon the world, so that performing
two
> POSTs is not necessarily the same as performing one POST.
Didier replies:
I agree, but a cache bring other side effects like not having the latest up
to date document. If the HTTP GET includes parameters then two consecutive
HTTP GET may not have the same state too.
Alaric said:
> There's nothing stopping developers from making 'GET
> http://www.missiles.gov/launch' destroy the world, and requiring people to
do
> a POST to some URL (perhaps even the same URL!) to find out the current
> weather in Alaska, indeed.
Didier replies:
Exactly since the GET method can be overloaded by a script. So is the POST
method. Nothing prevent a weird developer to have a GET act as a POST and a
POST act as a GET. This is at least the current potential imposed by the
actual servers.
Alaric said:
> But by convention, 'fetching a[n XML] document' ought to be done with GET,
> and things involving activating behaviour (RPCs, basically, although
people
> here get a bit touchy about that word) done with POST, and things
involving
> overwriting a document with PUT, and so on.
Didier replies:
Yes the RFC specify that GET is to be used to fetch documents but do not
impose that a POST modify anything on the server. As a reminder, the RFC is
located at: http://www.w3.org/Protocols/HTTP/1.1/rfc2616.pdf. I posted an
extract below as reference.
POST:
The POST method is used to request that the origin server accept the entity
enclosed in the request as a new
subordinate of the resource identified by the Request-URI in the
Request-Line. POST is designed to allow a
uniform method to cover the following functions:
· Annotation of existing resources;
· Posting a message to a bulletin board, newsgroup, mailing list, or similar
group of articles;
· Providing a block of data, such as the result of submitting a form, to a
data-handling process;
· Extending a database through an append operation.
***The actual function performed by the POST method is determined by the
server and is usually dependent on the
Request-URI*** The posted entity is subordinate to that URI in the same way
that a file is subordinate to a directory
containing it, a news article is subordinate to a newsgroup to which it is
posted, or a record is subordinate to a
database.
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