All,
here is the issue with the POST on the shopping cart to place the order:
REST constrains messages to be stateless. The meaning of the message must not depend on server side state.
The meaning of the message depends on the semantics of the resource (which is constrained to be constant over time) but it must not depend on the resource's state at some point in time.
This is why, in order to correctly reflect the intention to buy A,B and C (see earlier example[1]) these items must be enumerated in the POST body. Just POSTing to the cart resource makes the meaning of the message a function of the semantics of the resource BUT NOT of its current state.
Jan
[1]
https://jersey.dev.java.net/servlets/ReadMsg?list=users&msgNo=10255
On Feb 18, 2010, at 4:03 PM, Jan Algermissen wrote:
>
> On Feb 18, 2010, at 3:36 PM, Jan Algermissen wrote:
>
>>
>> On Feb 18, 2010, at 3:32 PM, Jan Algermissen wrote:
>>
>>>
>>>
>>> for purposes of visibility but I just saw Mark B mentioning that and cannot give an explanation.
>>>
>>
>> Here is the short thread: <http://tech.groups.yahoo.com/group/rest-discuss/message/13627>
>
> Re-reading that, there are two issues
>
> - I am not sure I agree and if I do I cannot completely explain on what grounds
> - There indeed is an issue with how much the client wants to rely on the server
> maintining stability of the cart (or order) when it comes to
> me hitting 'submit'. IOW, how can I be sure the resource state is the same
> when the POST arives as it was when I sent the request
> - the issue has consequences on the design of e.g. the payment 'operation'
> that started this thread.
> Mark's position emphasizes that the complete order should be sent to a
> payment resource instead of invoking a POST-tunneled pay() on the order.
>
> Jan
>
>>
>>
>>
>>> Jan
>>>
>>>
>>>> In my view, creating resources identifiers for things of interest is precisely how you avoid relying on sessions. The service will associate that resource identifier with objects stored in a database, and there's no need for the client to store anything once it gets that resource identifier.
>>>>
>>>> By analogy, let's say you call your insurance company to file a claim. The first time you call, you give them all your info and they give you a claim number (a resource identifier!). Next time you call, it does not really matter who you talk to as long as you give them the claim number and they can look it up in their database. Without a claim number, you'd need to start all over or talk to the same person to continue the session --and that wouldn't very RESTful.
>>>>
>>>> I'm not sure I can comment on your API specifically, but I believe you can build the system the way you want without relying on sessions.
>>>>
>>>> -- Santiago
>>>>
>>>>
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>>>
>>> -----------------------------------
>>> Jan Algermissen, Consultant
>>> NORD Software Consulting
>>>
>>> Mail: algermissen_at_acm.org
>>> Blog: http://www.nordsc.com/blog/
>>> Work: http://www.nordsc.com/
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>>
>> -----------------------------------
>> Jan Algermissen, Consultant
>> NORD Software Consulting
>>
>> Mail: algermissen_at_acm.org
>> Blog: http://www.nordsc.com/blog/
>> Work: http://www.nordsc.com/
>> -----------------------------------
>>
>>
>>
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>
> -----------------------------------
> Jan Algermissen, Consultant
> NORD Software Consulting
>
> Mail: algermissen_at_acm.org
> Blog: http://www.nordsc.com/blog/
> Work: http://www.nordsc.com/
> -----------------------------------
>
>
>
>
>
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-----------------------------------
Jan Algermissen, Consultant
NORD Software Consulting
Mail: algermissen_at_acm.org
Blog:
http://www.nordsc.com/blog/
Work:
http://www.nordsc.com/
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